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Revision: 1.8
Committed: Sun Jul 24 21:05:45 2005 UTC (18 years, 11 months ago) by greg
Branch: MAIN
CVS Tags: rad3R7P2, rad3R7P1
Changes since 1.7: +2 -2 lines
Log Message:
Updated copyright year

File Contents

# Content
1 .\" RCSid "$Id: ray.1,v 1.7 2004/10/21 16:16:14 greg Exp $"
2 .\" Print using the -ms macro package
3 .DA 1/20/99
4 .LP
5 .tl """Copyright \(co 2005 Regents, University of California
6 .sp 2
7 .TL
8 The
9 .so ../src/rt/VERSION
10 .br
11 Synthetic Imaging System
12 .AU
13 Building Technologies Program
14 .br
15 Lawrence Berkeley Laboratory
16 .br
17 1 Cyclotron Rd., MS 90-3111
18 .br
19 Berkeley, CA 94720
20 .NH 1
21 Introduction
22 .PP
23 RADIANCE was developed as a research tool
24 for predicting the distribution of visible radiation in
25 illuminated spaces.
26 It takes as input a three-dimensional geometric model of
27 the physical environment, and produces a map of
28 spectral radiance values in a color image.
29 The technique of ray-tracing follows light backwards
30 from the image plane to the source(s).
31 Because it can produce realistic images from a simple description,
32 RADIANCE has a wide range of applications in graphic arts,
33 lighting design, computer-aided engineering and architecture.
34 .KF
35 .sp 25
36 .ce
37 .B "Figure 1."
38 .sp
39 .KE
40 .PP
41 The diagram in Figure 1 shows the flow between programs (boxes) and
42 data (ovals).
43 The central program is
44 .I rpict,
45 which produces a picture from a scene description.
46 .I Rview
47 is a variation of
48 .I rpict
49 that computes and displays images interactively.
50 Other programs (not shown) connect many of these elements together,
51 such as the executive programs
52 .I rad
53 and
54 .I ranimate,
55 the interactive rendering program
56 .I rholo,
57 and the animation program
58 .I ranimove.
59 The program
60 .I obj2mesh
61 acts as both a converter and scene compiler, converting a Wavefront .OBJ
62 file into a compiled mesh octree for efficient rendering.
63 .PP
64 A scene description file lists the surfaces and materials
65 that make up a specific environment.
66 The current surface types are spheres, polygons, cones, and cylinders.
67 There is also a composite surface type, called mesh, and a pseudosurface
68 type, called instance, which facilitates very complex geometries.
69 Surfaces can be made from materials such as plastic, metal, and glass.
70 Light sources can be distant disks as well as local spheres, disks
71 and polygons.
72 .PP
73 From a three-dimensional scene description and a specified view,
74 .I rpict
75 produces a two-dimensional image.
76 A picture file is a compressed binary representation of the
77 pixels in the image.
78 This picture can be scaled in size and
79 brightness, anti-aliased, and sent to a graphics output device.
80 .PP
81 A header in each picture file lists the program(s) and
82 parameters that produced it.
83 This is useful for identifying a picture
84 without having to display it.
85 The information can be read by the program
86 .I getinfo.
87 .NH 1
88 Scene Description
89 .PP
90 A scene description file represents a
91 three-dimensional physical environment
92 in Cartesian (rectilinear) world coordinates.
93 It is stored as ASCII text, with the following basic format:
94 .DS
95 # comment
96
97 modifier type identifier
98 n S1 S2 "S 3" .. Sn
99 0
100 m R1 R2 R3 .. Rm
101
102 modifier alias identifier reference
103
104 ! command
105
106 ...
107 .DE
108 .PP
109 A comment line begins with a pound sign, `#'.
110 .PP
111 The scene description
112 .I primitives
113 all have the same general format, and can
114 be either surfaces or modifiers.
115 A primitive has a modifier, a type, and an identifier.
116 A modifier is either the identifier of a
117 .I "previously defined"
118 primitive, or "void"\(dg.
119 .FS
120 \(dgThe most recent definition of a modifier is the one used,
121 and later definitions do not cause relinking of loaded
122 primitives.
123 Thus, the same identifier may be used repeatedly, and each new
124 definition will apply to the primitives following it.
125 .FE
126 An identifier can be any string (i.e., any sequence of non-white characters).
127 The
128 .I arguments
129 associated with a primitive can be strings or real numbers.
130 The first integer following the identifier is the number
131 of string arguments, and it is followed by the arguments themselves
132 (separated by white space or enclosed in quotes).
133 The next integer is the number of integer arguments, and is followed
134 by the integer arguments.
135 (There are currently no primitives that use them, however.)
136 The next integer is the real argument count, and it is followed
137 by the real arguments.
138 .PP
139 An alias gets its type and arguments from a previously defined primitive.
140 This is useful when the same material is used with a different
141 modifier, or as a convenient naming mechanism.
142 The reserved modifier name "inherit" may be used to specificy that
143 an alias will inherit its modifier from the original.
144 Surfaces cannot be aliased.
145 .PP
146 A line beginning with an exclamation point, `!',
147 is interpreted as a command.
148 It is executed by the shell, and its output is read as input to
149 the program.
150 The command must not try to read from its standard input, or
151 confusion will result.
152 A command may be continued over multiple lines using a backslash, `\\',
153 to escape the newline.
154 .PP
155 White space is generally ignored, except as a separator.
156 The exception is the newline character after a command or comment.
157 Commands, comments and primitives may appear in any combination, so long
158 as they are not intermingled.
159 .NH 2
160 Primitive Types
161 .PP
162 Primitives can be surfaces, materials, textures or patterns.
163 Modifiers can be materials, mixtures, textures or patterns.
164 Simple surfaces must have one material in their modifier list.
165 .NH 3
166 Surfaces
167 .PP
168 A scene description will consist mostly of surfaces.
169 The basic types are given below.
170 .LP
171 .UL Source
172 .PP
173 A source is not really a surface, but a solid angle.
174 It is used for specifying light sources that are very distant.
175 The direction to the center of the source and the number of degrees
176 subtended by its disk are given as follows:
177 .DS
178 mod source id
179 0
180 0
181 4 xdir ydir zdir angle
182 .DE
183 .LP
184 .UL Sphere
185 .PP
186 A sphere is given by its center and radius:
187 .DS
188 mod sphere id
189 0
190 0
191 4 xcent ycent zcent radius
192 .DE
193 .LP
194 .UL Bubble
195 .PP
196 A bubble is simply a sphere whose surface normal points inward.
197 .LP
198 .UL Polygon
199 .PP
200 A polygon is given by a list of three-dimensional vertices,
201 which are ordered counter-clockwise as viewed from
202 the front side (into the surface normal).
203 The last vertex is automatically connected to the first.
204 Holes are represented in polygons as interior vertices connected to
205 the outer perimeter by coincident edges (seams).
206 .DS
207 mod polygon id
208 0
209 0
210 3n
211 x1 y1 z1
212 x2 y2 z2
213 ...
214 xn yn zn
215 .DE
216 .LP
217 .UL Cone
218 .PP
219 A cone is a megaphone-shaped object.
220 It is truncated by two planes perpendicular to its axis,
221 and one of its ends may come to a point.
222 It is given as two axis endpoints, and the starting
223 and ending radii:
224 .DS
225 mod cone id
226 0
227 0
228 8
229 x0 y0 z0
230 x1 y1 z1
231 r0 r1
232 .DE
233 .LP
234 .UL Cup
235 .PP
236 A cup is an inverted cone (i.e., has an inward surface normal).
237 .LP
238 .UL Cylinder
239 .PP
240 A cylinder is like a cone, but its starting and ending radii are
241 equal.
242 .DS
243 mod cylinder id
244 0
245 0
246 7
247 x0 y0 z0
248 x1 y1 z1
249 rad
250 .DE
251 .LP
252 .UL Tube
253 .PP
254 A tube is an inverted cylinder.
255 .LP
256 .UL Ring
257 .PP
258 A ring is a circular disk given by its center, surface
259 normal, and inner and outer radii:
260 .DS
261 mod ring id
262 0
263 0
264 8
265 xcent ycent zcent
266 xdir ydir zdir
267 r0 r1
268 .DE
269 .LP
270 .UL Mesh
271 .PP
272 A mesh is a compound surface, made up of many triangles and
273 an octree data structure to accelerate ray intersection.
274 It is typically converted from a Wavefront .OBJ file using the
275 .I obj2mesh
276 program.
277 .DS
278 mod mesh id
279 1+ meshfile transform
280 0
281 0
282 .DE
283 If the modifier is "void", then surfaces will use the modifiers given
284 in the original mesh description.
285 Otherwise, the modifier specified is used in their place.
286 The transform moves the mesh to the desired location in the scene.
287 Multiple instances using the same meshfile take little extra memory,
288 and the compiled mesh itself takes much less space than individual
289 polygons would.
290 In the case of an unsmoothed mesh, using the mesh primitive reduces
291 memory requirements by a factor of 30 relative to individual triangles.
292 If a mesh has smoothed surfaces, we save a factor of 50 or more,
293 permitting very detailed geometries that would otherwise exhaust the
294 available memory.
295 In addition, the mesh primitive can have associated (u,v) coordinates
296 for pattern and texture mapping.
297 These are made available to function files via the Lu and Lv variables.
298 .LP
299 .UL Instance
300 .PP
301 An instance is a compound surface, given by the contents of an
302 octree file (created by oconv).
303 .DS
304 mod instance id
305 1+ octree transform
306 0
307 0
308 .DE
309 If the modifier is "void", then surfaces will use the modifiers given
310 in the original description.
311 Otherwise, the modifier specified is used in their place.
312 The transform moves the octree to the desired location in the scene.
313 Multiple instances using the same octree take little extra memory,
314 hence very complex descriptions can be rendered using this primitive.
315 .PP
316 There are a number of important limitations to be aware of when using
317 instances.
318 First, the scene description used to generate the octree must stand on
319 its own, without referring to modifiers in the parent description.
320 This is necessary for oconv to create the octree.
321 Second, light sources in the octree will not be incorporated correctly
322 in the calculation, and they are not recommended.
323 Finally, there is no advantage (other than convenience) to
324 using a single instance of an octree, or an octree containing only a
325 few surfaces.
326 An xform command on the subordinate description is prefered in such cases.
327 .NH 3
328 Materials
329 .PP
330 A material defines the way light interacts with a surface.
331 The basic types are given below.
332 .LP
333 .UL Light
334 .PP
335 Light is the basic material for self-luminous surfaces (i.e., light
336 sources).
337 In addition to the source surface type, spheres, discs (rings with zero
338 inner radius), cylinders (provided they are long enough), and
339 polygons can act as light sources.
340 Polygons work best when they are rectangular.
341 Cones cannot be used at this time.
342 A pattern may be used to specify a light output distribution.
343 Light is defined simply as a RGB radiance value (watts/steradian/m2):
344 .DS
345 mod light id
346 0
347 0
348 3 red green blue
349 .DE
350 .LP
351 .UL Illum
352 .PP
353 Illum is used for secondary light sources with broad distributions.
354 A secondary light source is treated like any other
355 light source, except when viewed directly.
356 It then acts like it is made of a different material (indicated by
357 the string argument), or becomes invisible (if no string argument is given,
358 or the argument is "void").
359 Secondary sources are useful when modeling windows or
360 brightly illuminated surfaces.
361 .DS
362 mod illum id
363 1 material
364 0
365 3 red green blue
366 .DE
367 .LP
368 .UL Glow
369 .PP
370 Glow is used for surfaces that are self-luminous, but limited
371 in their effect.
372 In addition to the radiance value, a maximum radius for
373 shadow testing is given:
374 .DS
375 mod glow id
376 0
377 0
378 4 red green blue maxrad
379 .DE
380 If maxrad is zero, then the surface will never be tested
381 for shadow, although it may participate in an interreflection calculation.
382 If maxrad is negative, then the surface will never contribute to scene
383 illumination.
384 Glow sources will never illuminate objects on the other side of an
385 illum surface.
386 This provides a convenient way to illuminate local light fixture
387 geometry without overlighting nearby objects.
388 .LP
389 .UL Spotlight
390 .PP
391 Spotlight is used for self-luminous surfaces having directed output.
392 As well as radiance, the full cone angle (in degrees)
393 and orientation (output direction) vector are given.
394 The length of the orientation vector is the distance
395 of the effective focus behind the source center (i.e., the focal length).
396 .DS
397 mod spotlight id
398 0
399 0
400 7 red green blue angle xdir ydir zdir
401 .DE
402 .LP
403 .UL Mirror
404 .PP
405 Mirror is used for planar surfaces that produce secondary
406 source reflections.
407 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 This material is only supported for flat surfaces such as polygons
410 and rings.
411 The arguments are simply the RGB reflectance values, which should be
412 between 0 and 1.
413 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 It can only be used to modify a planar surface (i.e., a polygon or disk)
431 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 If no function file is required (i.e., no special variables or
584 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 Nx, Ny, Nz - surface normal at intersection point
1217 Px, Py, Pz - intersection point
1218 T - distance from start
1219 Ts - single ray (shadow) distance
1220 Rdot - cosine between ray and normal
1221 arg(0) - number of real arguments
1222 arg(i) - i'th real argument
1223 .DE
1224 For mesh objects, the local surface coordinates are available:
1225 .DS
1226 Lu, Lv - local (u,v) coordinates
1227 .DE
1228 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 be kept simple if possible.
1244 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 .I rvu
1374 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 .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 .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 .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 .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.