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feat(rpict,rvu,rtrace,rcontrib): Added "specdata" and "specpict" pattern primitives

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# Content
1 <html>
2 <!-- RCSid $Id: ray.html,v 1.37 2023/12/12 20:25:22 greg Exp $ -->
3 <head>
4 <title>
5 The RADIANCE 6.0 Synthetic Imaging System
6 </title>
7 </head>
8 <body>
9
10 <p>
11
12 <h1>
13 The RADIANCE 6.0 Synthetic Imaging System
14 </h1>
15
16 <p>
17
18 Building Technologies Program<br>
19 Lawrence Berkeley National Laboratory<br>
20 1 Cyclotron Rd., 90-3111<br>
21 Berkeley, CA 94720<br>
22 <a HREF="http://radsite.lbl.gov/radiance"</a>
23 http://radsite.lbl.gov/radiance<br>
24
25 <p>
26 <hr>
27
28 <h2>
29 <a NAME="Overview">Overview</a>
30 </h2>
31 <ol>
32 <li><a HREF="#Intro">Introduction</a><!P>
33 <li><a HREF="#Scene">Scene Description</a><!P>
34 <ol>
35 <li><a HREF="#Primitive"> Primitive Types</a>
36 <ol>
37 <li><a HREF="#Surfaces">Surfaces</a>
38 <li><a HREF="#Materials">Materials</a>
39 <li><a HREF="#Textures">Textures</a>
40 <li><a HREF="#Patterns">Patterns</a>
41 <li><a HREF="#Mixtures">Mixtures</a>
42 </ol><!P>
43 <li><a HREF="#Auxiliary">Auxiliary Files</a>
44 <ol>
45 <li><a HREF="#Function">Function Files</a>
46 <li><a HREF="#Data">Data Files</a>
47 <li><a HREF="#Font">Font Files</a>
48 </ol><!P>
49 <li><a HREF="#Generators">Generators</a>
50 </ol><!P>
51 <li><a HREF="#Image">Image Generation</a><!P>
52 <li><a HREF="#License">License</a><!P>
53 <li><a HREF="#Ack">Acknowledgements</a><!P>
54 <li><a HREF="#Ref">References</a><!P>
55 <li><a HREF="#Index">Types Index</a><!P>
56 </ol>
57
58 <p>
59 <hr>
60
61 <h2>
62 <a NAME="Intro">1. Introduction</a>
63 </h2>
64
65 RADIANCE was developed as a research tool for predicting
66 the distribution of visible radiation in illuminated spaces.
67 It takes as input a three-dimensional geometric model
68 of the physical environment, and produces a map of
69 spectral radiance values in a color image.
70 The technique of ray-tracing follows light backwards
71 from the image plane to the source(s).
72 Because it can produce realistic images from a
73 simple description, RADIANCE has a wide range of applications
74 in graphic arts, lighting design,
75 computer-aided engineering and architecture.
76
77 <p>
78 <img SRC="diagram1.gif">
79 <p>
80 Figure 1
81 <p>
82 The diagram in Figure 1 shows the flow between programs (boxes) and data
83 (ovals).
84 The central program is <i>rpict</i>, which produces a picture from a scene
85 description.
86 <i>Rvu</i> is a variation of rpict that computes and displays images
87 interactively, and rtrace computes single ray values.
88 Other programs (not shown) connect many of these elements together,
89 such as the executive programs
90 <i>rad</i>
91 and
92 <i>ranimate</i>,
93 the interactive rendering program
94 <i>rholo</i>,
95 and the animation program
96 <i>ranimove</i>.
97 The program
98 <i>obj2mesh</i>
99 acts as both a converter and scene compiler, converting a Wavefront .OBJ
100 file into a compiled mesh octree for efficient rendering.
101
102 <p>
103 A scene description file lists the surfaces and materials
104 that make up a specific environment.
105 The current surface types are spheres, polygons, cones, and cylinders.
106 There is also a composite surface type, called mesh, and a pseudosurface
107 type, called instance, which facilitates very complex geometries.
108 Surfaces can be made from materials such as plastic, metal, and glass.
109 Light sources can be distant disks as well as local spheres, disks
110 and polygons.
111
112 <p>
113 From a three-dimensional scene description and a specified view,
114 <i>rpict</i> produces a two-dimensional image.
115 A picture file is a compressed binary representation of the
116 pixels in the image.
117 This picture can be scaled in size and brightness,
118 anti-aliased, and sent to a graphics output device.
119
120 <p>
121 A header in each picture file lists the program(s)
122 and parameters that produced it.
123 This is useful for identifying a picture without having to display it.
124 The information can be read by the program <i>getinfo</i>.
125
126 <p>
127 <hr>
128
129 <h2>
130 <a name="Scene">2. Scene Description</a>
131 </h2>
132
133 A scene description file represents a three-dimensional physical environment in Cartesian (rectilinear) world coordinates.
134 It is stored as ASCII text, with the following basic format:
135
136 <pre>
137 # comment
138
139 modifier type identifier
140 n S1 S2 &quot;S 3&quot; .. Sn
141 0
142 m R1 R2 R3 .. Rm
143
144 modifier alias identifier reference
145
146 ! command
147
148 ...
149 </pre>
150
151 A comment line begins with a pound sign, `#'.
152
153 <p>
154 The <a NAME="scene_desc">scene description primitives</a>
155 all have the same general format, and can be either surfaces or modifiers.
156 A primitive has a modifier, a type, and an identifier.
157 <p>
158 A <a NAME="modifier"><b>modifier</b></a> is either the
159 identifier of a previously defined primitive, or &quot;void&quot;.
160 <br>
161 [ The most recent definition of a modifier is the
162 one used, and later definitions do not cause relinking
163 of loaded primitives.
164 Thus, the same identifier may be used repeatedly,
165 and each new definition will apply to the primitives following it. ]
166 <p>
167 An <a NAME="identifier"><b>identifier</b></a> can be any string
168 (i.e., any sequence of non-white characters).
169 <p>
170 The arguments associated with a primitive can be strings or real numbers.
171 <ul>
172 <li> The first integer following the identifier is the number of <b>string arguments</b>,
173 and it is followed by the arguments themselves (separated by white space or enclosed in quotes).
174 <li> The next integer is the number of integer arguments, and is followed by the <b>integer arguments</b>.
175 (There are currently no primitives that use them, however.)
176 <li> The next integer is the real argument count, and it is followed by the <b>real arguments</b>.
177 </ul>
178
179 <p>
180 An <a NAME="alias"><b>alias</b></a> gets its type and arguments from
181 a previously defined primitive.
182 This is useful when the same material is
183 used with a different modifier, or as a convenient naming mechanism.
184 The reserved modifier name &quot;inherit&quot; may be used to specificy that
185 an alias will inherit its modifier from the original.
186 Surfaces cannot be aliased.
187
188 <p>
189 A line beginning with an exclamation point, `!',
190 is interpreted as a command.
191 It is executed by the shell, and its output is read as input to the program.
192 The command must not try to read from its standard input, or confusion
193 will result.
194 A command may be continued over multiple lines using a
195 backslash, `\', to escape the newline.
196
197 <p>
198 White space is generally ignored, except as a separator.
199 The exception is the newline character after a command or comment.
200 Commands, comments and primitives may appear in any
201 combination, so long as they are not intermingled.
202
203 <p>
204 <hr>
205
206 <h3>
207 <a NAME="Primitive">2.1. Primitive Types</a>
208 </h3>
209
210 Primitives can be <a HREF="#Surfaces">surfaces</a>,
211 <a HREF="#Materials">materials</a>,
212 <a HREF="#Textures">textures</a> or
213 <a HREF="#Patterns">patterns</a>.
214 Modifiers can be <a HREF="#Materials">materials</a>,
215 <a HREF="#Mixtures">mixtures</a>,
216 <a HREF="#Textures">textures</a> or <a HREF="#Patterns">patterns</a>.
217 Simple surfaces must have one material in their modifier list.
218
219 <p>
220 <hr>
221
222 <h4>
223 <a NAME="Surfaces">2.1.1. Surfaces</a>
224 </h4>
225 <dl>
226
227 A scene description will consist mostly of surfaces.
228 The basic types are given below.
229
230 <p>
231
232 <dt>
233 <a NAME="Source">
234 <b>Source </b>
235 </a>
236 <dd>
237 A source is not really a surface, but a solid angle.
238 It is used for specifying light sources that are very distant.
239 The direction to the center of the source and the number of degrees subtended by its disk are given as follows:
240
241 <pre>
242 mod source id
243 0
244 0
245 4 xdir ydir zdir angle
246 </pre>
247
248 <p>
249
250 <dt>
251 <a NAME="Sphere">
252 <b>Sphere</b>
253 </a>
254 <dd>
255 A sphere is given by its center and radius:
256
257 <pre>
258 mod sphere id
259 0
260 0
261 4 xcent ycent zcent radius
262 </pre>
263
264 <p>
265
266 <dt>
267 <a NAME="Bubble">
268 <b>Bubble</b>
269 </a>
270
271 <dd>
272 A bubble is simply a sphere whose surface normal points inward.
273
274 <p>
275
276 <dt>
277 <a NAME="Polygon">
278 <b>Polygon</b>
279 </a>
280 <dd>
281 A polygon is given by a list of three-dimensional vertices,
282 which are ordered counter-clockwise as viewed from the
283 front side (into the surface normal).
284 The last vertex is automatically connected to the first.
285 Holes are represented in polygons as interior vertices
286 connected to the outer perimeter by coincident edges (seams).
287
288 <pre>
289 mod polygon id
290 0
291 0
292 3n
293 x1 y1 z1
294 x2 y2 z2
295 ...
296 xn yn zn
297 </pre>
298
299 <p>
300
301 <dt>
302 <a NAME="Cone">
303 <b>Cone</b>
304 </a>
305 <dd>
306 A cone is a megaphone-shaped object.
307 It is truncated by two planes perpendicular to its axis,
308 and one of its ends may come to a point.
309 It is given as two axis endpoints, and the starting and ending radii:
310
311 <pre>
312 mod cone id
313 0
314 0
315 8
316 x0 y0 z0
317 x1 y1 z1
318 r0 r1
319 </pre>
320
321 <p>
322
323 <dt>
324 <a NAME="Cup">
325 <b>Cup</b>
326 </a>
327 <dd>
328 A cup is an inverted <a HREF="#Cone">cone</a> (i.e., has an
329 inward surface normal).
330
331 <p>
332
333 <dt>
334 <a NAME="Cylinder">
335 <b>Cylinder</b>
336 </a>
337 <dd>
338 A cylinder is like a <a HREF="#Cone">cone</a>, but its
339 starting and ending radii are equal.
340
341 <pre>
342 mod cylinder id
343 0
344 0
345 7
346 x0 y0 z0
347 x1 y1 z1
348 rad
349 </pre>
350
351 <p>
352
353 <dt>
354 <a NAME="Tube">
355 <b>Tube</b>
356 </a>
357 <dd>
358 A tube is an inverted <a HREF="#Cylinder">cylinder</a>.
359
360 <p>
361
362 <dt>
363 <a NAME="Ring">
364 <b>Ring</b>
365 </a>
366 <dd>
367 A ring is a circular disk given by its center,
368 surface normal, and inner and outer radii:
369
370 <pre>
371 mod ring id
372 0
373 0
374 8
375 xcent ycent zcent
376 xdir ydir zdir
377 r0 r1
378 </pre>
379
380 <p>
381
382 <dt>
383 <a NAME="Instance">
384 <b>Instance</b>
385 </a>
386 <dd>
387 An instance is a compound surface, given
388 by the contents of an octree file (created by oconv).
389
390 <pre>
391 mod instance id
392 1+ octree transform
393 0
394 0
395 </pre>
396
397 If the modifier is &quot;void&quot;, then surfaces will
398 use the modifiers given in the original description.
399 Otherwise, the modifier specified is used in their place.
400 The transform moves the octree to the desired location in the scene.
401 Multiple instances using the same octree take
402 little extra memory, hence very complex
403 descriptions can be rendered using this primitive.
404
405 <p>
406 There are a number of important limitations to be aware of
407 when using instances.
408 First, the scene description used to generate the octree must
409 stand on its own, without referring to modifiers in the
410 parent description.
411 This is necessary for oconv to create the octree.
412 Second, light sources in the octree will not be
413 incorporated correctly in the calculation,
414 and they are not recommended.
415 Finally, there is no advantage (other than
416 convenience) to using a single instance of an octree,
417 or an octree containing only a few surfaces.
418 An <a HREF="../man_html/xform.1.html">xform</a> command
419 on the subordinate description is prefered in such cases.
420 </dl>
421
422 <p>
423
424 <dt>
425 <a NAME="Mesh">
426 <b>Mesh</b>
427 </a>
428 <dd>
429 A mesh is a compound surface, made up of many triangles and
430 an octree data structure to accelerate ray intersection.
431 It is typically converted from a Wavefront .OBJ file using the
432 <i>obj2mesh</i> program.
433
434 <pre>
435 mod mesh id
436 1+ meshfile transform
437 0
438 0
439 </pre>
440
441 If the modifier is &quot;void&quot;, then surfaces will
442 use the modifiers given in the original mesh description.
443 Otherwise, the modifier specified is used in their place.
444 The transform moves the mesh to the desired location in the scene.
445 Multiple instances using the same meshfile take little extra memory,
446 and the compiled mesh itself takes much less space than individual
447 polygons would.
448 In the case of an unsmoothed mesh, using the mesh primitive reduces
449 memory requirements by a factor of 30 relative to individual triangles.
450 If a mesh has smoothed surfaces, we save a factor of 50 or more,
451 permitting very detailed geometries that would otherwise exhaust the
452 available memory.
453 In addition, the mesh primitive can have associated (u,v) coordinates
454 for pattern and texture mapping.
455 These are made available to function files via the Lu and Lv variables.
456
457 </dl>
458
459 <p>
460 <hr>
461
462 <h4>
463 <a NAME="Materials">2.1.2. Materials</a>
464 </h4>
465
466 A material defines the way light interacts with a surface. The basic types are given below.
467
468 <p>
469
470 <dl>
471
472 <dt>
473 <a NAME="Light">
474 <b>Light</b>
475 </a>
476 <dd>
477 Light is the basic material for self-luminous surfaces (i.e.,
478 light sources).
479 In addition to the <a HREF="#Source">source</a> surface type,
480 <a HREF="#Sphere">spheres</a>,
481 discs (<a HREF="#Ring">rings</a> with zero inner radius),
482 <a HREF="#Cylinder">cylinders</a> (provided they are long enough), and <a HREF="#Polygon">polygons</a> can act as light sources.
483 Polygons work best when they are rectangular.
484 Cones cannot be used at this time.
485 A pattern may be used to specify a light output distribution.
486 Light is defined simply as a RGB radiance value (watts/steradian/m2):
487
488 <pre>
489 mod light id
490 0
491 0
492 3 red green blue
493 </pre>
494
495 <p>
496
497 <dt>
498 <a NAME="Illum">
499 <b>Illum</b>
500 </a>
501
502 <dd>
503 Illum is used for secondary light sources with broad distributions.
504 A secondary light source is treated like any other light source, except when viewed directly.
505 It then acts like it is made of a different material (indicated by
506 the string argument), or becomes invisible (if no string argument is given,
507 or the argument is &quot;void&quot;).
508 Secondary sources are useful when modeling windows or brightly illuminated surfaces.
509
510 <pre>
511 mod illum id
512 1 material
513 0
514 3 red green blue
515 </pre>
516
517 <p>
518
519 <dt>
520 <a NAME="Glow">
521 <b>Glow</b>
522 </a>
523
524 <dd>
525 Glow is used for surfaces that are self-luminous, but limited in their effect.
526 In addition to the radiance value, a maximum radius for shadow testing is given:
527
528 <pre>
529 mod glow id
530 0
531 0
532 4 red green blue maxrad
533 </pre>
534
535 If maxrad is zero, then the surface will never be tested for shadow, although it may participate in an interreflection calculation.
536 If maxrad is negative, then the surface will never contribute to scene illumination.
537 Glow sources will never illuminate objects on the other side of an illum surface.
538 This provides a convenient way to illuminate local light fixture geometry without overlighting nearby objects.
539
540 <p>
541
542 <dt>
543 <a NAME="Spotlight">
544 <b>Spotlight</b>
545 </a>
546
547 <dd>
548 Spotlight is used for self-luminous surfaces having directed output.
549 As well as radiance, the full cone angle (in degrees) and orientation (output direction) vector are given.
550 The length of the orientation vector is the distance of the effective
551 focus behind the source center (i.e., the focal length).
552
553 <pre>
554 mod spotlight id
555 0
556 0
557 7 red green blue angle xdir ydir zdir
558 </pre>
559
560 <p>
561
562 <dt>
563 <a NAME="Mirror">
564 <b>Mirror</b>
565 </a>
566
567 <dd>
568 Mirror is used for planar surfaces that produce virtual source reflections.
569 This material should be used sparingly, as it may cause the light source calculation to blow up if it is applied to many small surfaces.
570 This material is only supported for flat surfaces such as <a HREF="#Polygon">polygons</a> and <a HREF="#Ring">rings</a>.
571 The arguments are simply the RGB reflectance values, which should be between 0 and 1.
572 An optional string argument may be used like the illum type to specify a different material to be used for shading non-source rays.
573 If this alternate material is given as &quot;void&quot;, then the mirror surface will be invisible.
574 This is only appropriate if the surface hides other (more detailed) geometry with the same overall reflectance.
575
576 <pre>
577 mod mirror id
578 1 material
579 0
580 3 red green blue
581 </pre>
582
583 <p>
584
585 <dt>
586 <a NAME="Prism1">
587 <b>Prism1</b>
588 </a>
589
590 <dd>
591 The prism1 material is for general light redirection from prismatic glazings, generating virtual light sources.
592 It can only be used to modify a planar surface
593 (i.e., a <a HREF="#Polygon">polygon</a> or <a HREF="#Ring">disk</a>)
594 and should not result in either light concentration or scattering.
595 The new direction of the ray can be on either side of the material,
596 and the definitions must have the correct bidirectional properties to work properly with virtual light sources.
597 The arguments give the coefficient for the redirected light and its direction.
598
599 <pre>
600 mod prism1 id
601 5+ coef dx dy dz funcfile transform
602 0
603 n A1 A2 .. An
604 </pre>
605
606 The new direction variables dx, dy and dz need not produce a normalized vector.
607 For convenience, the variables DxA, DyA and DzA are defined as the normalized direction to the target light source.
608 See <a HREF="#Function">section 2.2.1</a> on function files for further information.
609
610 <p>
611
612 <dt>
613 <a NAME="Prism2">
614 <b>Prism2</b>
615 </a>
616
617 <dd>
618 The material prism2 is identical to <a HREF="#Prism1">prism1</a> except that it provides for two ray redirections rather than one.
619
620 <pre>
621 mod prism2 id
622 9+ coef1 dx1 dy1 dz1 coef2 dx2 dy2 dz2 funcfile transform
623 0
624 n A1 A2 .. An
625 </pre>
626
627 <p>
628
629 <dt>
630 <a NAME="Mist">
631 <b>Mist</b>
632 </a>
633
634 <dd>
635 Mist is a virtual material used to delineate a volume
636 of participating atmosphere.
637 A list of important light sources may be given, along with an
638 extinction coefficient, scattering albedo and scattering eccentricity
639 parameter.
640 The light sources named by the string argument list
641 will be tested for scattering within the volume.
642 Sources are identified by name, and virtual light sources may be indicated
643 by giving the relaying object followed by '&gt;' followed by the source, i.e:
644
645 <pre>
646 3 source1 mirror1&gt;source10 mirror2&gt;mirror1&gt;source3
647 </pre>
648
649 Normally, only one source is given per mist material, and there is an
650 upper limit of 32 to the total number of active scattering sources.
651 The extinction coefficient, if given, is added the the global
652 coefficient set on the command line.
653 Extinction is in units of 1/distance (distance based on the world coordinates),
654 and indicates the proportional loss of radiance over one unit distance.
655 The scattering albedo, if present, will override the global setting within
656 the volume.
657 An albedo of 0 0 0 means a perfectly absorbing medium, and an albedo of
658 1 1 1 means
659 a perfectly scattering medium (no absorption).
660 The scattering eccentricity parameter will likewise override the global
661 setting if it is present.
662 Scattering eccentricity indicates how much scattered light favors the
663 forward direction, as fit by the Henyey-Greenstein function:
664
665 <pre>
666 P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5
667 </pre>
668
669 A perfectly isotropic scattering medium has a g parameter of 0, and
670 a highly directional material has a g parameter close to 1.
671 Fits to the g parameter may be found along with typical extinction
672 coefficients and scattering albedos for various atmospheres and
673 cloud types in USGS meteorological tables.
674 (A pattern will be applied to the extinction values.)
675
676 <pre>
677 mod mist id
678 N src1 src2 .. srcN
679 0
680 0|3|6|7 [ rext gext bext [ ralb galb balb [ g ] ] ]
681 </pre>
682
683 There are two usual uses of the mist type.
684 One is to surround a beam from a spotlight or laser so that it is
685 visible during rendering.
686 For this application, it is important to use a <a HREF="#Cone">cone</a>
687 (or <a HREF="#Cylinder">cylinder</a>) that
688 is long enough and wide enough to contain the important visible portion.
689 Light source photometry and intervening objects will have the desired
690 effect, and crossing beams will result in additive scattering.
691 For this application, it is best to leave off the real arguments, and
692 use the global rendering parameters to control the atmosphere.
693 The second application is to model clouds or other localized media.
694 Complex boundary geometry may be used to give shape to a uniform medium,
695 so long as the boundary encloses a proper volume.
696 Alternatively, a pattern may be used to set the line integral value
697 through the cloud for a ray entering or exiting a point in a given
698 direction.
699 For this application, it is best if cloud volumes do not overlap each other,
700 and opaque objects contained within them may not be illuminated correctly
701 unless the line integrals consider enclosed geometry.
702
703 <dt>
704 <a NAME="Plastic">
705 <b>Plastic</b>
706 </a>
707
708 <dd>
709 Plastic is a material with uncolored highlights.
710 It is given by its RGB reflectance, its fraction of specularity, and its roughness value.
711 Roughness is specified as the rms slope of surface facets.
712 A value of 0 corresponds to a perfectly smooth surface, and a value of 1 would be a very rough surface.
713 Specularity fractions greater than 0.1 and roughness values greater than 0.2 are not very realistic.
714 (A pattern modifying plastic will affect the material color.)
715
716 <pre>
717 mod plastic id
718 0
719 0
720 5 red green blue spec rough
721 </pre>
722
723 <p>
724
725 <dt>
726 <a NAME="Metal">
727 <b>Metal</b>
728 </a>
729
730 <dd>
731 Metal is similar to <a HREF="#Plastic">plastic</a>, but specular highlights are modified by the material color.
732 Specularity of metals is usually .9 or greater.
733 As for plastic, roughness values above .2 are uncommon.
734
735 <p>
736
737 <dt>
738 <a NAME="Trans">
739 <b>Trans</b>
740 </a>
741
742 <dd>
743 Trans is a translucent material, similar to <a HREF="#Plastic">plastic</a>.
744 The transmissivity is the fraction of penetrating light that travels all the way through the material.
745 The transmitted specular component is the fraction of transmitted light that is not diffusely scattered.
746 Transmitted and diffusely reflected light is modified by the material color.
747 Translucent objects are infinitely thin.
748
749 <pre>
750 mod trans id
751 0
752 0
753 7 red green blue spec rough trans tspec
754 </pre>
755
756 <p>
757
758 <dt>
759 <a NAME="Plastic2">
760 <b>Plastic2</b>
761 </a>
762
763 <dd>
764 Plastic2 is similar to <a HREF="#Plastic">plastic</a>, but with anisotropic roughness.
765 This means that highlights in the surface will appear elliptical rather than round.
766 The orientation of the anisotropy is determined by the unnormalized direction vector ux uy uz.
767 These three expressions (separated by white space) are evaluated in the context of the function file funcfile.
768 If no function file is required (i.e., no special variables or functions are required), a period (`.') may be given in its place.
769 (See the discussion of <a HREF="#Function">Function Files</a> in the Auxiliary Files section).
770 The urough value defines the roughness along the u vector given projected onto the surface.
771 The vrough value defines the roughness perpendicular to this vector.
772 Note that the highlight will be narrower in the direction of the smaller roughness value.
773 Roughness values of zero are not allowed for efficiency reasons since the behavior would be the same as regular plastic in that case.
774
775 <pre>
776 mod plastic2 id
777 4+ ux uy uz funcfile transform
778 0
779 6 red green blue spec urough vrough
780 </pre>
781
782 <p>
783
784 <dt>
785 <a NAME="Metal2">
786 <b>Metal2</b>
787 </a>
788
789 <dd>
790 Metal2 is the same as <a HREF="#Plastic2">plastic2</a>, except that the highlights are modified by the material color.
791
792 <p>
793
794 <dt>
795 <a NAME="Trans2">
796 <b>Trans2</b>
797 </a>
798
799 <dd>
800 Trans2 is the anisotropic version of <a HREF="#Trans">trans</a>.
801 The string arguments are the same as for <a HREF="#Plastic2">plastic2</a>,
802 and the real arguments are the same as for trans but with an additional roughness value.
803
804 <pre>
805 mod trans2 id
806 4+ ux uy uz funcfile transform
807 0
808 8 red green blue spec urough vrough trans tspec
809 </pre>
810
811 <p>
812
813 <dt>
814 <a NAME="Ashik2">
815 <b>Ashik2</b>
816 </a>
817
818 <dd>
819 Ashik2 is the anisotropic reflectance model by Ashikhmin & Shirley.
820 The string arguments are the same as for <a HREF="#Plastic2">plastic2</a>, but the real
821 arguments have additional flexibility to specify the specular color.
822 Also, rather than roughness, specular power is used, which has no
823 physical meaning other than larger numbers are equivalent to a smoother
824 surface.
825 Unlike other material types, total reflectance is the sum of
826 diffuse and specular colors, and should be adjusted accordingly.
827 <pre>
828 mod ashik2 id
829 4+ ux uy uz funcfile transform
830 0
831 8 dred dgrn dblu sred sgrn sblu u-power v-power
832 </pre>
833
834 <p>
835
836 <dt>
837 <a NAME="Dielectric">
838 <b>Dielectric</b>
839 </a>
840
841 <dd>
842 A dielectric material is transparent, and it refracts light as well as reflecting it.
843 Its behavior is determined by the index of refraction and transmission coefficient in each wavelength band per unit length.
844 Common glass has a index of refraction (n) around 1.5, and a transmission coefficient of roughly 0.92 over an inch.
845 An additional number, the Hartmann constant, describes how the index of refraction changes as a function of wavelength.
846 It is usually zero. (A <a HREF="#Patterns">pattern</a> modifies only the refracted value.)
847
848 <pre>
849 mod dielectric id
850 0
851 0
852 5 rtn gtn btn n hc
853 </pre>
854
855 <p>
856
857 <dt>
858 <a NAME="Interface">
859 <b>Interface</b>
860 </a>
861
862 <dd>
863 An interface is a boundary between two dielectrics.
864 The first transmission coefficient and refractive index are for the inside; the second ones are for the outside.
865 Ordinary dielectrics are surrounded by a vacuum (1 1 1 1).
866
867 <pre>
868 mod interface id
869 0
870 0
871 8 rtn1 gtn1 btn1 n1 rtn2 gtn2 btn2 n2
872 </pre>
873
874 <p>
875
876 <dt>
877 <a NAME="Glass">
878 <b>Glass</b>
879 </a>
880
881 <dd>
882 Glass is similar to <a HREF="#Dielectric">dielectric</a>, but it is optimized for thin glass surfaces (n = 1.52).
883 One transmitted ray and one reflected ray is produced.
884 By using a single surface is in place of two, internal reflections are avoided.
885 The surface orientation is irrelevant, as it is for <a HREF="#Plastic">plastic</a>, <a HREF="#Metal">metal</a>, and <a HREF="#Trans">trans</a>.
886 The only specification required is the transmissivity at normal incidence.
887 (Transmissivity is the amount of light not absorbed in one traversal
888 of the material.
889 Transmittance -- the value usually measured -- is the total light
890 transmitted through the pane including multiple reflections.)
891 To compute transmissivity (tn) from transmittance (Tn) use:
892
893 <pre>
894 tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
895 </pre>
896
897 Standard 88% transmittance glass has a transmissivity of 0.96.
898 (A <a HREF="#Patterns">pattern</a> modifying glass will affect the transmissivity.)
899 If a fourth real argument is given, it is interpreted as the index of refraction to use instead of 1.52.
900
901 <pre>
902 mod glass id
903 0
904 0
905 3 rtn gtn btn
906 </pre>
907
908 <p>
909
910 <dt>
911 <a NAME="Plasfunc">
912 <b>Plasfunc</b>
913 </a>
914
915 <dd>
916 Plasfunc in used for the procedural definition of plastic-like materials
917 with arbitrary bidirectional reflectance distribution functions (BRDF's).
918 The arguments to this material include the color and specularity,
919 as well as the function defining the specular distribution and the auxiliary file where it may be found.
920
921 <pre>
922 mod plasfunc id
923 2+ refl funcfile transform
924 0
925 4+ red green blue spec A5 ..
926 </pre>
927
928 The function refl takes four arguments, the x, y and z
929 direction towards the incident light, and the solid angle
930 subtended by the source.
931 The solid angle is provided to facilitate averaging, and is usually
932 ignored.
933 The refl function should integrate to 1 over
934 the projected hemisphere to maintain energy balance.
935 At least four real arguments must be given, and these are made available along with any additional values to the reflectance function.
936 Currently, only the contribution from direct light sources is considered in the specular calculation.
937 As in most material types, the surface normal is always altered to face the incoming ray.
938
939 <p>
940
941 <dt>
942 <a NAME="Metfunc">
943 <b>Metfunc</b>
944 </a>
945
946 <dd>
947 Metfunc is identical to <a HREF="#Plasfunc">plasfunc</a> and takes the same arguments,
948 but the specular component is multiplied also by the material color.
949
950 <p>
951
952 <dt>
953 <a NAME="Transfunc">
954 <b>Transfunc</b>
955 </a>
956
957 <dd>
958 Transfunc is similar to <a HREF="#Plasfunc">plasfunc</a> but with an arbitrary bidirectional transmittance distribution
959 as well as a reflectance distribution.
960 Both reflectance and transmittance are specified with the same function.
961
962 <pre>
963 mod transfunc id
964 2+ brtd funcfile transform
965 0
966 6+ red green blue rspec trans tspec A7 ..
967 </pre>
968
969 Where trans is the total light transmitted and tspec is the non-Lambertian fraction of transmitted light.
970 The function brtd should integrate to 1 over each projected hemisphere.
971
972 <p>
973
974 <dt>
975 <a NAME="BRTDfunc">
976 <b>BRTDfunc</b>
977 </a>
978
979 <dd>
980 The material BRTDfunc gives the maximum flexibility over surface reflectance and transmittance,
981 providing for spectrally-dependent specular rays and reflectance and transmittance distribution functions.
982
983 <pre>
984 mod BRTDfunc id
985 10+ rrefl grefl brefl
986 rtrns gtrns btrns
987 rbrtd gbrtd bbrtd
988 funcfile transform
989 0
990 9+ rfdif gfdif bfdif
991 rbdif gbdif bbdif
992 rtdif gtdif btdif
993 A10 ..
994 </pre>
995
996 The variables rrefl, grefl and brefl specify the color coefficients for the ideal specular (mirror) reflection of the surface.
997 The variables rtrns, gtrns and btrns specify the color coefficients for the ideal specular transmission.
998 The functions rbrtd, gbrtd and bbrtd take the direction to the incident light (and its solid angle) and
999 compute the color coefficients for the directional diffuse part of reflection and transmission.
1000 As a special case, three identical values of '0' may be given in place of these function names to indicate no directional diffuse component.
1001
1002 <p>
1003 Unlike most other material types, the surface normal is not altered to face the incoming ray.
1004 Thus, functions and variables must pay attention to the orientation of the surface and make adjustments appropriately.
1005 However, the special variables for the perturbed dot product and surface normal, RdotP, NxP, NyP and NzP are reoriented
1006 as if the ray hit the front surface for convenience.
1007
1008 <p>
1009 A diffuse reflection component may be given for the front side with rfdif, gfdif and bfdif for the front side of the surface
1010 or rbdif, gbdif and bbdif for the back side.
1011 The diffuse transmittance (must be the same for both sides by physical law) is given by rtdif, gtdif and btdif.
1012 A pattern will modify these diffuse scattering values, and will be available through the special variables CrP, CgP and CbP.
1013
1014 <p>
1015 Care must be taken when using this material type to produce a physically valid reflection model.
1016 The reflectance functions should be bidirectional, and under no circumstances should the sum of reflected diffuse,
1017 transmitted diffuse, reflected specular, transmitted specular and the integrated directional diffuse component be greater than one.
1018
1019 <p>
1020
1021 <dt>
1022 <a NAME="Plasdata">
1023 <b>Plasdata</b>
1024 </a>
1025
1026 <dd>
1027 Plasdata is used for arbitrary BRDF's that are most conveniently given as interpolated data.
1028 The arguments to this material are the <a HREF="#Data">data file</a> and coordinate index functions,
1029 as well as a function to optionally modify the data values.
1030
1031 <pre>
1032 mod plasdata id
1033 3+n+
1034 func datafile
1035 funcfile x1 x2 .. xn transform
1036 0
1037 4+ red green blue spec A5 ..
1038 </pre>
1039
1040 The coordinate indices (x1, x2, etc.) are themselves functions of the x, y and z direction to the incident light, plus the solid angle
1041 subtended by the light source (usually ignored).
1042 The data function (func) takes five variables, the
1043 interpolated value from the n-dimensional data file, followed by the
1044 x, y and z direction to the incident light and the solid angle of the source.
1045 The light source direction and size may of course be ignored by the function.
1046
1047 <p>
1048
1049 <dt>
1050 <a NAME="Metdata">
1051 <b>Metdata</b>
1052 </a>
1053
1054 <dd>
1055 As metfunc is to plasfunc, metdata is to <a HREF="#Plasdata">plasdata</a>.
1056 Metdata takes the same arguments as plasdata, but the specular component is modified by the given material color.
1057
1058 <p>
1059
1060 <dt>
1061 <a NAME="Transdata">
1062 <b>Transdata</b>
1063 </a>
1064
1065 <dd>
1066 Transdata is like <a HREF="#Plasdata">plasdata</a> but the specification includes transmittance as well as reflectance.
1067 The parameters are as follows.
1068
1069 <pre>
1070 mod transdata id
1071 3+n+
1072 func datafile
1073 funcfile x1 x2 .. xn transform
1074 0
1075 6+ red green blue rspec trans tspec A7 ..
1076 </pre>
1077
1078 <p>
1079
1080 <dt>
1081 <a NAME="BSDF">
1082 <b>BSDF</b>
1083 </a>
1084
1085 <dd>
1086 The BSDF material type loads an XML (eXtensible Markup Language)
1087 file describing a bidirectional scattering distribution function.
1088 Real arguments to this material may define additional
1089 diffuse components that augment the BSDF data.
1090 String arguments are used to define thickness for proxied
1091 surfaces and the &quot;up&quot; orientation for the material.
1092
1093 <pre>
1094 mod BSDF id
1095 6+ thick BSDFfile ux uy uz funcfile transform
1096 0
1097 0|3|6|9
1098 rfdif gfdif bfdif
1099 rbdif gbdif bbdif
1100 rtdif gtdif btdif
1101 </pre>
1102
1103 <p>
1104 The first string argument is a &quot;thickness&quot; parameter that may be used
1105 to hide detail geometry being proxied by an aggregate BSDF material.
1106 If a view or shadow ray hits a BSDF proxy with non-zero thickness,
1107 it will pass directly through as if the surface were not there.
1108 Similar to the illum type, this permits direct viewing and
1109 shadow testing of complex geometry.
1110 The BSDF is used when a scattered (indirect) ray hits the surface,
1111 and any transmitted sample rays will be offset by the thickness amount
1112 to avoid the hidden geometry and gather samples from the other side.
1113 In this manner, BSDF surfaces can improve the results for indirect
1114 scattering from complex systems without sacrificing appearance or
1115 shadow accuracy.
1116 If the BSDF has transmission and back-side reflection data,
1117 a parallel BSDF surface may be
1118 placed slightly less than the given thickness away from the front surface
1119 to enclose the complex geometry on both sides.
1120 The sign of the thickness is important, as it indicates
1121 whether the proxied geometry is behind the BSDF
1122 surface (when thickness is positive) or in front (when
1123 thickness is negative).
1124 <p>
1125 The second string argument is the name of the BSDF file,
1126 which is found in the usual auxiliary locations. The
1127 following three string parameters name variables for an
1128 &quot;up&quot; vector, which together with the surface
1129 normal, define the local coordinate system that orients the
1130 BSDF. These variables, along with the thickness, are defined
1131 in a function file given as the next string argument. An
1132 optional transform is used to scale the thickness and
1133 reorient the up vector.
1134 <p>
1135 If no real arguments are given, the BSDF is used by itself
1136 to determine reflection and transmission. If there are at
1137 least 3 real arguments, the first triplet is an additional
1138 diffuse reflectance for the front side. At least 6 real
1139 arguments adds diffuse reflectance to the rear side of the
1140 surface. If there are 9 real arguments, the final triplet
1141 will be taken as an additional diffuse transmittance. All
1142 diffuse components as well as the non-diffuse transmission
1143 are modified by patterns applied to this material. The
1144 non-diffuse reflection from either side are unaffected.
1145 Textures perturb the effective surface normal in the usual
1146 way.
1147 <p>
1148 The surface normal of this type is not altered to face the
1149 incoming ray, so the front and back BSDF reflections may
1150 differ. (Transmission is identical front-to-back by physical
1151 law.) If back visibility is turned off during rendering and
1152 there is no transmission or back-side reflection, only then
1153 the surface will be invisible from behind. Unlike other
1154 data-driven material types, the BSDF type is fully supported
1155 and all parts of the distribution are properly sampled.
1156 <p>
1157
1158 <dt>
1159 <a NAME="aBSDF">
1160 <b>aBSDF</b>
1161 </a>
1162
1163 <dd>
1164 The aBSDF material is identical to the BSDF type with two
1165 important differences. First, proxy geometry is not
1166 supported, so there is no thickness parameter. Second, an
1167 aBSDF is assumed to have some specular through component
1168 (the &rsquo;a&rsquo; stands for &quot;aperture&quot;),
1169 which is treated specially during the direct calculation
1170 and when viewing the material. Based on the BSDF data, the
1171 coefficient of specular transmission is determined and used
1172 for modifying unscattered shadow and view rays.
1173
1174 <pre>
1175 mod aBSDF id
1176 5+ BSDFfile ux uy uz funcfile transform
1177 0
1178 0|3|6|9
1179 rfdif gfdif bfdif
1180 rbdif gbdif bbdif
1181 rtdif gtdif btdif
1182 </pre>
1183
1184 <p>
1185 If a material has no specular transmitted component, it is
1186 much better to use the BSDF type with a zero thickness
1187 than to use aBSDF.
1188 <p>
1189
1190 <dt>
1191 <a NAME="Antimatter">
1192 <b>Antimatter</b>
1193 </a>
1194
1195 <dd>
1196 Antimatter is a material that can &quot;subtract&quot; volumes from other volumes.
1197 A ray passing into an antimatter object becomes blind to all the specified modifiers:
1198
1199 <pre>
1200 mod antimatter id
1201 N mod1 mod2 .. modN
1202 0
1203 0
1204 </pre>
1205
1206 The first modifier will also be used to shade the area leaving the antimatter volume and entering the regular volume.
1207 If mod1 is void, the antimatter volume is completely invisible.
1208 Antimatter does not work properly with the material type <a HREF="#Trans">&quot;trans&quot;</a>,
1209 and multiple antimatter surfaces should be disjoint.
1210 The viewpoint must be outside all volumes concerned for a correct rendering.
1211
1212 </dl>
1213
1214 <p>
1215 <hr>
1216
1217 <h4>
1218 <a NAME="Textures">2.1.3. Textures</a>
1219 </h4>
1220
1221 A texture is a perturbation of the surface normal, and is given by either a function or data.
1222
1223 <p>
1224
1225 <dl>
1226
1227 <dt>
1228 <a NAME="Texfunc">
1229 <b>Texfunc</b>
1230 </a>
1231
1232 <dd>
1233 A texfunc uses an auxiliary function file to specify a procedural texture:
1234
1235 <pre>
1236 mod texfunc id
1237 4+ xpert ypert zpert funcfile transform
1238 0
1239 n A1 A2 .. An
1240 </pre>
1241
1242 <p>
1243
1244 <dt>
1245 <a NAME="Texdata">
1246 <b>Texdata</b>
1247 </a>
1248
1249 <dd>
1250 A texdata texture uses three data files to get the surface normal perturbations.
1251 The variables xfunc, yfunc and zfunc take three arguments each from the interpolated values in xdfname, ydfname and zdfname.
1252
1253 <pre>
1254 mod texdata id
1255 8+ xfunc yfunc zfunc xdfname ydfname zdfname vfname x0 x1 .. xf
1256 0
1257 n A1 A2 .. An
1258 </pre>
1259
1260 </dl>
1261
1262 <p>
1263 <hr>
1264
1265 <h4>
1266 <a NAME="Patterns">2.1.4. Patterns</a>
1267 </h4>
1268
1269 Patterns are used to modify the reflectance of materials. The basic types are given below.
1270
1271 <p>
1272
1273 <dl>
1274
1275 <dt>
1276 <a NAME="Colorfunc">
1277 <b>Colorfunc</b>
1278 </a>
1279
1280 <dd>
1281 A colorfunc is a procedurally defined color pattern. It is specified as follows:
1282
1283 <pre>
1284 mod colorfunc id
1285 4+ red green blue funcfile transform
1286 0
1287 n A1 A2 .. An
1288 </pre>
1289
1290 <p>
1291
1292 <dt>
1293 <a NAME="Brightfunc">
1294 <b>Brightfunc</b>
1295 </a>
1296
1297 <dd>
1298 A brightfunc is the same as a colorfunc, except it is monochromatic.
1299
1300 <pre>
1301 mod brightfunc id
1302 2+ refl funcfile transform
1303 0
1304 n A1 A2 .. An
1305 </pre>
1306
1307 <p>
1308
1309 <dt>
1310 <a NAME="Colordata">
1311 <b>Colordata</b>
1312 </a>
1313
1314 <dd>
1315 Colordata uses an interpolated data map to modify a material's color.
1316 The map is n-dimensional, and is stored in three auxiliary files, one for each color.
1317 The coordinates used to look up and interpolate the data are defined in another auxiliary file.
1318 The interpolated data values are modified by functions of one or three variables.
1319 If the functions are of one variable, then they are passed the corresponding color component (red or green or blue).
1320 If the functions are of three variables, then they are passed the original red, green, and blue values as parameters.
1321
1322 <pre>
1323 mod colordata id
1324 7+n+
1325 rfunc gfunc bfunc rdatafile gdatafile bdatafile
1326 funcfile x1 x2 .. xn transform
1327 0
1328 m A1 A2 .. Am
1329 </pre>
1330
1331 <p>
1332
1333 <dt>
1334 <a NAME="Brightdata">
1335 <b>Brightdata</b>
1336 </a>
1337
1338 <dd>
1339 Brightdata is like colordata, except monochromatic.
1340
1341 <pre>
1342 mod brightdata id
1343 3+n+
1344 func datafile
1345 funcfile x1 x2 .. xn transform
1346 0
1347 m A1 A2 .. Am
1348 </pre>
1349
1350 <p>
1351
1352 <dt>
1353 <a NAME="Colorpict">
1354 <b>Colorpict</b>
1355 </a>
1356
1357 <dd>
1358 Colorpict is a special case of colordata, where the pattern is a two-dimensional image stored in the RADIANCE picture format.
1359 The dimensions of the image data are determined by the picture such that the smaller dimension is always 1,
1360 and the other is the ratio between the larger and the smaller.
1361 For example, a 500x338 picture would have coordinates (u,v) in the rectangle between (0,0) and (1.48,1).
1362
1363 <pre>
1364 mod colorpict id
1365 7+
1366 rfunc gfunc bfunc pictfile
1367 funcfile u v transform
1368 0
1369 m A1 A2 .. Am
1370 </pre>
1371
1372 <p>
1373
1374 <dt>
1375 <a NAME="Colortext">
1376 <b>Colortext</b>
1377 </a>
1378
1379 <dd>
1380 Colortext is dichromatic writing in a polygonal font.
1381 The font is defined in an auxiliary file, such as helvet.fnt.
1382 The text itself is also specified in a separate file, or can be part of the material arguments.
1383 The character size, orientation, aspect ratio and slant is determined by right and down motion vectors.
1384 The upper left origin for the text block as well as the foreground and background colors must also be given.
1385
1386 <pre>
1387 mod colortext id
1388 2 fontfile textfile
1389 0
1390 15+
1391 Ox Oy Oz
1392 Rx Ry Rz
1393 Dx Dy Dz
1394 rfore gfore bfore
1395 rback gback bback
1396 [spacing]
1397 </pre>
1398
1399 or:
1400
1401 <pre>
1402 mod colortext id
1403 2+N fontfile . This is a line with N words ...
1404 0
1405 15+
1406 Ox Oy Oz
1407 Rx Ry Rz
1408 Dx Dy Dz
1409 rfore gfore bfore
1410 rback gback bback
1411 [spacing]
1412 </pre>
1413
1414 <p>
1415
1416 <dt>
1417 <a NAME="Brighttext">
1418 <b>Brighttext</b>
1419 </a>
1420
1421 <dd>
1422 Brighttext is like colortext, but the writing is monochromatic.
1423
1424 <pre>
1425 mod brighttext id
1426 2 fontfile textfile
1427 0
1428 11+
1429 Ox Oy Oz
1430 Rx Ry Rz
1431 Dx Dy Dz
1432 foreground background
1433 [spacing]
1434 </pre>
1435
1436 or:
1437
1438 <pre>
1439 mod brighttext id
1440 2+N fontfile . This is a line with N words ...
1441 0
1442 11+
1443 Ox Oy Oz
1444 Rx Ry Rz
1445 Dx Dy Dz
1446 foreground background
1447 [spacing]
1448 </pre>
1449
1450 <p>
1451
1452 By default, a uniform spacing algorithm is used that guarantees every character will appear in a precisely determined position.
1453 Unfortunately, such a scheme results in rather unattractive and difficult to read text with most fonts.
1454 The optional spacing value defines the distance between characters for proportional spacing.
1455 A positive value selects a spacing algorithm that preserves right margins and indentation,
1456 but does not provide the ultimate in proportionally spaced text.
1457 A negative value insures that characters are properly spaced, but the placement of words then varies unpredictably.
1458 The choice depends on the relative importance of spacing versus formatting.
1459 When presenting a section of formatted text, a positive spacing value is usually preferred.
1460 A single line of text will often be accompanied by a negative spacing value.
1461 A section of text meant to depict a picture, perhaps using a special purpose font such as hexbit4x1.fnt, calls for uniform spacing.
1462 Reasonable magnitudes for proportional spacing are between 0.1 (for tightly spaced characters) and 0.3 (for wide spacing).
1463
1464 <p>
1465
1466 <dt>
1467 <a NAME="Spectrum">
1468 <b>Spectrum</b>
1469 </a>
1470
1471 <dd>
1472 The spectrum primitive is the most basic type for introducing spectral
1473 color to a material.
1474 Since materials only provide RGB parameters, spectral patterns
1475 are the only way to superimpose wavelength-dependent behavior.
1476
1477 <pre>
1478 mod spectrum id
1479 0
1480 0
1481 5+ nmA nmB s1 s2 .. sN
1482 </pre>
1483
1484 <p>
1485 The first two real arguments indicate the extrema of the
1486 spectral range in nanometers.
1487 Subsequent real values correspond to multipliers at each wavelength.
1488 The nmA wavelength may be greater or less than nmB,
1489 but they may not be equal, and their ordering matches
1490 the order of the spectral values.
1491 A minimum of 3 values must be given, which would act
1492 more or less the same as a constant RGB multiplier.
1493 As with RGB values, spectral quantities normally range between 0
1494 and 1 at each wavelength, or average to 1.0 against a standard
1495 sensitivity functions such as V(lambda).
1496 The best results obtain when the spectral range and number
1497 of samples match rendering options, though resampling will handle
1498 any differences, zero-filling wavelenths outside the nmA to nmB
1499 range.
1500 A warning will be issued if the given wavelength range does not
1501 adequately cover the visible spectrum.
1502
1503 <p>
1504
1505 <dt>
1506 <a NAME="Specfile">
1507 <b>Specfile</b>
1508 </a>
1509
1510 <dd>
1511 The specfile primitive is equivalent to the spectrum type, but
1512 the wavelength range and values are contained in a 1-dimensional
1513 data file.
1514 This may be a more convenient way to specify a spectral color,
1515 especially one corresponding to a standard illuminant such as D65
1516 or a library of measured spectra.
1517
1518 <pre>
1519 mod specfile id
1520 1 datafile
1521 0
1522 0
1523 </pre>
1524
1525 <p>
1526 As with the spectrum type, rendering wavelengths outside the defined
1527 range will be zero-filled.
1528 Unlike the spectrum type, the file may contain non-uniform samples.
1529
1530 <p>
1531
1532 <dt>
1533 <a NAME="Specfunc">
1534 <b>Specfunc</b>
1535 </a>
1536
1537 <dd>
1538 The specfunc primitive offers dynamic control over a spectral
1539 pattern, similar to the colorfunc type.
1540
1541 <pre>
1542 mod specfunc id
1543 2+ sfunc funcfile transform
1544 0
1545 2+ nmA nmB A3 ..
1546 </pre>
1547
1548 <p>
1549 Like the spectrum primitive, the wavelength range is specified
1550 in the first two real arguments, and additional real values are
1551 set in the evaluation context.
1552 This function is fed a wavelenth sample
1553 between nmA and nmB as its only argument,
1554 and it returns the corresponding spectral intensity.
1555
1556 <dt>
1557 <a NAME="Specdata">
1558 <b>Specdata</b>
1559 </a>
1560
1561 <dd>
1562 Specdata is like brightdata and colordata, but with more
1563 than 3 specular samples.
1564
1565 <pre>
1566 mod specdata id
1567 3+n+
1568 func datafile
1569 funcfile x1 x2 .. xn transform
1570 0
1571 m A1 A2 .. Am
1572 </pre>
1573
1574 <p>
1575 The data file must have one more dimension than the coordinate
1576 variable count, as this final dimension corresponds to the covered
1577 spectrum.
1578 The starting and ending wavelengths are specified in "datafile"
1579 as well as the number of spectral samples.
1580 The function "func" will be called with two parameters, the
1581 interpolated spectral value for the current coordinate and the
1582 associated wavelength.
1583 If the spectrum is broken into 12 components, then 12 calls
1584 will be made to "func" for the relevant ray evaluation.
1585
1586 <dt>
1587 <a NAME="Specpict">
1588 <b>Specpict</b>
1589 </a>
1590
1591 <dd>
1592 Specpict is a special case of specdata, where the pattern is
1593 a hyperspectral image stored in the common-exponent file format.
1594 The dimensions of the image data are determined by the picture
1595 just as with the colorpict primitive.
1596
1597 <pre>
1598 mod specpict id
1599 5+
1600 func specfile
1601 funcfile u v transform
1602 0
1603 m A1 A2 .. Am
1604 </pre>
1605
1606 <p>
1607 The function "func" is called with the interpolated pixel value
1608 and the wavelength sample in nanometers, the same as specdata,
1609 with as many calls made as there are components in "specfile".
1610
1611 </dl>
1612
1613 <p>
1614 <hr>
1615
1616 <h4>
1617 <a NAME="Mixtures">2.1.5. Mixtures</a>
1618 </h4>
1619
1620 A mixture is a blend of one or more materials or textures and patterns.
1621 Blended materials should not be light source types or virtual source types.
1622 The basic types are given below.
1623
1624 <p>
1625
1626 <dl>
1627
1628 <dt>
1629 <a NAME="Mixfunc">
1630 <b>Mixfunc</b>
1631 </a>
1632
1633 <dd>
1634 A mixfunc mixes two modifiers procedurally. It is specified as follows:
1635
1636 <pre>
1637 mod mixfunc id
1638 4+ foreground background vname funcfile transform
1639 0
1640 n A1 A2 .. An
1641 </pre>
1642
1643 Foreground and background are modifier names that must be
1644 defined earlier in the scene description.
1645 If one of these is a material, then
1646 the modifier of the mixfunc must be &quot;void&quot;.
1647 (Either the foreground or background modifier may be &quot;void&quot;,
1648 which serves as a form of opacity control when used with a material.)
1649 Vname is the coefficient defined in funcfile that determines the influence of foreground.
1650 The background coefficient is always (1-vname).
1651
1652 <p>
1653
1654 <dt>
1655 <a NAME="Mixdata">
1656 <b>Mixdata</b>
1657 </a>
1658
1659 <dd>
1660 Mixdata combines two modifiers using an auxiliary data file:
1661
1662 <pre>
1663 mod mixdata id
1664 5+n+
1665 foreground background func datafile
1666 funcfile x1 x2 .. xn transform
1667 0
1668 m A1 A2 .. Am
1669 </pre>
1670
1671 <dt>
1672 <a NAME="Mixpict">
1673 <b>Mixpict</b>
1674 </a>
1675
1676 <dd>
1677 Mixpict combines two modifiers based on a picture:
1678
1679 <pre>
1680 mod mixpict id
1681 7+
1682 foreground background func pictfile
1683 funcfile u v transform
1684 0
1685 m A1 A2 .. Am
1686 </pre>
1687
1688 <p>
1689
1690 The mixing coefficient function &quot;func&quot; takes three
1691 arguments, the red, green and blue values
1692 corresponding to the pixel at (u,v).
1693
1694 <p>
1695
1696 <dt>
1697 <a NAME="Mixtext">
1698 <b>Mixtext</b>
1699 </a>
1700
1701 <dd>
1702 Mixtext uses one modifier for the text foreground, and one for the background:
1703
1704 <pre>
1705 mod mixtext id
1706 4 foreground background fontfile textfile
1707 0
1708 9+
1709 Ox Oy Oz
1710 Rx Ry Rz
1711 Dx Dy Dz
1712 [spacing]
1713 </pre>
1714
1715 or:
1716
1717 <pre>
1718 mod mixtext id
1719 4+N
1720 foreground background fontfile .
1721 This is a line with N words ...
1722 0
1723 9+
1724 Ox Oy Oz
1725 Rx Ry Rz
1726 Dx Dy Dz
1727 [spacing]
1728 </pre>
1729
1730 </dl>
1731
1732 <p>
1733 <hr>
1734
1735 <h3>
1736 <a NAME="Auxiliary">2.2. Auxiliary Files</a>
1737 </h3>
1738
1739 Auxiliary files used in <a HREF="#Textures">textures</a> and <a HREF="#Patterns">patterns</a>
1740 are accessed by the programs during image generation.
1741 These files may be located in the working directory, or in a library directory.
1742 The environment variable RAYPATH can be assigned an alternate set of search directories.
1743 Following is a brief description of some common file types.
1744
1745 <p>
1746
1747 <h4>
1748 <a NAME="Function">12.2.1. Function Files</a>
1749 </h4>
1750
1751 A function file contains the definitions of variables, functions and constants used by a primitive.
1752 The transformation that accompanies the file name contains the necessary rotations, translations and scalings
1753 to bring the coordinates of the function file into agreement with the world coordinates.
1754 The transformation specification is the same as for the <a HREF="#Generators">xform</a> command.
1755 An example function file is given below:
1756
1757 <pre>
1758 {
1759 This is a comment, enclosed in curly braces.
1760 {Comments can be nested.}
1761 }
1762 { standard expressions use +,-,*,/,^,(,) }
1763 vname = Ny * func(A1) ;
1764 { constants are defined with a colon }
1765 const : sqrt(PI/2) ;
1766 { user-defined functions add to library }
1767 func(x) = 5 + A1*sin(x/3) ;
1768 { functions may be passed and recursive }
1769 rfunc(f,x) = if(x,f(x),f(-x)*rfunc(f,x+1)) ;
1770 { constant functions may also be defined }
1771 cfunc(x) : 10*x / sqrt(x) ;
1772 </pre>
1773
1774 Many variables and functions are already defined by the program, and they are listed in the file rayinit.cal.
1775 The following variables are particularly important:
1776
1777 <pre>
1778 Dx, Dy, Dz - incident ray direction
1779 Nx, Ny, Nz - surface normal at intersection point
1780 Px, Py, Pz - intersection point
1781 T - distance from start
1782 Ts - single ray (shadow) distance
1783 Rdot - cosine between ray and normal
1784 arg(0) - number of real arguments
1785 arg(i) - i'th real argument
1786 </pre>
1787
1788 For mesh objects, the local surface coordinates are available:
1789
1790 <pre>
1791 Lu, Lv - local (u,v) coordinates
1792 </pre>
1793
1794 For BRDF types, the following variables are defined as well:
1795
1796 <pre>
1797 NxP, NyP, NzP - perturbed surface normal
1798 RdotP - perturbed dot product
1799 CrP, CgP, CbP - perturbed material color
1800 </pre>
1801
1802 A unique context is set up for each file so
1803 that the same variable may appear in different
1804 function files without conflict.
1805 The variables listed above and any others defined in
1806 rayinit.cal are available globally.
1807 If no file is needed by a given primitive because all
1808 the required variables are global,
1809 a period (`.') can be given in place of the file name.
1810 It is also possible to give an expression instead
1811 of a straight variable name in a scene file.
1812 Functions (requiring parameters) must be given
1813 as names and not as expressions.
1814
1815 <p>
1816 Constant expressions are used as an optimization in function files.
1817 They are replaced wherever they occur in an expression by their value.
1818 Constant expressions are evaluated only once, so they must not contain any variables or values that can change,
1819 such as the ray variables Px and Ny or the primitive argument function arg().
1820 All the math library functions such as sqrt() and cos() have the constant attribute,
1821 so they will be replaced by immediate values whenever they are given constant arguments.
1822 Thus, the subexpression cos(PI*sqrt(2)) is immediately replaced by its value, -.266255342,
1823 and does not cause any additional overhead in the calculation.
1824
1825 <p>
1826 It is generally a good idea to define constants and variables before they are referred to in a function file.
1827 Although evaluation does not take place until later, the interpreter does variable scoping and
1828 constant subexpression evaluation based on what it has compiled already.
1829 For example, a variable that is defined globally in rayinit.cal
1830 then referenced in the local context of a function file
1831 cannot subsequently be redefined in the same file
1832 because the compiler has already determined the scope of the referenced variable as global.
1833 To avoid such conflicts, one can state the scope of a variable explicitly by
1834 preceding the variable name with a context mark (a back-quote) for a local variable,
1835 or following the name with a context mark for a global variable.
1836
1837 <p>
1838
1839 <h4>
1840 <a NAME="Data">2.2.2. Data Files</a>
1841 </h4>
1842
1843 Data files contain n-dimensional arrays of real numbers used for interpolation.
1844 Typically, definitions in a function file determine how to index and use interpolated data values.
1845 The basic data file format is as follows:
1846
1847 <pre>
1848 N
1849 beg1 end1 m1
1850 0 0 m2 x2.1 x2.2 x2.3 x2.4 .. x2.m2
1851 ...
1852 begN endN mN
1853 DATA, later dimensions changing faster.
1854 </pre>
1855
1856 N is the number of dimensions.
1857 For each dimension, the beginning and ending coordinate values and the dimension size is given.
1858 Alternatively, individual coordinate values can be given when the points are not evenly spaced.
1859 These values must either be increasing or decreasing monotonically.
1860 The data is m1*m2*...*mN real numbers in ASCII form.
1861 Comments may appear anywhere in the file, beginning with a pound
1862 sign ('#') and continuing to the end of line.
1863
1864 <p>
1865
1866 <h4>
1867 <a NAME="Font">2.2.3. Font Files</a>
1868 </h4>
1869
1870 A font file lists the polygons which make up a character set.
1871 Comments may appear anywhere in the file, beginning with a pound
1872 sign ('#') and continuing to the end of line.
1873 All numbers are decimal integers:
1874
1875 <pre>
1876 code n
1877 x0 y0
1878 x1 y1
1879 ...
1880 xn yn
1881 ...
1882 </pre>
1883
1884 The ASCII codes can appear in any order. N is the number of vertices, and the last is automatically connected to the first.
1885 Separate polygonal sections are joined by coincident sides.
1886 The character coordinate system is a square with lower left corner at (0,0), lower right at (255,0) and upper right at (255,255).
1887
1888 <p>
1889
1890 <hr>
1891
1892 <h3>
1893 <a NAME="Generators">2.3. Generators</a>
1894 </h3>
1895
1896 A generator is any program that produces a scene description as its output.
1897 They usually appear as commands in a scene description file.
1898 An example of a simple generator is genbox.
1899
1900 <ul>
1901
1902 <li>
1903 <a NAME="Genbox" HREF="../man_html/genbox.1.html">
1904 <b>Genbox</b>
1905 </a>
1906 takes the arguments of width, height and depth to produce a parallelepiped description.
1907 <li>
1908 <a NAME="Genprism" HREF="../man_html/genprism.1.html">
1909 <b>Genprism</b>
1910 </a>
1911 takes a list of 2-dimensional coordinates and extrudes them along a vector to
1912 produce a 3-dimensional prism.
1913 <li>
1914 <a NAME="Genrev" HREF="../man_html/genrev.1.html">
1915 <b>Genrev</b>
1916 </a>
1917 is a more sophisticated generator that produces an object of rotation from parametric functions for radius and axis position.
1918 <li>
1919 <a NAME="Gensurf" HREF="../man_html/gensurf.1.html">
1920 <b>Gensurf</b>
1921 </a>
1922 tessellates a surface defined by the parametric functions x(s,t), y(s,t), and z(s,t).
1923 <li>
1924 <a NAME="Genworm" HREF="../man_html/genworm.1.html">
1925 <b>Genworm</b>
1926 </a>
1927 links cylinders and spheres along a curve.
1928 <li>
1929 <a NAME="Gensky" HREF="../man_html/gensky.1.html">
1930 <b>Gensky</b>
1931 </a>
1932 produces a sun and sky distribution corresponding to a given time and date.
1933 <li>
1934 <a NAME="Xform" HREF="../man_html/xform.1.html">
1935 <b>Xform</b>
1936 </a>
1937 is a program that transforms a scene description from one coordinate space to another.
1938 Xform does rotation, translation, scaling, and mirroring.
1939
1940 </ul>
1941
1942 <p>
1943 <hr>
1944
1945 <h2>
1946 <a NAME="Image">3. Image Generation</a>
1947 </h2>
1948
1949 Once the scene has been described in three-dimensions, it is possible to generate a two-dimensional image from a given perspective.
1950
1951 <p>
1952 The image generating programs use an <a NAME="octree"><b>octree</b></a> to efficiently trace rays through the scene.
1953 An octree subdivides space into nested octants which contain sets of surfaces.
1954 In RADIANCE, an octree is created from a scene description by <a NAME="oconv1" HREF="../man_html/oconv.1.html"><b>oconv</b></a>.
1955 The details of this process are not important, but the octree will serve as input to the ray-tracing programs and
1956 directs the use of a scene description.
1957 <ul>
1958 <li>
1959 <a NAME="rvu" HREF="../man_html/rvu.1.html"><b>Rvu</b></a> is ray-tracing program for viewing a scene interactively.
1960 When the user specifies a new perspective, rvu quickly displays a rough image on the terminal,
1961 then progressively increases the resolution as the user looks on.
1962 He can select a particular section of the image to improve, or move to a different view and start over.
1963 This mode of interaction is useful for debugging scenes as well as determining the best view for a final image.
1964
1965 <li>
1966 <a NAME="rpict" HREF="../man_html/rpict.1.html"><b>Rpict</b></a> produces a high-resolution picture of a scene from a particular perspective.
1967 This program features adaptive sampling, crash recovery and progress reporting, all of which are important for time-consuming images.
1968 </ul>
1969 <p>
1970 A number of <a NAME="filters"><b>filters</b></a> are available for manipulating picture files:
1971 <ul>
1972 <li> <a HREF="../man_html/pfilt.1.html"><b>Pfilt</b></a>
1973 sets the exposure and performs antialiasing.
1974 <li> <a HREF="../man_html/pcompos.1.html"><b>Pcompos</b></a>
1975 composites (cuts and pastes) pictures.
1976 <li> <a HREF="../man_html/pcomb.1.html"><b>Pcomb</b></a>
1977 performs arbitrary math on one or more pictures.
1978 <li> <a HREF="../man_html/pcond.1.html"><b>Pcond</b></a>
1979 conditions a picture for a specific display device.
1980 <li> <a HREF="../man_html/protate.1.html"><b>Protate</b></a>
1981 rotates a picture 90 degrees clockwise.
1982 <li> <a HREF="../man_html/pflip.1.html"><b>Pflip</b></a>
1983 flips a picture horizontally, vertically, or both
1984 (180 degree rotation).
1985 <li> <a HREF="../man_html/pvalue.1.html"><b>Pvalue</b></a>
1986 converts a picture to and from simpler formats.
1987 </ul>
1988
1989 <p>
1990 Pictures may be displayed directly under X11 using the program
1991 <a HREF="../man_html/ximage.1.html">ximage</a>,
1992 or converted a standard image format using one of the following
1993 <b>translators</b>:
1994 <ul>
1995 <li> <a HREF="../man_html/ra_bmp.1.html"><b>Ra_bmp</b></a>
1996 converts to and from BMP image format.
1997 <li> <a HREF="../man_html/ra_ppm.1.html"><b>Ra_ppm</b></a>
1998 converts to and from Poskanzer Portable Pixmap formats.
1999 <li> <a HREF="../man_html/ra_ps.1.html"><b>Ra_ps</b></a>
2000 converts to PostScript color and greyscale formats.
2001 <li> <a HREF="../man_html/ra_rgbe.1.html"><b>Ra_rgbe</b></a>
2002 converts to and from Radiance uncompressed picture format.
2003 <li> <a HREF="../man_html/ra_t16.1.html"><b>Ra_t16</b></a>
2004 converts to and from Targa 16 and 24-bit image formats.
2005 <li> <a HREF="../man_html/ra_t8.1.html"><b>Ra_t8</b></a>
2006 converts to and from Targa 8-bit image format.
2007 <li> <a HREF="../man_html/ra_tiff.1.html"><b>Ra_tiff</b></a>
2008 converts to and from TIFF.
2009 <li> <a HREF="../man_html/ra_xyze.1.html"><b>Ra_xyze</b></a>
2010 converts to and from Radiance CIE picture format.
2011 </ul>
2012
2013 <p>
2014
2015 <hr>
2016
2017 <h2>
2018 <a NAME="License">4. License</a>
2019 </h2>
2020
2021 <pre>
2022 The Radiance Software License, Version 1.0
2023
2024 Copyright (c) 1990 - 2021 The Regents of the University of California,
2025 through Lawrence Berkeley National Laboratory. All rights reserved.
2026
2027 Redistribution and use in source and binary forms, with or without
2028 modification, are permitted provided that the following conditions
2029 are met:
2030
2031 1. Redistributions of source code must retain the above copyright
2032 notice, this list of conditions and the following disclaimer.
2033
2034 2. Redistributions in binary form must reproduce the above copyright
2035 notice, this list of conditions and the following disclaimer in
2036 the documentation and/or other materials provided with the
2037 distribution.
2038
2039 3. The end-user documentation included with the redistribution,
2040 if any, must include the following acknowledgment:
2041 &quot;This product includes Radiance software
2042 (<a HREF="http://radsite.lbl.gov/">http://radsite.lbl.gov/</a>)
2043 developed by the Lawrence Berkeley National Laboratory
2044 (<a HREF="http://www.lbl.gov/">http://www.lbl.gov/</a>).&quot;
2045 Alternately, this acknowledgment may appear in the software itself,
2046 if and wherever such third-party acknowledgments normally appear.
2047
2048 4. The names &quot;Radiance,&quot; &quot;Lawrence Berkeley National Laboratory&quot;
2049 and &quot;The Regents of the University of California&quot; must
2050 not be used to endorse or promote products derived from this
2051 software without prior written permission. For written
2052 permission, please contact [email protected].
2053
2054 5. Products derived from this software may not be called &quot;Radiance&quot;,
2055 nor may &quot;Radiance&quot; appear in their name, without prior written
2056 permission of Lawrence Berkeley National Laboratory.
2057
2058 THIS SOFTWARE IS PROVIDED ``AS IS&quot; AND ANY EXPRESSED OR IMPLIED
2059 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
2060 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
2061 DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
2062 ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
2063 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
2064 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
2065 USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
2066 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
2067 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
2068 OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
2069 SUCH DAMAGE.
2070 </pre>
2071
2072 <hr>
2073
2074 <h2>
2075 <a NAME="Ack">5. Acknowledgements</a>
2076 </h2>
2077
2078 This work was supported by the Assistant Secretary of Conservation and Renewable Energy,
2079 Office of Building Energy Research and Development,
2080 Buildings Equipment Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.
2081
2082 <p>
2083 Additional work was sponsored by the Swiss federal government
2084 under the Swiss LUMEN Project and was carried out in the
2085 Laboratoire d'Energie Solaire (LESO Group) at the
2086 Ecole Polytechnique Federale de Lausanne (EPFL University) in Lausanne, Switzerland.
2087
2088 <p>
2089
2090 <hr>
2091
2092 <h2>
2093 <a NAME="Ref">6.</a> References
2094 </h2>
2095 <p>
2096 <ul>
2097 <li>Ward, Gregory J., Bruno Bueno, David Geisler-Moroder,
2098 Lars O. Grobe, Jacob C. Jonsson, Eleanor
2099 S. Lee, Taoning Wang, Helen Rose Wilson,
2100 &quot;<a href="https://doi.org/10.1016/j.enbuild.2022.111890">Daylight
2101 Simulation Workflows Incorporating Measured Bidirectional
2102 Scattering Distribution Functions</a>&quot;
2103 <em>Energy &amp; Buildings</em>, Vol. 259, No. 11890, 2022.
2104 <li>Wang, Taoning, Gregory Ward, Eleanor Lee,
2105 &quot;<a href="https://authors.elsevier.com/a/1XQ0a1M7zGwT7v">Efficient
2106 modeling of optically-complex, non-coplanar exterior shading:
2107 Validation of matrix algebraic methods</a>&quot;
2108 <em>Energy & Buildings</em>, vol. 174, pp. 464-83, Sept. 2018.
2109 <li>Lee, Eleanor S., David Geisler-Moroder, Gregory Ward,
2110 &quot;<a href="https://eta.lbl.gov/sites/default/files/publications/solar_energy.pdf">Modeling
2111 the direct sun component in buildings using matrix
2112 algebraic approaches: Methods and
2113 validation</a>,&quot; <em>Solar Energy</em>,
2114 vol. 160, 15 January 2018, pp 380-395.
2115 <li>Narain, Rahul, Rachel A. Albert, Abdullah Bulbul,
2116 Gregory J. Ward, Marty Banks, James F. O'Brien,
2117 &quot;<a href="http://graphics.berkeley.edu/papers/Narain-OPI-2015-08/index.html">Optimal
2118 Presentation of Imagery with Focus
2119 Cues on Multi-Plane Displays</a>,&quot;
2120 <em>SIGGRAPH 2015</em>.
2121 <li>Ward, Greg, Murat Kurt, and Nicolas Bonneel,
2122 &quot;<a href="papers/WMAM14_Tensor_Tree_Representation.pdf">Reducing
2123 Anisotropic BSDF Measurement to Common Practice</a>,&quot;
2124 <em>Workshop on Material Appearance Modeling</em>, 2014.
2125 <li>Banks, Martin, Abdullah Bulbul, Rachel Albert, Rahul Narain,
2126 James F. O'Brien, Gregory Ward,
2127 &quot;<a href="http://graphics.berkeley.edu/papers/Banks-TPO-2014-05/index.html">The
2128 Perception of Surface Material from Disparity and Focus Cues</a>,&quot;
2129 <em>VSS 2014</em>.
2130 <li>McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee,
2131 &quot;<a href="http://gaia.lbl.gov/btech/papers/4414.pdf">
2132 A validation of a ray-tracing tool used to generate
2133 bi-directional scattering distribution functions for
2134 complex fenestration systems</a>,&quot;
2135 <em>Solar Energy</em>, 98, 404-14,
2136 November 2013.
2137 <li>Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson,
2138 &quot;<a href="http://gaia.lbl.gov/btech/papers/4414.pdf">Simulating
2139 the Daylight Performance of Complex Fenestration Systems
2140 Using Bidirectional Scattering Distribution Functions within
2141 Radiance</a>,&quot;
2142 <em>Leukos</em>, 7(4)
2143 April 2011.
2144 <li>Cater, Kirsten, Alan Chalmers, Greg Ward,
2145 &quot;<a href="http://www.anyhere.com/gward/papers/egsr2003.pdf">Detail to Attention:
2146 Exploiting Visual Tasks for Selective Rendering</a>,&quot;
2147 <em>Eurographics Symposium
2148 on Rendering 2003</em>, June 2003.
2149 <li>Ward, Greg, Elena Eydelberg-Vileshin,
2150 &quot;<a HREF="http://www.anyhere.com/gward/papers/egwr02/index.html">Picture Perfect RGB
2151 Rendering Using Spectral Prefiltering and Sharp Color Primaries</a>,&quot;
2152 Thirteenth Eurographics Workshop on Rendering (2002),
2153 P. Debevec and S. Gibson (Editors), June 2002.
2154 <li>Ward, Gregory,
2155 &quot;<a HREF="http://www.anyhere.com/gward/papers/cic01.pdf">High Dynamic Range Imaging</a>,&quot;
2156 Proceedings of the Ninth Color Imaging Conference, November 2001.
2157 <li>Ward, Gregory and Maryann Simmons,
2158 &quot;<a HREF="http://www.anyhere.com/gward/papers/tog99.pdf">
2159 The Holodeck Ray Cache: An Interactive Rendering System for Global Illumination in Nondiffuse
2160 Environments</a>,&quot; ACM Transactions on Graphics, 18(4):361-98, October 1999.
2161 <li>Larson, G.W., &quot;<a HREF="http://www.anyhere.com/gward/papers/ewp98.pdf">The Holodeck: A Parallel
2162 Ray-caching Rendering System</a>,&quot; Proceedings of the Second
2163 Eurographics Workshop on Parallel Graphics and Visualisation,
2164 September 1998.
2165 <li>Larson, G.W. and R.A. Shakespeare,
2166 <a HREF="http://radsite.lbl.gov/radiance/book/index.html"><em>Rendering with Radiance:
2167 the Art and Science of Lighting Visualization</em></a>,
2168 Morgan Kaufmann Publishers, 1998.
2169 <li>Larson, G.W., H. Rushmeier, C. Piatko,
2170 &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/lbnl39882/tonemap.pdf">A Visibility
2171 Matching Tone Reproduction Operator for
2172 High Dynamic Range Scenes</a>,&quot; LBNL Technical Report 39882,
2173 January 1997.
2174 <li>Ward, G., &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/erw95.1/paper.html">Making
2175 Global Illumination User-Friendly</a>,&quot; Sixth
2176 Eurographics Workshop on Rendering, Springer-Verlag,
2177 Dublin, Ireland, June 1995.</li>
2178 <li>Rushmeier, H., G. Ward, C. Piatko, P. Sanders, B. Rust,
2179 &quot;<a HREF="http://radsite.lbl.gov/mgf/compare.html">
2180 Comparing Real and Synthetic Images: Some Ideas about
2181 Metrics</a>,&quot; Sixth Eurographics Workshop on Rendering,
2182 Springer-Verlag, Dublin, Ireland, June 1995.</li>
2183 <li>Ward, G., &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/sg94.1/paper.html">The RADIANCE
2184 Lighting Simulation and Rendering System</a>,&quot; <em>Computer
2185 Graphics</em>, July 1994.</li>
2186 <li>Rushmeier, H., G. Ward, &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/sg94.2/energy.html">Energy
2187 Preserving Non-Linear Filters</a>,&quot; <em>Computer
2188 Graphics</em>, July 1994.</li>
2189 <li>Ward, G., &quot;A Contrast-Based Scalefactor for Luminance
2190 Display,&quot; <em>Graphics Gems IV</em>, Edited by Paul Heckbert,
2191 Academic Press 1994.</li>
2192 <li>Ward, G., &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/sg92/paper.html">Measuring and
2193 Modeling Anisotropic Reflection</a>,&quot; <em>Computer
2194 Graphics</em>, Vol. 26, No. 2, July 1992. </li>
2195 <li>Ward, G., P. Heckbert, &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/erw92/paper.html">Irradiance
2196 Gradients</a>,&quot; Third Annual Eurographics Workshop on
2197 Rendering, Springer-Verlag, May 1992. </li>
2198 <li>Ward, G., &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/erw91/erw91.html">Adaptive Shadow
2199 Testing for Ray Tracing</a>&quot; Photorealistic Rendering in
2200 Computer Graphics, proceedings of 1991 Eurographics
2201 Rendering Workshop, edited by P. Brunet and F.W. Jansen,
2202 Springer-Verlag. </li>
2203 <li>Ward, G., &quot;Visualization,&quot; <em>Lighting Design and
2204 Application</em>, Vol. 20, No. 6, June 1990. </li>
2205 <li>Ward, G., F. Rubinstein, R. Clear, &quot;<a HREF="http://radsite.lbl.gov/radiance/papers/sg88/paper.html">A Ray Tracing Solution for
2206 Diffuse Interreflection</a>,&quot; <em>Computer Graphics</em>,
2207 Vol. 22, No. 4, August 1988. </li>
2208 <li>Ward, G., F. Rubinstein, &quot;A New Technique for Computer
2209 Simulation of Illuminated Spaces,&quot; <em>Journal of the
2210 Illuminating Engineering Society</em>, Vol. 17, No. 1,
2211 Winter 1988. </li>
2212 </ul>
2213 <p>
2214 See the <a HREF="index.html">RADIANCE Reference Materials</a> page
2215 for additional information.
2216 <hr>
2217
2218 <a NAME="Index"><h2>7. Types Index</h2></a>
2219
2220 <pre>
2221 <h4>
2222 SURFACES MATERIALS TEXTURES PATTERNS MIXTURES</h4>
2223 <a HREF="#Source">Source</a> <a HREF="#Light">Light</a> <a HREF="#Texfunc">Texfunc</a> <a HREF="#Colorfunc">Colorfunc</a> <a HREF="#Mixfunc">Mixfunc</a>
2224 <a HREF="#Sphere">Sphere</a> <a HREF="#Illum">Illum</a> <a HREF="#Texdata">Texdata</a> <a HREF="#Brightfunc">Brightfunc</a> <a HREF="#Mixdata">Mixdata</a>
2225 <a HREF="#Bubble">Bubble</a> <a HREF="#Glow">Glow</a> <a HREF="#Colordata">Colordata</a> <a HREF="#Mixtext">Mixtext</a>
2226 <a HREF="#Polygon">Polygon</a> <a HREF="#Spotlight">Spotlight</a> <a HREF="#Brightdata">Brightdata</a>
2227 <a HREF="#Cone">Cone</a> <a HREF="#Mirror">Mirror</a> <a HREF="#Colorpict">Colorpict</a>
2228 <a HREF="#Cup">Cup</a> <a HREF="#Prism1">Prism1</a> <a HREF="#Colortext">Colortext</a>
2229 <a HREF="#Cylinder">Cylinder</a> <a HREF="#Prism2">Prism2</a> <a HREF="#Brighttext">Brighttext</a>
2230 <a HREF="#Tube">Tube</a> <a HREF="#Plastic">Plastic</a>
2231 <a HREF="#Ring">Ring</a> <a HREF="#Metal">Metal</a>
2232 <a HREF="#Instance">Instance</a> <a HREF="#Trans">Trans</a>
2233 <a HREF="#Mesh">Mesh</a> <a HREF="#Plastic2">Plastic2</a>
2234 <a HREF="#Metal2">Metal2</a>
2235 <a HREF="#Trans2">Trans2</a>
2236 <a HREF="#Mist">Mist</a>
2237 <a HREF="#Dielectric">Dielectric</a>
2238 <a HREF="#Interface">Interface</a>
2239 <a HREF="#Glass">Glass</a>
2240 <a HREF="#Plasfunc">Plasfunc</a>
2241 <a HREF="#Metfunc">Metfunc</a>
2242 <a HREF="#Transfunc">Transfunc</a>
2243 <a HREF="#BRTDfunc">BRTDfunc</a>
2244 <a HREF="#Plasdata">Plasdata</a>
2245 <a HREF="#Metdata">Metdata</a>
2246 <a HREF="#Transdata">Transdata</a>
2247 <a HREF="#BSDF">BSDF</a>
2248 <a HREF="#Antimatter">Antimatter</a>
2249
2250 </pre>
2251
2252 <p>
2253
2254
2255 <hr>
2256 <center>Last Update: October 22, 1997</center>
2257 </body>
2258 </html>
2259