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.\" RCSid "$Id$" |
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.\" Print using the -ms macro package |
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.DA 1/20/99 |
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.tl """Copyright \(co 2003 Regents, University of California |
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.sp 2 |
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.TL |
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The |
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.so ../src/rt/VERSION |
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.br |
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Synthetic Imaging System |
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.AU |
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1.4 |
Building Technologies Department |
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.br |
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Lawrence Berkeley Laboratory |
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.br |
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1 Cyclotron Rd., MS 90-3111 |
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.br |
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Berkeley, CA 94720 |
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.NH 1 |
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Introduction |
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.PP |
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RADIANCE was developed as a research tool |
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for predicting the distribution of visible radiation in |
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illuminated spaces. |
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It takes as input a three-dimensional geometric model of |
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the physical environment, and produces a map of |
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spectral radiance values in a color image. |
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The technique of ray-tracing follows light backwards |
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from the image plane to the source(s). |
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Because it can produce realistic images from a simple description, |
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RADIANCE has a wide range of applications in graphic arts, |
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lighting design, computer-aided engineering and architecture. |
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.KF |
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.sp 25 |
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.ce |
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.B "Figure 1." |
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.sp |
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.KE |
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.PP |
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The diagram in Figure 1 shows the flow between programs (boxes) and |
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data (ovals). |
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The central program is |
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.I rpict, |
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which produces a picture from a scene description. |
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.I Rview |
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is a variation of |
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.I rpict |
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that computes and displays images interactively. |
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greg |
1.4 |
Other programs (not shown) connect many of these elements together, |
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such as the executive programs |
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.I rad |
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and |
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.I ranimate, |
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the interactive rendering program |
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.I rholo, |
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and the animation program |
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.I ranimove. |
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The program |
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.I obj2mesh |
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acts as both a converter and scene compiler, converting a Wavefront .OBJ |
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file into a compiled mesh octree for efficient rendering. |
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1.1 |
.PP |
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A scene description file lists the surfaces and materials |
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1.4 |
that make up a specific environment. |
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The current surface types are spheres, polygons, cones, and cylinders. |
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There is also a composite surface type, called mesh, and a pseudosurface |
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type, called instance, which facilitates very complex geometries. |
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Surfaces can be made from materials such as plastic, metal, and glass. |
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Light sources can be distant disks as well as local spheres, disks |
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and polygons. |
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1.1 |
.PP |
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From a three-dimensional scene description and a specified view, |
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.I rpict |
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produces a two-dimensional image. |
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A picture file is a compressed binary representation of the |
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pixels in the image. |
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This picture can be scaled in size and |
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brightness, anti-aliased, and sent to a graphics output device. |
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.PP |
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A header in each picture file lists the program(s) and |
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parameters that produced it. |
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This is useful for identifying a picture |
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without having to display it. |
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The information can be read by the program |
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.I getinfo. |
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.NH 1 |
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Scene Description |
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.PP |
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A scene description file represents a |
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three-dimensional physical environment |
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in Cartesian (rectilinear) world coordinates. |
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It is stored as ASCII text, with the following basic format: |
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.DS |
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# comment |
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modifier type identifier |
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1.4 |
n S1 S2 "S 3" .. Sn |
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1.1 |
0 |
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m R1 R2 R3 .. Rm |
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modifier alias identifier reference |
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! command |
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... |
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.DE |
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.PP |
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A comment line begins with a pound sign, `#'. |
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.PP |
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The scene description |
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.I primitives |
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all have the same general format, and can |
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be either surfaces or modifiers. |
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A primitive has a modifier, a type, and an identifier. |
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A modifier is either the identifier of a |
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.I "previously defined" |
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primitive, or "void"\(dg. |
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.FS |
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\(dgThe most recent definition of a modifier is the one used, |
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and later definitions do not cause relinking of loaded |
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primitives. |
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Thus, the same identifier may be used repeatedly, and each new |
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definition will apply to the primitives following it. |
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.FE |
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1.4 |
An identifier can be any string (i.e., any sequence of non-white characters). |
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1.1 |
The |
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.I arguments |
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associated with a primitive can be strings or real numbers. |
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The first integer following the identifier is the number |
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of string arguments, and it is followed by the arguments themselves |
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1.4 |
(separated by white space or enclosed in quotes). |
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1.1 |
The next integer is the number of integer arguments, and is followed |
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by the integer arguments. |
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(There are currently no primitives that use them, however.) |
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The next integer is the real argument count, and it is followed |
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by the real arguments. |
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.PP |
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An alias gets its type and arguments from a previously defined primitive. |
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This is useful when the same material is used with a different |
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modifier, or as a convenient naming mechanism. |
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1.2 |
The reserved modifier name "inherit" may be used to specificy that |
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an alias will inherit its modifier from the original. |
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1.1 |
Surfaces cannot be aliased. |
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.PP |
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A line beginning with an exclamation point, `!', |
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is interpreted as a command. |
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It is executed by the shell, and its output is read as input to |
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the program. |
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The command must not try to read from its standard input, or |
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confusion will result. |
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A command may be continued over multiple lines using a backslash, `\\', |
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to escape the newline. |
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.PP |
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1.4 |
White space is generally ignored, except as a separator. |
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1.1 |
The exception is the newline character after a command or comment. |
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Commands, comments and primitives may appear in any combination, so long |
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as they are not intermingled. |
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.NH 2 |
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Primitive Types |
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.PP |
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Primitives can be surfaces, materials, textures or patterns. |
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1.4 |
Modifiers can be materials, mixtures, textures or patterns. |
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1.1 |
Simple surfaces must have one material in their modifier list. |
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.NH 3 |
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Surfaces |
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.PP |
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A scene description will consist mostly of surfaces. |
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The basic types are given below. |
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.LP |
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.UL Source |
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.PP |
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A source is not really a surface, but a solid angle. |
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It is used for specifying light sources that are very distant. |
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The direction to the center of the source and the number of degrees |
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subtended by its disk are given as follows: |
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.DS |
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mod source id |
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0 |
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0 |
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4 xdir ydir zdir angle |
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.DE |
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.LP |
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.UL Sphere |
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.PP |
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A sphere is given by its center and radius: |
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.DS |
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mod sphere id |
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0 |
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0 |
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4 xcent ycent zcent radius |
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.DE |
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.LP |
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.UL Bubble |
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.PP |
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A bubble is simply a sphere whose surface normal points inward. |
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.LP |
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.UL Polygon |
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.PP |
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A polygon is given by a list of three-dimensional vertices, |
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which are ordered counter-clockwise as viewed from |
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the front side (into the surface normal). |
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The last vertex is automatically connected to the first. |
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Holes are represented in polygons as interior vertices connected to |
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the outer perimeter by coincident edges (seams). |
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.DS |
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mod polygon id |
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0 |
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0 |
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3n |
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x1 y1 z1 |
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x2 y2 z2 |
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... |
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xn yn zn |
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.DE |
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.LP |
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.UL Cone |
218 |
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.PP |
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A cone is a megaphone-shaped object. |
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It is truncated by two planes perpendicular to its axis, |
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and one of its ends may come to a point. |
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It is given as two axis endpoints, and the starting |
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and ending radii: |
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.DS |
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mod cone id |
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0 |
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0 |
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8 |
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x0 y0 z0 |
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x1 y1 z1 |
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r0 r1 |
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.DE |
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.LP |
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.UL Cup |
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.PP |
236 |
greg |
1.4 |
A cup is an inverted cone (i.e., has an inward surface normal). |
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1.1 |
.LP |
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.UL Cylinder |
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.PP |
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A cylinder is like a cone, but its starting and ending radii are |
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equal. |
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.DS |
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mod cylinder id |
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0 |
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0 |
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7 |
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x0 y0 z0 |
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x1 y1 z1 |
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rad |
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.DE |
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.LP |
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.UL Tube |
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.PP |
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A tube is an inverted cylinder. |
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.LP |
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.UL Ring |
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.PP |
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A ring is a circular disk given by its center, surface |
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normal, and inner and outer radii: |
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.DS |
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mod ring id |
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0 |
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0 |
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8 |
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xcent ycent zcent |
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xdir ydir zdir |
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r0 r1 |
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.DE |
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.LP |
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.UL Mesh |
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.PP |
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A mesh is a compound surface, made up of many triangles and |
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an octree data structure to accelerate ray intersection. |
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It is typically converted from a Wavefront .OBJ file using the |
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greg |
1.4 |
.I obj2mesh |
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program. |
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greg |
1.1 |
.DS |
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mod mesh id |
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1+ meshfile transform |
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0 |
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0 |
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.DE |
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greg |
1.3 |
If the modifier is "void", then surfaces will use the modifiers given |
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in the original mesh description. |
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Otherwise, the modifier specified is used in their place. |
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greg |
1.1 |
The transform moves the mesh to the desired location in the scene. |
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Multiple instances using the same meshfile take little extra memory, |
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and the compiled mesh itself takes much less space than individual |
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polygons would. |
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In the case of an unsmoothed mesh, using the mesh primitive reduces |
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memory requirements by a factor of 30 relative to individual triangles. |
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If a mesh has smoothed surfaces, we save a factor of 50 or more, |
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permitting very detailed geometries that would otherwise exhaust the |
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available memory. |
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In addition, the mesh primitive can have associated (u,v) coordinates |
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for pattern and texture mapping. |
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greg |
1.4 |
These are made available to function files via the Lu and Lv variables. |
298 |
greg |
1.1 |
.LP |
299 |
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.UL Instance |
300 |
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.PP |
301 |
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An instance is a compound surface, given by the contents of an |
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octree file (created by oconv). |
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.DS |
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mod instance id |
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1+ octree transform |
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0 |
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0 |
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.DE |
309 |
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If the modifier is "void", then surfaces will use the modifiers given |
310 |
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in the original description. |
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Otherwise, the modifier specified is used in their place. |
312 |
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The transform moves the octree to the desired location in the scene. |
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Multiple instances using the same octree take little extra memory, |
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hence very complex descriptions can be rendered using this primitive. |
315 |
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.PP |
316 |
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There are a number of important limitations to be aware of when using |
317 |
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instances. |
318 |
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First, the scene description used to generate the octree must stand on |
319 |
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its own, without referring to modifiers in the parent description. |
320 |
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This is necessary for oconv to create the octree. |
321 |
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Second, light sources in the octree will not be incorporated correctly |
322 |
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in the calculation, and they are not recommended. |
323 |
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Finally, there is no advantage (other than convenience) to |
324 |
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using a single instance of an octree, or an octree containing only a |
325 |
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few surfaces. |
326 |
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An xform command on the subordinate description is prefered in such cases. |
327 |
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.NH 3 |
328 |
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Materials |
329 |
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.PP |
330 |
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A material defines the way light interacts with a surface. |
331 |
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The basic types are given below. |
332 |
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.LP |
333 |
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.UL Light |
334 |
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.PP |
335 |
greg |
1.4 |
Light is the basic material for self-luminous surfaces (i.e., light |
336 |
greg |
1.1 |
sources). |
337 |
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In addition to the source surface type, spheres, discs (rings with zero |
338 |
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inner radius), cylinders (provided they are long enough), and |
339 |
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polygons can act as light sources. |
340 |
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Polygons work best when they are rectangular. |
341 |
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Cones cannot be used at this time. |
342 |
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A pattern may be used to specify a light output distribution. |
343 |
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Light is defined simply as a RGB radiance value (watts/steradian/m2): |
344 |
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.DS |
345 |
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mod light id |
346 |
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0 |
347 |
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0 |
348 |
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3 red green blue |
349 |
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.DE |
350 |
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.LP |
351 |
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.UL Illum |
352 |
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.PP |
353 |
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Illum is used for secondary light sources with broad distributions. |
354 |
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A secondary light source is treated like any other |
355 |
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light source, except when viewed directly. |
356 |
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It then acts like it is made of a different material (indicated by |
357 |
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the string argument), or becomes invisible (if no string argument is given, |
358 |
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or the argument is "void"). |
359 |
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Secondary sources are useful when modeling windows or |
360 |
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brightly illuminated surfaces. |
361 |
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.DS |
362 |
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mod illum id |
363 |
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1 material |
364 |
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0 |
365 |
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3 red green blue |
366 |
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.DE |
367 |
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.LP |
368 |
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.UL Glow |
369 |
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.PP |
370 |
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Glow is used for surfaces that are self-luminous, but limited |
371 |
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in their effect. |
372 |
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In addition to the radiance value, a maximum radius for |
373 |
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shadow testing is given: |
374 |
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.DS |
375 |
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mod glow id |
376 |
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0 |
377 |
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0 |
378 |
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4 red green blue maxrad |
379 |
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.DE |
380 |
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If maxrad is zero, then the surface will never be tested |
381 |
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for shadow, although it may participate in an interreflection calculation. |
382 |
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If maxrad is negative, then the surface will never contribute to scene |
383 |
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illumination. |
384 |
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Glow sources will never illuminate objects on the other side of an |
385 |
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illum surface. |
386 |
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This provides a convenient way to illuminate local light fixture |
387 |
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geometry without overlighting nearby objects. |
388 |
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.LP |
389 |
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.UL Spotlight |
390 |
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.PP |
391 |
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Spotlight is used for self-luminous surfaces having directed output. |
392 |
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As well as radiance, the full cone angle (in degrees) |
393 |
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and orientation (output direction) vector are given. |
394 |
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The length of the orientation vector is the distance |
395 |
greg |
1.4 |
of the effective focus behind the source center (i.e., the focal length). |
396 |
greg |
1.1 |
.DS |
397 |
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mod spotlight id |
398 |
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|
0 |
399 |
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|
0 |
400 |
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7 red green blue angle xdir ydir zdir |
401 |
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.DE |
402 |
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.LP |
403 |
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.UL Mirror |
404 |
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.PP |
405 |
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Mirror is used for planar surfaces that produce secondary |
406 |
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source reflections. |
407 |
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|
This material should be used sparingly, as it may cause the light |
408 |
|
|
source calculation to blow up if it is applied to many small surfaces. |
409 |
|
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This material is only supported for flat surfaces such as polygons |
410 |
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and rings. |
411 |
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The arguments are simply the RGB reflectance values, which should be |
412 |
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between 0 and 1. |
413 |
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An optional string argument may be used like the illum type to specify a |
414 |
|
|
different material to be used for shading non-source rays. |
415 |
|
|
If this alternate material is given as "void", then the mirror surface |
416 |
|
|
will be invisible. |
417 |
|
|
This is only appropriate if the surface hides other (more detailed) |
418 |
|
|
geometry with the same overall reflectance. |
419 |
|
|
.DS |
420 |
|
|
mod mirror id |
421 |
|
|
1 material |
422 |
|
|
0 |
423 |
|
|
3 red green blue |
424 |
|
|
.DE |
425 |
|
|
.LP |
426 |
|
|
.UL Prism1 |
427 |
|
|
.PP |
428 |
|
|
The prism1 material is for general light redirection from prismatic |
429 |
|
|
glazings, generating secondary light sources. |
430 |
greg |
1.4 |
It can only be used to modify a planar surface (i.e., a polygon or disk) |
431 |
greg |
1.1 |
and should not result in either light concentration or scattering. |
432 |
|
|
The new direction of the ray can be on either side of the material, |
433 |
|
|
and the definitions must have the correct bidirectional properties |
434 |
|
|
to work properly with secondary light sources. |
435 |
|
|
The arguments give the coefficient for the redirected light |
436 |
|
|
and its direction. |
437 |
|
|
.DS |
438 |
|
|
mod prism1 id |
439 |
|
|
5+ coef dx dy dz funcfile transform |
440 |
|
|
0 |
441 |
|
|
n A1 A2 .. An |
442 |
|
|
.DE |
443 |
|
|
The new direction variables |
444 |
|
|
.I "dx, dy" |
445 |
|
|
and |
446 |
|
|
.I dz |
447 |
|
|
need not produce a normalized vector. |
448 |
|
|
For convenience, the variables |
449 |
|
|
.I "DxA, DyA" |
450 |
|
|
and |
451 |
|
|
.I DzA |
452 |
|
|
are defined as the normalized direction to the target light source. |
453 |
|
|
See section 2.2.1 on function files for further information. |
454 |
|
|
.LP |
455 |
|
|
.UL Prism2 |
456 |
|
|
.PP |
457 |
|
|
The material prism2 is identical to prism1 except that |
458 |
|
|
it provides for two ray redirections rather than one. |
459 |
|
|
.DS |
460 |
|
|
mod prism2 id |
461 |
|
|
9+ coef1 dx1 dy1 dz1 coef2 dx2 dy2 dz2 funcfile transform |
462 |
|
|
0 |
463 |
|
|
n A1 A2 .. An |
464 |
|
|
.DE |
465 |
|
|
.LP |
466 |
|
|
.UL Mist |
467 |
|
|
.PP |
468 |
|
|
Mist is a virtual material used to delineate a volume |
469 |
|
|
of participating atmosphere. |
470 |
|
|
A list of important light sources may be given, along with an |
471 |
|
|
extinction coefficient, scattering albedo and scattering eccentricity |
472 |
|
|
parameter. |
473 |
|
|
The light sources named by the string argument list |
474 |
|
|
will be tested for scattering within the volume. |
475 |
|
|
Sources are identified by name, and virtual light sources may be indicated |
476 |
|
|
by giving the relaying object followed by '>' followed by the source, i.e: |
477 |
|
|
.DS |
478 |
|
|
3 source1 mirror1>source10 mirror2>mirror1>source3 |
479 |
|
|
.DE |
480 |
|
|
Normally, only one source is given per mist material, and there is an |
481 |
|
|
upper limit of 32 to the total number of active scattering sources. |
482 |
|
|
The extinction coefficient, if given, is added to the global |
483 |
|
|
coefficient set on the command line. |
484 |
|
|
Extinction is in units of 1/distance (distance based on the world coordinates), |
485 |
|
|
and indicates the proportional loss of radiance over one unit distance. |
486 |
|
|
The scattering albedo, if present, will override the global setting within |
487 |
|
|
the volume. |
488 |
|
|
An albedo of 0\00\00 means a perfectly absorbing medium, and an albedo of |
489 |
|
|
1\01\01\0 means |
490 |
|
|
a perfectly scattering medium (no absorption). |
491 |
|
|
The scattering eccentricity parameter will likewise override the global |
492 |
|
|
setting if it is present. |
493 |
|
|
Scattering eccentricity indicates how much scattered light favors the |
494 |
|
|
forward direction, as fit by the Heyney-Greenstein function: |
495 |
|
|
.DS |
496 |
|
|
P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5 |
497 |
|
|
.DE |
498 |
|
|
A perfectly isotropic scattering medium has a g parameter of 0, and |
499 |
|
|
a highly directional material has a g parameter close to 1. |
500 |
|
|
Fits to the g parameter may be found along with typical extinction |
501 |
|
|
coefficients and scattering albedos for various atmospheres and |
502 |
|
|
cloud types in USGS meteorological tables. |
503 |
|
|
(A pattern will be applied to the extinction values.)\0 |
504 |
|
|
.DS |
505 |
|
|
mod mist id |
506 |
|
|
N src1 src2 .. srcN |
507 |
|
|
0 |
508 |
|
|
0|3|6|7 [ rext gext bext [ ralb galb balb [ g ] ] ] |
509 |
|
|
.DE |
510 |
|
|
There are two usual uses of the mist type. |
511 |
|
|
One is to surround a beam from a spotlight or laser so that it is |
512 |
|
|
visible during rendering. |
513 |
|
|
For this application, it is important to use a cone (or cylinder) that |
514 |
|
|
is long enough and wide enough to contain the important visible portion. |
515 |
|
|
Light source photometry and intervening objects will have the desired |
516 |
|
|
effect, and crossing beams will result in additive scattering. |
517 |
|
|
For this application, it is best to leave off the real arguments, and |
518 |
|
|
use the global rendering parameters to control the atmosphere. |
519 |
|
|
The second application is to model clouds or other localized media. |
520 |
|
|
Complex boundary geometry may be used to give shape to a uniform medium, |
521 |
|
|
so long as the boundary encloses a proper volume. |
522 |
|
|
Alternatively, a pattern may be used to set the line integral value |
523 |
|
|
through the cloud for a ray entering or exiting a point in a given |
524 |
|
|
direction. |
525 |
|
|
For this application, it is best if cloud volumes do not overlap each other, |
526 |
|
|
and opaque objects contained within them may not be illuminated correctly |
527 |
|
|
unless the line integrals consider enclosed geometry. |
528 |
|
|
.LP |
529 |
|
|
.UL Plastic |
530 |
|
|
.PP |
531 |
|
|
Plastic is a material with uncolored highlights. |
532 |
|
|
It is given by its RGB reflectance, its fraction of specularity, |
533 |
|
|
and its roughness value. |
534 |
|
|
Roughness is specified as the rms slope of surface facets. |
535 |
|
|
A value of 0 corresponds to a perfectly smooth surface, and |
536 |
|
|
a value of 1 would be a very rough surface. |
537 |
|
|
Specularity fractions greater than 0.1 and |
538 |
|
|
roughness values greater than 0.2 are not very |
539 |
|
|
realistic. |
540 |
|
|
(A pattern modifying plastic will affect the material color.) |
541 |
|
|
.DS |
542 |
|
|
mod plastic id |
543 |
|
|
0 |
544 |
|
|
0 |
545 |
|
|
5 red green blue spec rough |
546 |
|
|
.DE |
547 |
|
|
.LP |
548 |
|
|
.UL Metal |
549 |
|
|
.PP |
550 |
|
|
Metal is similar to plastic, but specular highlights |
551 |
|
|
are modified by the material color. |
552 |
|
|
Specularity of metals is usually .9 or greater. |
553 |
|
|
As for plastic, roughness values above .2 are uncommon. |
554 |
|
|
.LP |
555 |
|
|
.UL Trans |
556 |
|
|
.PP |
557 |
|
|
Trans is a translucent material, similar to plastic. |
558 |
|
|
The transmissivity is the fraction of penetrating light that |
559 |
|
|
travels all the way through the material. |
560 |
|
|
The transmitted specular component is the fraction of transmitted |
561 |
|
|
light that is not diffusely scattered. |
562 |
|
|
Transmitted and diffusely reflected light is modified by the material color. |
563 |
|
|
Translucent objects are infinitely thin. |
564 |
|
|
.DS |
565 |
|
|
mod trans id |
566 |
|
|
0 |
567 |
|
|
0 |
568 |
|
|
7 red green blue spec rough trans tspec |
569 |
|
|
.DE |
570 |
|
|
.LP |
571 |
|
|
.UL Plastic2 |
572 |
|
|
.PP |
573 |
|
|
Plastic2 is similar to plastic, but with anisotropic |
574 |
|
|
roughness. |
575 |
|
|
This means that highlights in the surface will appear elliptical rather |
576 |
|
|
than round. |
577 |
|
|
The orientation of the anisotropy is determined by the unnormalized |
578 |
|
|
direction vector |
579 |
|
|
.I "ux uy uz". |
580 |
|
|
These three expressions (separated by white space) are evaluated in |
581 |
|
|
the context of the function file |
582 |
|
|
.I funcfile. |
583 |
greg |
1.4 |
If no function file is required (i.e., no special variables or |
584 |
greg |
1.1 |
functions are required), a period (`.') may be given in its |
585 |
|
|
place. |
586 |
|
|
(See the discussion of Function Files in the Auxiliary Files section). |
587 |
|
|
The |
588 |
|
|
.I urough |
589 |
|
|
value defines the roughness along the |
590 |
|
|
.B u |
591 |
|
|
vector given projected onto the surface. |
592 |
|
|
The |
593 |
|
|
.I vrough |
594 |
|
|
value defines the roughness perpendicular to this vector. |
595 |
|
|
Note that the highlight will be narrower in the direction of the |
596 |
|
|
smaller roughness value. |
597 |
|
|
Roughness values of zero are not allowed for efficiency reasons |
598 |
|
|
since the behavior would be the same as regular plastic in that |
599 |
|
|
case. |
600 |
|
|
.DS |
601 |
|
|
mod plastic2 id |
602 |
|
|
4+ ux uy uz funcfile transform |
603 |
|
|
0 |
604 |
|
|
6 red green blue spec urough vrough |
605 |
|
|
.DE |
606 |
|
|
.LP |
607 |
|
|
.UL Metal2 |
608 |
|
|
.PP |
609 |
|
|
Metal2 is the same as plastic2, except that the highlights are |
610 |
|
|
modified by the material color. |
611 |
|
|
.LP |
612 |
|
|
.UL Trans2 |
613 |
|
|
.PP |
614 |
|
|
Trans2 is the anisotropic version of trans. |
615 |
|
|
The string arguments are the same as for plastic2, and the real |
616 |
|
|
arguments are the same as for trans but with an additional roughness |
617 |
|
|
value. |
618 |
|
|
.DS |
619 |
|
|
mod trans2 id |
620 |
|
|
4+ ux uy uz funcfile transform |
621 |
|
|
0 |
622 |
|
|
8 red green blue spec urough vrough trans tspec |
623 |
|
|
.DE |
624 |
|
|
.LP |
625 |
|
|
.UL Dielectric |
626 |
|
|
.PP |
627 |
|
|
A dielectric material is transparent, and it refracts light |
628 |
|
|
as well as reflecting it. |
629 |
|
|
Its behavior is determined by the index of refraction and |
630 |
|
|
transmission coefficient in each wavelength band per unit length. |
631 |
|
|
Common glass has a index of refraction (n) around 1.5, |
632 |
|
|
and a transmission coefficient of roughly 0.92 over an inch. |
633 |
|
|
An additional number, the Hartmann constant, describes how |
634 |
|
|
the index of refraction changes as a function of wavelength. |
635 |
|
|
It is usually zero. |
636 |
|
|
(A pattern modifies only the refracted value.) |
637 |
|
|
.DS |
638 |
|
|
mod dielectric id |
639 |
|
|
0 |
640 |
|
|
0 |
641 |
|
|
5 rtn gtn btn n hc |
642 |
|
|
.DE |
643 |
|
|
.LP |
644 |
|
|
.UL Interface |
645 |
|
|
.PP |
646 |
|
|
An interface is a boundary between two dielectrics. |
647 |
|
|
The first transmission coefficient and refractive index are for the inside; |
648 |
|
|
the second ones are for the outside. |
649 |
|
|
Ordinary dielectrics are surrounded by a vacuum (1 1 1 1). |
650 |
|
|
.DS |
651 |
|
|
mod interface id |
652 |
|
|
0 |
653 |
|
|
0 |
654 |
|
|
8 rtn1 gtn1 btn1 n1 rtn2 gtn2 btn2 n2 |
655 |
|
|
.DE |
656 |
|
|
.LP |
657 |
|
|
.UL Glass |
658 |
|
|
.PP |
659 |
|
|
Glass is similar to dielectric, but it is optimized for thin glass |
660 |
|
|
surfaces (n = 1.52). |
661 |
|
|
One transmitted ray and one reflected ray is produced. |
662 |
|
|
By using a single surface is in place of two, internal reflections |
663 |
|
|
are avoided. |
664 |
|
|
The surface orientation is irrelevant, as it is for plastic, |
665 |
|
|
metal, and trans. |
666 |
|
|
The only specification required is the transmissivity at normal |
667 |
|
|
incidence. |
668 |
|
|
(Transmissivity is the amount of light not absorbed in one traversal |
669 |
|
|
of the material. |
670 |
|
|
Transmittance -- the value usually measured -- is the total light |
671 |
|
|
transmitted through the pane including multiple reflections.)\0 |
672 |
|
|
To compute transmissivity (tn) from transmittance (Tn) use: |
673 |
|
|
.DS |
674 |
|
|
tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn |
675 |
|
|
.DE |
676 |
|
|
Standard 88% transmittance glass has a transmissivity of 0.96. |
677 |
|
|
(A pattern modifying glass will affect the transmissivity.) |
678 |
|
|
If a fourth real argument is given, it is interpreted as the index of |
679 |
|
|
refraction to use instead of 1.52. |
680 |
|
|
.DS |
681 |
|
|
mod glass id |
682 |
|
|
0 |
683 |
|
|
0 |
684 |
|
|
3 rtn gtn btn |
685 |
|
|
.DE |
686 |
|
|
.LP |
687 |
|
|
.UL Plasfunc |
688 |
|
|
.PP |
689 |
|
|
Plasfunc in used for the procedural definition of plastic-like |
690 |
|
|
materials with arbitrary bidirectional reflectance distribution |
691 |
|
|
functions (BRDF's). |
692 |
|
|
The arguments to this material include the color and specularity, |
693 |
|
|
as well as the function defining the specular distribution and the |
694 |
|
|
auxiliary file where it may be found. |
695 |
|
|
.DS |
696 |
|
|
mod plasfunc id |
697 |
|
|
2+ refl funcfile transform |
698 |
|
|
0 |
699 |
|
|
4+ red green blue spec A5 .. |
700 |
|
|
.DE |
701 |
|
|
The function |
702 |
|
|
.I refl |
703 |
|
|
takes four arguments, the x, y and z |
704 |
|
|
direction towards the incident light, and the solid angle |
705 |
|
|
subtended by the source. |
706 |
|
|
The solid angle is provided to facilitate averaging, and is usually |
707 |
|
|
ignored. |
708 |
|
|
The |
709 |
|
|
.I refl |
710 |
|
|
function should integrate to 1 over |
711 |
|
|
the projected hemisphere to maintain energy balance. |
712 |
|
|
At least four real arguments must be given, and these are made |
713 |
|
|
available along with any additional values to the reflectance |
714 |
|
|
function. |
715 |
|
|
Currently, only the contribution from direct light sources is |
716 |
|
|
considered in the specular calculation. |
717 |
|
|
As in most material types, the surface normal is always |
718 |
|
|
altered to face the incoming ray. |
719 |
|
|
.LP |
720 |
|
|
.UL Metfunc |
721 |
|
|
.PP |
722 |
|
|
Metfunc is identical to plasfunc and takes the same arguments, but |
723 |
|
|
the specular component is multiplied also by the material color. |
724 |
|
|
.LP |
725 |
|
|
.UL Transfunc |
726 |
|
|
.PP |
727 |
|
|
Transfunc is similar to plasfunc but with an arbitrary bidirectional |
728 |
|
|
transmittance distribution as well as a reflectance distribution. |
729 |
|
|
Both reflectance and transmittance are specified with the same function. |
730 |
|
|
.DS |
731 |
|
|
mod transfunc id |
732 |
|
|
2+ brtd funcfile transform |
733 |
|
|
0 |
734 |
|
|
6+ red green blue rspec trans tspec A7 .. |
735 |
|
|
.DE |
736 |
|
|
Where |
737 |
|
|
.I trans |
738 |
|
|
is the total light transmitted and |
739 |
|
|
.I tspec |
740 |
|
|
is the non-Lambertian fraction of transmitted light. |
741 |
|
|
The function |
742 |
|
|
.I brtd |
743 |
|
|
should integrate to 1 over each projected hemisphere. |
744 |
|
|
.LP |
745 |
|
|
.UL BRTDfunc |
746 |
|
|
.PP |
747 |
|
|
The material BRTDfunc gives the maximum flexibility over surface |
748 |
|
|
reflectance and transmittance, providing for spectrally-dependent |
749 |
|
|
specular rays and reflectance and transmittance distribution functions. |
750 |
|
|
.DS |
751 |
|
|
mod BRTDfunc id |
752 |
|
|
10+ rrefl grefl brefl |
753 |
|
|
rtrns gtrns btrns |
754 |
|
|
rbrtd gbrtd bbrtd |
755 |
|
|
funcfile transform |
756 |
|
|
0 |
757 |
|
|
9+ rfdif gfdif bfdif |
758 |
|
|
rbdif gbdif bbdif |
759 |
|
|
rtdif gtdif btdif |
760 |
|
|
A10 .. |
761 |
|
|
.DE |
762 |
|
|
The variables |
763 |
|
|
.I "rrefl, grefl" |
764 |
|
|
and |
765 |
|
|
.I brefl |
766 |
|
|
specify the color coefficients for |
767 |
|
|
the ideal specular (mirror) reflection of the surface. |
768 |
|
|
The variables |
769 |
|
|
.I "rtrns, gtrns" |
770 |
|
|
and |
771 |
|
|
.I btrns |
772 |
|
|
specify the color coefficients for the ideal specular transmission. |
773 |
|
|
The functions |
774 |
|
|
.I "rbrtd, gbrtd" |
775 |
|
|
and |
776 |
|
|
.I bbrtd |
777 |
|
|
take the direction to the incident light (and its solid angle) |
778 |
|
|
and compute the color coefficients for the directional diffuse part of |
779 |
|
|
reflection and transmission. |
780 |
|
|
As a special case, three identical values of '0' may be given in place of |
781 |
|
|
these function names to indicate no directional diffuse component. |
782 |
|
|
.PP |
783 |
|
|
Unlike most other material types, the surface normal is not altered to |
784 |
|
|
face the incoming ray. |
785 |
|
|
Thus, functions and variables must pay attention to the orientation of |
786 |
|
|
the surface and make adjustments appropriately. |
787 |
|
|
However, the special variables for the perturbed dot product and surface |
788 |
|
|
normal, |
789 |
|
|
.I "RdotP, NxP, NyP" |
790 |
|
|
and |
791 |
|
|
.I NzP |
792 |
|
|
are reoriented as if the ray hit the front surface for convenience. |
793 |
|
|
.PP |
794 |
|
|
A diffuse reflection component may be given for the front side with |
795 |
|
|
.I "rfdif, gfdif" |
796 |
|
|
and |
797 |
|
|
.I bfdif |
798 |
|
|
for the front side of the surface or |
799 |
|
|
.I "rbdif, gbdif" |
800 |
|
|
and |
801 |
|
|
.I bbdif |
802 |
|
|
for the back side. |
803 |
|
|
The diffuse transmittance (must be the same for both sides by physical law) |
804 |
|
|
is given by |
805 |
|
|
.I "rtdif, gtdif" |
806 |
|
|
and |
807 |
|
|
.I btdif. |
808 |
|
|
A pattern will modify these diffuse scattering values, |
809 |
|
|
and will be available through the special variables |
810 |
|
|
.I "CrP, CgP" |
811 |
|
|
and |
812 |
|
|
.I CbP. |
813 |
|
|
.PP |
814 |
|
|
Care must be taken when using this material type to produce a physically |
815 |
|
|
valid reflection model. |
816 |
|
|
The reflectance functions should be bidirectional, and under no circumstances |
817 |
|
|
should the sum of reflected diffuse, transmitted diffuse, reflected specular, |
818 |
|
|
transmitted specular and the integrated directional diffuse component be |
819 |
|
|
greater than one. |
820 |
|
|
.LP |
821 |
|
|
.UL Plasdata |
822 |
|
|
.PP |
823 |
|
|
Plasdata is used for arbitrary BRDF's that are most conveniently |
824 |
|
|
given as interpolated data. |
825 |
|
|
The arguments to this material are the data file and coordinate index |
826 |
|
|
functions, as well as a function to optionally modify the data |
827 |
|
|
values. |
828 |
|
|
.DS |
829 |
|
|
mod plasdata id |
830 |
|
|
3+n+ |
831 |
|
|
func datafile |
832 |
|
|
funcfile x1 x2 .. xn transform |
833 |
|
|
0 |
834 |
|
|
4+ red green blue spec A5 .. |
835 |
|
|
.DE |
836 |
|
|
The coordinate indices |
837 |
|
|
.I "(x1, x2," |
838 |
|
|
etc.) are themselves functions of |
839 |
|
|
the x, y and z direction to the incident light, plus the solid angle |
840 |
|
|
subtended by the light source (usually ignored). |
841 |
|
|
The data function |
842 |
|
|
.I (func) |
843 |
|
|
takes five variables, the |
844 |
|
|
interpolated value from the n-dimensional data file, followed by the |
845 |
|
|
x, y and z direction to the incident light and the solid angle of the source. |
846 |
|
|
The light source direction and size may of course be ignored by the function. |
847 |
|
|
.LP |
848 |
|
|
.UL Metdata |
849 |
|
|
.PP |
850 |
|
|
As metfunc is to plasfunc, metdata is to plasdata. |
851 |
|
|
Metdata takes the same arguments as plasdata, but the specular |
852 |
|
|
component is modified by the given material color. |
853 |
|
|
.LP |
854 |
|
|
.UL Transdata |
855 |
|
|
.PP |
856 |
|
|
Transdata is like plasdata but the specification includes transmittance |
857 |
|
|
as well as reflectance. |
858 |
|
|
The parameters are as follows. |
859 |
|
|
.DS |
860 |
|
|
mod transdata id |
861 |
|
|
3+n+ |
862 |
|
|
func datafile |
863 |
|
|
funcfile x1 x2 .. xn transform |
864 |
|
|
0 |
865 |
|
|
6+ red green blue rspec trans tspec A7 .. |
866 |
|
|
.DE |
867 |
|
|
.LP |
868 |
|
|
.UL Antimatter |
869 |
|
|
.PP |
870 |
|
|
Antimatter is a material that can "subtract" volumes from other volumes. |
871 |
|
|
A ray passing into an antimatter object becomes blind to all the specified |
872 |
|
|
modifiers: |
873 |
|
|
.DS |
874 |
|
|
mod antimatter id |
875 |
|
|
N mod1 mod2 .. modN |
876 |
|
|
0 |
877 |
|
|
0 |
878 |
|
|
.DE |
879 |
|
|
The first modifier will also be used to shade the area leaving the |
880 |
|
|
antimatter volume and entering the regular volume. |
881 |
|
|
If mod1 is void, the antimatter volume is completely invisible. |
882 |
|
|
Antimatter does not work properly with the material type "trans", |
883 |
|
|
and multiple antimatter surfaces should be disjoint. |
884 |
|
|
The viewpoint must be outside all volumes concerned for a correct |
885 |
|
|
rendering. |
886 |
|
|
.NH 3 |
887 |
|
|
Textures |
888 |
|
|
.PP |
889 |
|
|
A texture is a perturbation of the surface normal, and |
890 |
|
|
is given by either a function or data. |
891 |
|
|
.LP |
892 |
|
|
.UL Texfunc |
893 |
|
|
.PP |
894 |
|
|
A texfunc uses an auxiliary function file |
895 |
|
|
to specify a procedural texture: |
896 |
|
|
.DS |
897 |
|
|
mod texfunc id |
898 |
|
|
4+ xpert ypert zpert funcfile transform |
899 |
|
|
0 |
900 |
|
|
n A1 A2 .. An |
901 |
|
|
.DE |
902 |
|
|
.LP |
903 |
|
|
.UL Texdata |
904 |
|
|
.PP |
905 |
|
|
A texdata texture uses three data files to get the surface |
906 |
|
|
normal perturbations. |
907 |
|
|
The variables |
908 |
|
|
.I xfunc, |
909 |
|
|
.I yfunc |
910 |
|
|
and |
911 |
|
|
.I zfunc |
912 |
|
|
take three arguments |
913 |
|
|
each from the interpolated values in |
914 |
|
|
.I xdfname, |
915 |
|
|
.I ydfname |
916 |
|
|
and |
917 |
|
|
.I zdfname. |
918 |
|
|
.DS |
919 |
|
|
mod texdata id |
920 |
|
|
8+ xfunc yfunc zfunc xdfname ydfname zdfname vfname x0 x1 .. xf |
921 |
|
|
0 |
922 |
|
|
n A1 A2 .. An |
923 |
|
|
.DE |
924 |
|
|
.NH 3 |
925 |
|
|
Patterns |
926 |
|
|
.PP |
927 |
|
|
Patterns are used to modify the reflectance of materials. |
928 |
|
|
The basic types are given below. |
929 |
|
|
.LP |
930 |
|
|
.UL Colorfunc |
931 |
|
|
.PP |
932 |
|
|
A colorfunc is a procedurally defined color pattern. |
933 |
|
|
It is specified as follows: |
934 |
|
|
.DS |
935 |
|
|
mod colorfunc id |
936 |
|
|
4+ red green blue funcfile transform |
937 |
|
|
0 |
938 |
|
|
n A1 A2 .. An |
939 |
|
|
.DE |
940 |
|
|
.LP |
941 |
|
|
.UL Brightfunc |
942 |
|
|
.PP |
943 |
|
|
A brightfunc is the same as a colorfunc, except it is monochromatic. |
944 |
|
|
.DS |
945 |
|
|
mod brightfunc id |
946 |
|
|
2+ refl funcfile transform |
947 |
|
|
0 |
948 |
|
|
n A1 A2 .. An |
949 |
|
|
.DE |
950 |
|
|
.LP |
951 |
|
|
.UL Colordata |
952 |
|
|
.PP |
953 |
|
|
Colordata uses an interpolated data map to modify a material's color. |
954 |
|
|
The map is n-dimensional, and is stored in three |
955 |
|
|
auxiliary files, one for each color. |
956 |
|
|
The coordinates used to look up and interpolate the data are |
957 |
|
|
defined in another auxiliary file. |
958 |
|
|
The interpolated data values are modified by functions of |
959 |
|
|
one or three variables. |
960 |
|
|
If the functions are of one variable, then they are passed the |
961 |
|
|
corresponding color component (red or green or blue). |
962 |
|
|
If the functions are of three variables, then they are passed the |
963 |
|
|
original red, green, and blue values as parameters. |
964 |
|
|
.DS |
965 |
|
|
mod colordata id |
966 |
|
|
7+n+ |
967 |
|
|
rfunc gfunc bfunc rdatafile gdatafile bdatafile |
968 |
|
|
funcfile x1 x2 .. xn transform |
969 |
|
|
0 |
970 |
|
|
m A1 A2 .. Am |
971 |
|
|
.DE |
972 |
|
|
.LP |
973 |
|
|
.UL Brightdata |
974 |
|
|
.PP |
975 |
|
|
Brightdata is like colordata, except monochromatic. |
976 |
|
|
.DS |
977 |
|
|
mod brightdata id |
978 |
|
|
3+n+ |
979 |
|
|
func datafile |
980 |
|
|
funcfile x1 x2 .. xn transform |
981 |
|
|
0 |
982 |
|
|
m A1 A2 .. Am |
983 |
|
|
.DE |
984 |
|
|
.LP |
985 |
|
|
.UL Colorpict |
986 |
|
|
.PP |
987 |
|
|
Colorpict is a special case of colordata, where the pattern is |
988 |
|
|
a two-dimensional image stored in the RADIANCE picture format. |
989 |
|
|
The dimensions of the image data are determined by the picture |
990 |
|
|
such that the smaller dimension is always 1, and the other |
991 |
|
|
is the ratio between the larger and the smaller. |
992 |
|
|
For example, a 500x338 picture would have coordinates (u,v) |
993 |
|
|
in the rectangle between (0,0) and (1.48,1). |
994 |
|
|
.DS |
995 |
|
|
mod colorpict id |
996 |
|
|
7+ |
997 |
|
|
rfunc gfunc bfunc pictfile |
998 |
|
|
funcfile u v transform |
999 |
|
|
0 |
1000 |
|
|
m A1 A2 .. Am |
1001 |
|
|
.DE |
1002 |
|
|
.LP |
1003 |
|
|
.UL Colortext |
1004 |
|
|
.PP |
1005 |
|
|
Colortext is dichromatic writing in a polygonal font. |
1006 |
|
|
The font is defined in an auxiliary file, such as |
1007 |
|
|
.I helvet.fnt. |
1008 |
|
|
The text itself is also specified in a separate file, or |
1009 |
|
|
can be part of the material arguments. |
1010 |
|
|
The character size, orientation, aspect ratio and slant is |
1011 |
|
|
determined by right and down motion vectors. |
1012 |
|
|
The upper left origin for the text block as well as |
1013 |
|
|
the foreground and background colors |
1014 |
|
|
must also be given. |
1015 |
|
|
.DS |
1016 |
|
|
mod colortext id |
1017 |
|
|
2 fontfile textfile |
1018 |
|
|
0 |
1019 |
|
|
15+ |
1020 |
|
|
Ox Oy Oz |
1021 |
|
|
Rx Ry Rz |
1022 |
|
|
Dx Dy Dz |
1023 |
|
|
rfore gfore bfore |
1024 |
|
|
rback gback bback |
1025 |
|
|
[spacing] |
1026 |
|
|
.DE |
1027 |
|
|
or: |
1028 |
|
|
.DS |
1029 |
|
|
mod colortext id |
1030 |
|
|
2+N fontfile . This is a line with N words ... |
1031 |
|
|
0 |
1032 |
|
|
15+ |
1033 |
|
|
Ox Oy Oz |
1034 |
|
|
Rx Ry Rz |
1035 |
|
|
Dx Dy Dz |
1036 |
|
|
rfore gfore bfore |
1037 |
|
|
rback gback bback |
1038 |
|
|
[spacing] |
1039 |
|
|
.DE |
1040 |
|
|
.LP |
1041 |
|
|
.UL Brighttext |
1042 |
|
|
.PP |
1043 |
|
|
Brighttext is like colortext, but the writing is monochromatic. |
1044 |
|
|
.DS |
1045 |
|
|
mod brighttext id |
1046 |
|
|
2 fontfile textfile |
1047 |
|
|
0 |
1048 |
|
|
11+ |
1049 |
|
|
Ox Oy Oz |
1050 |
|
|
Rx Ry Rz |
1051 |
|
|
Dx Dy Dz |
1052 |
|
|
foreground background |
1053 |
|
|
[spacing] |
1054 |
|
|
.DE |
1055 |
|
|
or: |
1056 |
|
|
.DS |
1057 |
|
|
mod brighttext id |
1058 |
|
|
2+N fontfile . This is a line with N words ... |
1059 |
|
|
0 |
1060 |
|
|
11+ |
1061 |
|
|
Ox Oy Oz |
1062 |
|
|
Rx Ry Rz |
1063 |
|
|
Dx Dy Dz |
1064 |
|
|
foreground background |
1065 |
|
|
[spacing] |
1066 |
|
|
.DE |
1067 |
|
|
.LP |
1068 |
|
|
By default, a uniform spacing algorithm is used that guarantees |
1069 |
|
|
every character will appear in a precisely determined position. |
1070 |
|
|
Unfortunately, such a scheme results in rather unattractive and difficult to |
1071 |
|
|
read text with most fonts. |
1072 |
|
|
The optional |
1073 |
|
|
.I spacing |
1074 |
|
|
value defines the distance between characters for proportional spacing. |
1075 |
|
|
A positive value selects a spacing algorithm that preserves right margins and |
1076 |
|
|
indentation, but does not provide the ultimate in proportionally spaced text. |
1077 |
|
|
A negative value insures that characters are properly spaced, but the |
1078 |
|
|
placement of words then varies unpredictably. |
1079 |
|
|
The choice depends on the relative importance of spacing versus formatting. |
1080 |
|
|
When presenting a section of formatted text, a positive spacing value is |
1081 |
|
|
usually preferred. |
1082 |
|
|
A single line of text will often be accompanied by a negative spacing value. |
1083 |
|
|
A section of text meant to depict a picture, perhaps using a special purpose |
1084 |
|
|
font such as hexbit4x1.fnt, calls for uniform spacing. |
1085 |
|
|
Reasonable magnitudes for proportional spacing are |
1086 |
|
|
between 0.1 (for tightly spaced characters) and 0.3 (for wide spacing). |
1087 |
|
|
.NH 3 |
1088 |
|
|
Mixtures |
1089 |
|
|
.PP |
1090 |
|
|
A mixture is a blend of one or more materials or textures and patterns. |
1091 |
|
|
The basic types are given below. |
1092 |
|
|
.LP |
1093 |
|
|
.UL Mixfunc |
1094 |
|
|
.PP |
1095 |
|
|
A mixfunc mixes two modifiers procedurally. |
1096 |
|
|
It is specified as follows: |
1097 |
|
|
.DS |
1098 |
|
|
mod mixfunc id |
1099 |
|
|
4+ foreground background vname funcfile transform |
1100 |
|
|
0 |
1101 |
|
|
n A1 A2 .. An |
1102 |
|
|
.DE |
1103 |
|
|
Foreground and background are modifier names that must be |
1104 |
|
|
defined earlier in the scene description. |
1105 |
|
|
If one of these is a material, then |
1106 |
|
|
the modifier of the mixfunc must be "void". |
1107 |
|
|
(Either the foreground or background modifier may be "void", |
1108 |
|
|
which serves as a form of opacity control when used with a material.)\0 |
1109 |
|
|
Vname is the coefficient defined in funcfile that determines the influence |
1110 |
|
|
of foreground. |
1111 |
|
|
The background coefficient is always (1-vname). |
1112 |
|
|
Since the references are not resolved until runtime, the last |
1113 |
|
|
definitions of the modifier id's will be used. |
1114 |
|
|
This can result in modifier loops, which are detected by the |
1115 |
|
|
renderer. |
1116 |
|
|
.LP |
1117 |
|
|
.UL Mixdata |
1118 |
|
|
.PP |
1119 |
|
|
Mixdata combines two modifiers using an auxiliary data file: |
1120 |
|
|
.DS |
1121 |
|
|
mod mixdata id |
1122 |
|
|
5+n+ |
1123 |
|
|
foreground background func datafile |
1124 |
|
|
funcfile x1 x2 .. xn transform |
1125 |
|
|
0 |
1126 |
|
|
m A1 A2 .. Am |
1127 |
|
|
.DE |
1128 |
|
|
.LP |
1129 |
|
|
.UL Mixpict |
1130 |
|
|
.PP |
1131 |
|
|
Mixpict combines two modifiers based on a picture: |
1132 |
|
|
.DS |
1133 |
|
|
mod mixpict id |
1134 |
|
|
7+ |
1135 |
|
|
foreground background func pictfile |
1136 |
|
|
funcfile u v transform |
1137 |
|
|
0 |
1138 |
|
|
m A1 A2 .. Am |
1139 |
|
|
.DE |
1140 |
|
|
The mixing coefficient function "func" takes three |
1141 |
|
|
arguments, the red, green and blue values |
1142 |
|
|
corresponding to the pixel at (u,v). |
1143 |
|
|
.LP |
1144 |
|
|
.UL Mixtext |
1145 |
|
|
.PP |
1146 |
|
|
Mixtext uses one modifier for the text foreground, and one for the |
1147 |
|
|
background: |
1148 |
|
|
.DS |
1149 |
|
|
mod mixtext id |
1150 |
|
|
4 foreground background fontfile textfile |
1151 |
|
|
0 |
1152 |
|
|
9+ |
1153 |
|
|
Ox Oy Oz |
1154 |
|
|
Rx Ry Rz |
1155 |
|
|
Dx Dy Dz |
1156 |
|
|
[spacing] |
1157 |
|
|
.DE |
1158 |
|
|
or: |
1159 |
|
|
.DS |
1160 |
|
|
mod mixtext id |
1161 |
|
|
4+N |
1162 |
|
|
foreground background fontfile . |
1163 |
|
|
This is a line with N words ... |
1164 |
|
|
0 |
1165 |
|
|
9+ |
1166 |
|
|
Ox Oy Oz |
1167 |
|
|
Rx Ry Rz |
1168 |
|
|
Dx Dy Dz |
1169 |
|
|
[spacing] |
1170 |
|
|
.DE |
1171 |
|
|
.NH 2 |
1172 |
|
|
Auxiliary Files |
1173 |
|
|
.PP |
1174 |
|
|
Auxiliary files used in textures and patterns |
1175 |
|
|
are accessed by the programs during image generation. |
1176 |
|
|
These files may be located in the working directory, or in |
1177 |
|
|
a library directory. |
1178 |
|
|
The environment variable |
1179 |
|
|
.I RAYPATH |
1180 |
|
|
can be assigned an alternate set of search directories. |
1181 |
|
|
Following is a brief description of some common file types. |
1182 |
|
|
.NH 3 |
1183 |
|
|
Function Files |
1184 |
|
|
.PP |
1185 |
|
|
A function file contains the definitions of variables, functions |
1186 |
|
|
and constants used by a primitive. |
1187 |
|
|
The transformation that accompanies the file name contains the necessary |
1188 |
|
|
rotations, translations and scalings to bring the coordinates of |
1189 |
|
|
the function file into agreement with the world coordinates. |
1190 |
|
|
The transformation specification is the same as for the |
1191 |
|
|
.I xform |
1192 |
|
|
command. |
1193 |
|
|
An example function file is given below: |
1194 |
|
|
.DS |
1195 |
|
|
{ |
1196 |
|
|
This is a comment, enclosed in curly braces. |
1197 |
|
|
{Comments can be nested.} |
1198 |
|
|
} |
1199 |
|
|
{ standard expressions use +,-,*,/,^,(,) } |
1200 |
|
|
vname = Ny * func(A1) ; |
1201 |
|
|
{ constants are defined with a colon } |
1202 |
|
|
const : sqrt(PI/2) ; |
1203 |
|
|
{ user-defined functions add to library } |
1204 |
|
|
func(x) = 5 + A1*sin(x/3) ; |
1205 |
|
|
{ functions may be passed and recursive } |
1206 |
|
|
rfunc(f,x) = if(x,f(x),f(-x)*rfunc(f,x+1)) ; |
1207 |
|
|
{ constant functions may also be defined } |
1208 |
|
|
cfunc(x) : 10*x / sqrt(x) ; |
1209 |
|
|
.DE |
1210 |
|
|
Many variables and functions are already defined by the program, |
1211 |
|
|
and they are listed in the file |
1212 |
|
|
.I rayinit.cal. |
1213 |
|
|
The following variables are particularly important: |
1214 |
|
|
.DS |
1215 |
|
|
Dx, Dy, Dz - incident ray direction |
1216 |
greg |
1.4 |
Nx, Ny, Nz - surface normal at intersection point |
1217 |
greg |
1.1 |
Px, Py, Pz - intersection point |
1218 |
greg |
1.4 |
T - distance from start |
1219 |
|
|
Ts - single ray (shadow) distance |
1220 |
greg |
1.1 |
Rdot - cosine between ray and normal |
1221 |
|
|
arg(0) - number of real arguments |
1222 |
|
|
arg(i) - i'th real argument |
1223 |
|
|
.DE |
1224 |
greg |
1.4 |
For mesh objects, the local surface coordinates are available: |
1225 |
|
|
.DS |
1226 |
|
|
Lu, Lv - local (u,v) coordinates |
1227 |
|
|
.DE |
1228 |
greg |
1.1 |
For BRDF types, the following variables are defined as well: |
1229 |
|
|
.DS |
1230 |
|
|
NxP, NyP, NzP - perturbed surface normal |
1231 |
|
|
RdotP - perturbed dot product |
1232 |
|
|
CrP, CgP, CbP - perturbed material color |
1233 |
|
|
.DE |
1234 |
|
|
A unique context is set up for each file so that the same variable |
1235 |
|
|
may appear in different function files without conflict. |
1236 |
|
|
The variables listed above and any others defined in |
1237 |
|
|
rayinit.cal are available globally. |
1238 |
|
|
If no file is needed by a given primitive because all the required |
1239 |
|
|
variables are global, a period (`.') can be given in |
1240 |
|
|
place of the file name. |
1241 |
|
|
It is also possible to give an expression instead of a straight |
1242 |
|
|
variable name in a scene file, although such expressions should |
1243 |
greg |
1.4 |
be kept simple if possible. |
1244 |
greg |
1.1 |
Also, functions (requiring parameters) |
1245 |
|
|
must be given as names and not as expressions. |
1246 |
|
|
.PP |
1247 |
|
|
Constant expressions are used as an optimization in function |
1248 |
|
|
files. |
1249 |
|
|
They are replaced wherever they occur in an expression by their |
1250 |
|
|
value. |
1251 |
|
|
Constant expressions are evaluated only once, so they must not |
1252 |
|
|
contain any variables or values that can change, such as the ray |
1253 |
|
|
variables Px and Ny or the primitive argument function arg(). |
1254 |
|
|
All the math library functions such as sqrt() and cos() have the |
1255 |
|
|
constant attribute, so they will be replaced by immediate values |
1256 |
|
|
whenever they are given constant arguments. |
1257 |
|
|
Thus, the subexpression cos(PI*sqrt(2)) is immediately replaced |
1258 |
|
|
by its value, -.266255342, and does not cause any additional overhead |
1259 |
|
|
in the calculation. |
1260 |
|
|
.PP |
1261 |
|
|
It is generally a good idea to define constants and variables before |
1262 |
|
|
they are referred to in a function file. |
1263 |
|
|
Although evaluation does not take place until later, the interpreter |
1264 |
|
|
does variable scoping and constant subexpression evaluation based on |
1265 |
|
|
what it has compiled already. |
1266 |
|
|
For example, a variable that is defined globally in rayinit.cal then |
1267 |
|
|
referenced in the local context of a function file cannot |
1268 |
|
|
subsequently be redefined in the same file because the compiler |
1269 |
|
|
has already determined the scope of the referenced variable as global. |
1270 |
|
|
To avoid such conflicts, one can state the scope of a variable explicitly |
1271 |
|
|
by preceding the variable name with a context mark (a back-quote) for |
1272 |
|
|
a local variable, or following the name with a context mark for a global |
1273 |
|
|
variable. |
1274 |
|
|
.NH 3 |
1275 |
|
|
Data Files |
1276 |
|
|
.PP |
1277 |
|
|
Data files contain n-dimensional arrays of real numbers used |
1278 |
|
|
for interpolation. |
1279 |
|
|
Typically, definitions in a function file determine how |
1280 |
|
|
to index and use interpolated data values. |
1281 |
|
|
The basic data file format is as follows: |
1282 |
|
|
.DS |
1283 |
|
|
N |
1284 |
|
|
beg1 end1 m1 |
1285 |
|
|
0 0 m2 x2.1 x2.2 x2.3 x2.4 .. x2.m2 |
1286 |
|
|
... |
1287 |
|
|
begN endN mN |
1288 |
|
|
DATA, later dimensions changing faster. |
1289 |
|
|
.DE |
1290 |
|
|
N is the number of dimensions. |
1291 |
|
|
For each dimension, the beginning and ending coordinate |
1292 |
|
|
values and the dimension size is given. |
1293 |
|
|
Alternatively, individual coordinate values can be given when |
1294 |
|
|
the points are not evenly spaced. |
1295 |
|
|
These values must either be increasing or decreasing monotonically. |
1296 |
|
|
The data is m1*m2*...*mN real numbers in ASCII form. |
1297 |
|
|
Comments may appear anywhere in the file, beginning with a pound |
1298 |
|
|
sign ('#') and continuing to the end of line. |
1299 |
|
|
.NH 3 |
1300 |
|
|
Font Files |
1301 |
|
|
.PP |
1302 |
|
|
A font file lists the polygons which make up a character set. |
1303 |
|
|
Comments may appear anywhere in the file, beginning with a pound |
1304 |
|
|
sign ('#') and continuing to the end of line. |
1305 |
|
|
All numbers are decimal integers: |
1306 |
|
|
.DS |
1307 |
|
|
code n |
1308 |
|
|
x0 y0 |
1309 |
|
|
x1 y1 |
1310 |
|
|
... |
1311 |
|
|
xn yn |
1312 |
|
|
... |
1313 |
|
|
.DE |
1314 |
|
|
The ASCII codes can appear in any order. |
1315 |
|
|
N is the number of vertices, and the last is automatically |
1316 |
|
|
connected to the first. |
1317 |
|
|
Separate polygonal sections are joined by coincident sides. |
1318 |
|
|
The character coordinate system is a square with lower left corner at |
1319 |
|
|
(0,0), lower right at (255,0) and upper right at (255,255). |
1320 |
|
|
.NH 2 |
1321 |
|
|
Generators |
1322 |
|
|
.PP |
1323 |
|
|
A generator is any program that produces a scene description |
1324 |
|
|
as its output. |
1325 |
|
|
They usually appear as commands in a scene description file. |
1326 |
|
|
An example of a simple generator is |
1327 |
|
|
.I genbox. |
1328 |
|
|
.I Genbox |
1329 |
|
|
takes the arguments of width, height and depth to produce |
1330 |
|
|
a parallelepiped description. |
1331 |
|
|
.I Genprism |
1332 |
|
|
takes a list of 2-dimensional coordinates and extrudes them along a vector to |
1333 |
|
|
produce a 3-dimensional prism. |
1334 |
|
|
.I Genrev |
1335 |
|
|
is a more sophisticated generator |
1336 |
|
|
that produces an object of rotation from parametric functions |
1337 |
|
|
for radius and axis position. |
1338 |
|
|
.I Gensurf |
1339 |
|
|
tessellates a surface defined by the |
1340 |
|
|
parametric functions x(s,t), y(s,t), and z(s,t). |
1341 |
|
|
.I Genworm |
1342 |
|
|
links cylinders and spheres along a curve. |
1343 |
|
|
.I Gensky |
1344 |
|
|
produces a sun and sky distribution corresponding |
1345 |
|
|
to a given time and date. |
1346 |
|
|
.PP |
1347 |
|
|
.I Xform |
1348 |
|
|
is a program that transforms a scene description from one |
1349 |
|
|
coordinate space to another. |
1350 |
|
|
.I Xform |
1351 |
|
|
does rotation, translation, scaling, and mirroring. |
1352 |
|
|
.NH 1 |
1353 |
|
|
Image Generation |
1354 |
|
|
.PP |
1355 |
|
|
Once the scene has been described in three-dimensions, it |
1356 |
|
|
is possible to generate a two-dimensional image from a |
1357 |
|
|
given perspective. |
1358 |
|
|
.PP |
1359 |
|
|
The image generating programs use an |
1360 |
|
|
.I octree |
1361 |
|
|
to efficiently trace rays through the scene. |
1362 |
|
|
An octree subdivides space into nested octants which |
1363 |
|
|
contain sets of surfaces. |
1364 |
|
|
In RADIANCE, an octree is created from a scene description by |
1365 |
|
|
.I oconv. |
1366 |
|
|
The details of this process are not important, |
1367 |
|
|
but the octree will serve as input to the ray-tracing |
1368 |
|
|
programs and directs the use of a scene description. |
1369 |
|
|
.PP |
1370 |
|
|
.I Rview |
1371 |
|
|
is ray-tracing program for viewing a scene interactively. |
1372 |
|
|
When the user specifies a new perspective, |
1373 |
greg |
1.5 |
.I rvu |
1374 |
greg |
1.1 |
quickly displays a rough |
1375 |
|
|
image on the terminal, then progressively |
1376 |
|
|
increases the resolution as the user looks on. |
1377 |
|
|
He can select a particular section of the image to improve, |
1378 |
|
|
or move to a different view and start over. |
1379 |
|
|
This mode of interaction is useful for debugging scenes |
1380 |
|
|
as well as determining the best view for a final image. |
1381 |
|
|
.PP |
1382 |
|
|
.I Rpict |
1383 |
|
|
produces a high-resolution picture of a scene from |
1384 |
|
|
a particular perspective. |
1385 |
|
|
This program features adaptive sampling, crash |
1386 |
|
|
recovery and progress reporting, all of which are important |
1387 |
|
|
for time-consuming images. |
1388 |
|
|
.PP |
1389 |
|
|
A number of filters are available for manipulating picture files. |
1390 |
|
|
.I Pfilt |
1391 |
|
|
sets the exposure and performs anti-aliasing. |
1392 |
|
|
.I Pcompos |
1393 |
|
|
composites (cuts and pastes) pictures. |
1394 |
|
|
.I Pcond |
1395 |
|
|
conditions a picture for a specific display device. |
1396 |
|
|
.I Pcomb |
1397 |
|
|
performs arbitrary math on one or more pictures. |
1398 |
|
|
.I Protate |
1399 |
|
|
rotates a picture 90 degrees clockwise. |
1400 |
|
|
.I Pflip |
1401 |
|
|
flips a picture horizontally, vertically, or both (180 degree rotation). |
1402 |
|
|
.I Pvalue |
1403 |
|
|
converts a picture to and from simpler formats. |
1404 |
|
|
.PP |
1405 |
|
|
Pictures may be displayed directly under X11 using the program |
1406 |
|
|
.I ximage, |
1407 |
|
|
or converted a standard image format. |
1408 |
|
|
.I Ra_avs |
1409 |
|
|
converts to and from AVS image format. |
1410 |
|
|
.I Ra_pict |
1411 |
|
|
converts to Macintosh 32-bit PICT2 format. |
1412 |
|
|
.I Ra_ppm |
1413 |
|
|
converts to and from Poskanzer Portable Pixmap formats. |
1414 |
|
|
.I Ra_pr |
1415 |
|
|
converts to and from Sun 8-bit rasterfile format. |
1416 |
|
|
.I Ra_pr24 |
1417 |
|
|
converts to and from Sun 24-bit rasterfile format. |
1418 |
|
|
.I Ra_ps |
1419 |
|
|
converts to PostScript color and greyscale formats. |
1420 |
|
|
.I Ra_rgbe |
1421 |
|
|
converts to and from Radiance uncompressed picture format. |
1422 |
|
|
.I Ra_t16 |
1423 |
|
|
converts to and from Targa 16 and 24-bit image formats. |
1424 |
|
|
.I Ra_t8 |
1425 |
|
|
converts to and from Targa 8-bit image format. |
1426 |
|
|
.I Ra_tiff |
1427 |
|
|
converts to and from TIFF. |
1428 |
|
|
.I Ra_xyze |
1429 |
|
|
converts to and from Radiance CIE picture format. |
1430 |
|
|
.NH 1 |
1431 |
|
|
License |
1432 |
|
|
.PP |
1433 |
greg |
1.4 |
.DS |
1434 |
|
|
The Radiance Software License, Version 1.0 |
1435 |
|
|
|
1436 |
|
|
Copyright (c) 1990 - 2002 The Regents of the University of California, |
1437 |
|
|
through Lawrence Berkeley National Laboratory. All rights reserved. |
1438 |
|
|
|
1439 |
|
|
Redistribution and use in source and binary forms, with or without |
1440 |
|
|
modification, are permitted provided that the following conditions |
1441 |
|
|
are met: |
1442 |
|
|
|
1443 |
|
|
1. Redistributions of source code must retain the above copyright |
1444 |
|
|
notice, this list of conditions and the following disclaimer. |
1445 |
|
|
|
1446 |
|
|
2. Redistributions in binary form must reproduce the above copyright |
1447 |
|
|
notice, this list of conditions and the following disclaimer in |
1448 |
|
|
the documentation and/or other materials provided with the |
1449 |
|
|
distribution. |
1450 |
|
|
|
1451 |
|
|
3. The end-user documentation included with the redistribution, |
1452 |
|
|
if any, must include the following acknowledgment: |
1453 |
|
|
"This product includes Radiance software |
1454 |
|
|
(http://radsite.lbl.gov/) |
1455 |
|
|
developed by the Lawrence Berkeley National Laboratory |
1456 |
|
|
(http://www.lbl.gov/)." |
1457 |
|
|
Alternately, this acknowledgment may appear in the software itself, |
1458 |
|
|
if and wherever such third-party acknowledgments normally appear. |
1459 |
|
|
|
1460 |
|
|
4. The names "Radiance," "Lawrence Berkeley National Laboratory" |
1461 |
|
|
and "The Regents of the University of California" must |
1462 |
|
|
not be used to endorse or promote products derived from this |
1463 |
|
|
software without prior written permission. For written |
1464 |
|
|
permission, please contact [email protected]. |
1465 |
|
|
|
1466 |
|
|
5. Products derived from this software may not be called "Radiance", |
1467 |
|
|
nor may "Radiance" appear in their name, without prior written |
1468 |
|
|
permission of Lawrence Berkeley National Laboratory. |
1469 |
|
|
|
1470 |
|
|
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
1471 |
|
|
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
1472 |
|
|
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
1473 |
|
|
DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR |
1474 |
|
|
ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
1475 |
|
|
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
1476 |
|
|
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
1477 |
|
|
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
1478 |
|
|
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
1479 |
|
|
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
1480 |
|
|
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
1481 |
|
|
SUCH DAMAGE. |
1482 |
|
|
.DE |
1483 |
greg |
1.1 |
.NH 1 |
1484 |
|
|
Acknowledgements |
1485 |
|
|
.PP |
1486 |
|
|
This work was supported by the Assistant Secretary of Conservation |
1487 |
|
|
and Renewable Energy, Office of Building Energy Research and |
1488 |
|
|
Development, Buildings Equipment Division of the U.S. Department of |
1489 |
|
|
Energy under Contract No. DE-AC03-76SF00098. |
1490 |
|
|
.PP |
1491 |
|
|
Additional work was sponsored by the Swiss federal government |
1492 |
|
|
under the Swiss LUMEN Project and was |
1493 |
|
|
carried out in the Laboratoire d'Energie Solaire (LESO Group) at |
1494 |
|
|
the Ecole Polytechnique Federale de Lausanne (EPFL University) |
1495 |
|
|
in Lausanne, Switzerland. |
1496 |
|
|
.NH 1 |
1497 |
|
|
References |
1498 |
greg |
1.4 |
.LP |
1499 |
|
|
Ward, G., Elena Eydelberg-Vileshin, |
1500 |
|
|
``Picture Perfect RGB Rendering Using Spectral Prefiltering and |
1501 |
|
|
Sharp Color Primaries,'' |
1502 |
|
|
13th Eurographics Workshop on Rendering, P. Debevec and |
1503 |
|
|
S. Gibson (Editors), June 2002. |
1504 |
|
|
.LP |
1505 |
|
|
Ward, G. and M. Simmons, |
1506 |
|
|
``The Holodeck Ray Cache: An Interactive Rendering System for Global |
1507 |
|
|
Illumination in Nondiffuse Environments,'' |
1508 |
|
|
.I "ACM Transactions on Graphics," |
1509 |
|
|
18(4):361-98, October 1999. |
1510 |
|
|
.LP |
1511 |
|
|
Larson, G.W., H. Rushmeier, C. Piatko, |
1512 |
|
|
``A Visibility Matching Tone Reproduction Operator for High Dynamic |
1513 |
|
|
Range Scenes,'' |
1514 |
|
|
.I "IEEE Transactions on Visualization and Computer Graphics", |
1515 |
|
|
3(4), 291-306, December 1997. |
1516 |
|
|
.LP |
1517 |
|
|
Ward, G., |
1518 |
|
|
``Making Global Illumination User Friendly,'' |
1519 |
|
|
.I "Sixth Eurographics Workshop on Rendering", |
1520 |
|
|
proceedings to be published by Springer-Verlag, |
1521 |
|
|
Dublin, Ireland, June 1995. |
1522 |
|
|
.LP |
1523 |
|
|
Rushmeier, H., G. Ward, C. Piatko, P. Sanders, B. Rust, |
1524 |
|
|
``Comparing Real and Synthetic Images: Some Ideas about Metrics,'' |
1525 |
|
|
.I "Sixth Eurographics Workshop on Rendering", |
1526 |
|
|
proceedings to be published by Springer-Verlag, |
1527 |
|
|
Dublin, Ireland, June 1995. |
1528 |
greg |
1.1 |
.LP |
1529 |
|
|
Ward, G., |
1530 |
|
|
``The Radiance Lighting Simulation and Rendering System,'' |
1531 |
|
|
.I "Computer Graphics", |
1532 |
|
|
Orlando, July 1994. |
1533 |
|
|
.LP |
1534 |
|
|
Rushmeier, H., G. Ward, |
1535 |
|
|
``Energy-Preserving Non-Linear Filters,'' |
1536 |
|
|
.I "Computer Graphics", |
1537 |
|
|
Orlando, July 1994. |
1538 |
|
|
.LP |
1539 |
|
|
Ward, G., |
1540 |
|
|
``A Contrast-Based Scalefactor for Luminance Display,'' |
1541 |
|
|
.I "Graphics Gems IV", |
1542 |
|
|
Edited by Paul Heckbert, |
1543 |
|
|
Academic Press 1994. |
1544 |
|
|
.LP |
1545 |
|
|
Ward, G., |
1546 |
|
|
``Measuring and Modeling Anisotropic Reflection,'' |
1547 |
|
|
.I "Computer Graphics", |
1548 |
|
|
Chicago, July 1992. |
1549 |
|
|
.LP |
1550 |
|
|
Ward, G., P. Heckbert, |
1551 |
|
|
``Irradiance Gradients,'' |
1552 |
|
|
.I "Third Annual Eurographics Workshop on Rendering", |
1553 |
|
|
to be published by Springer-Verlag, held in Bristol, UK, May 1992. |
1554 |
|
|
.LP |
1555 |
|
|
Ward, G., |
1556 |
|
|
``Adaptive Shadow Testing for Ray Tracing,'' |
1557 |
|
|
.I "Second Annual Eurographics Workshop on Rendering", |
1558 |
|
|
to be published by Springer-Verlag, held in Barcelona, SPAIN, May 1991. |
1559 |
|
|
.LP |
1560 |
|
|
Ward, G., |
1561 |
|
|
``Visualization,'' |
1562 |
|
|
.I "Lighting Design and Application", |
1563 |
|
|
Vol. 20, No. 6, June 1990. |
1564 |
|
|
.LP |
1565 |
|
|
Ward, G., F. Rubinstein, R. Clear, |
1566 |
|
|
``A Ray Tracing Solution for Diffuse Interreflection,'' |
1567 |
|
|
.I "Computer Graphics", |
1568 |
|
|
Vol. 22, No. 4, August 1988. |
1569 |
|
|
.LP |
1570 |
|
|
Ward, G., F. Rubinstein, |
1571 |
|
|
``A New Technique for Computer Simulation of Illuminated Spaces,'' |
1572 |
|
|
.I "Journal of the Illuminating Engineering Society", |
1573 |
|
|
Vol. 17, No. 1, Winter 1988. |