| 1 |
|
<html> |
| 2 |
|
<head> |
| 3 |
|
<title> |
| 4 |
< |
The RADIANCE 4.0 Synthetic Imaging System |
| 4 |
> |
The RADIANCE 4.1 Synthetic Imaging System |
| 5 |
|
</title> |
| 6 |
|
</head> |
| 7 |
|
<body> |
| 9 |
|
<p> |
| 10 |
|
|
| 11 |
|
<h1> |
| 12 |
< |
The RADIANCE 4.0 Synthetic Imaging System |
| 12 |
> |
The RADIANCE 4.1 Synthetic Imaging System |
| 13 |
|
</h1> |
| 14 |
|
|
| 15 |
|
<p> |
| 1053 |
|
<p> |
| 1054 |
|
|
| 1055 |
|
<dt> |
| 1056 |
+ |
<a NAME="BSDF"> |
| 1057 |
+ |
<b>BSDF</b> |
| 1058 |
+ |
</a> |
| 1059 |
+ |
|
| 1060 |
+ |
<dd> |
| 1061 |
+ |
The BSDF material type loads an XML (eXtensible Markup Language) |
| 1062 |
+ |
file describing a bidirectional scattering distribution function. |
| 1063 |
+ |
Real arguments to this material may define additional |
| 1064 |
+ |
diffuse components that augment the BSDF data. |
| 1065 |
+ |
String arguments are used to define thickness for proxied |
| 1066 |
+ |
surfaces and the "up" orientation for the material. |
| 1067 |
+ |
|
| 1068 |
+ |
<pre> |
| 1069 |
+ |
mod BSDF id |
| 1070 |
+ |
6+ thick BSDFfile ux uy uz funcfile transform |
| 1071 |
+ |
0 |
| 1072 |
+ |
0|3|6|9 |
| 1073 |
+ |
rfdif gfdif bfdif |
| 1074 |
+ |
rbdif gbdif bbdif |
| 1075 |
+ |
rtdif gtdif btdif |
| 1076 |
+ |
</pre> |
| 1077 |
+ |
|
| 1078 |
+ |
<p> |
| 1079 |
+ |
The first string argument is a "thickness" parameter that may be used |
| 1080 |
+ |
to hide detail geometry being proxied by an aggregate BSDF material. |
| 1081 |
+ |
If a view or shadow ray hits a BSDF proxy with non-zero thickness, |
| 1082 |
+ |
it will pass directly through as if the surface were not there. |
| 1083 |
+ |
Similar to the illum type, this permits direct viewing and |
| 1084 |
+ |
shadow testing of complex geometry. |
| 1085 |
+ |
The BSDF is used when a scattered (indirect) ray hits the surface, |
| 1086 |
+ |
and any transmitted sample rays will be offset by the thickness amount |
| 1087 |
+ |
to avoid the hidden geometry and gather samples from the other side. |
| 1088 |
+ |
In this manner, BSDF surfaces can improve the results for indirect |
| 1089 |
+ |
scattering from complex systems without sacrificing appearance or |
| 1090 |
+ |
shadow accuracy. |
| 1091 |
+ |
If the BSDF has transmission and back-side reflection data, |
| 1092 |
+ |
a parallel BSDF surface may be |
| 1093 |
+ |
placed slightly less than the given thickness away from the front surface |
| 1094 |
+ |
to enclose the complex geometry on both sides. |
| 1095 |
+ |
The sign of the thickness is important, as it indicates |
| 1096 |
+ |
whether the proxied geometry is behind the <emph>BSDF</emph> |
| 1097 |
+ |
surface (when thickness is positive) or in front (when |
| 1098 |
+ |
thickness is negative). |
| 1099 |
+ |
<p> |
| 1100 |
+ |
The second string argument is the name of the BSDF file, |
| 1101 |
+ |
which is found in the usual auxiliary locations. The |
| 1102 |
+ |
following three string parameters name variables for an |
| 1103 |
+ |
"up" vector, which together with the surface |
| 1104 |
+ |
normal, define the local coordinate system that orients the |
| 1105 |
+ |
BSDF. These variables, along with the thickness, are defined |
| 1106 |
+ |
in a function file given as the next string argument. An |
| 1107 |
+ |
optional transform is used to scale the thickness and |
| 1108 |
+ |
reorient the up vector. |
| 1109 |
+ |
<p> |
| 1110 |
+ |
If no real arguments are given, the BSDF is used by itself |
| 1111 |
+ |
to determine reflection and transmission. If there are at |
| 1112 |
+ |
least 3 real arguments, the first triplet is an additional |
| 1113 |
+ |
diffuse reflectance for the front side. At least 6 real |
| 1114 |
+ |
arguments adds diffuse reflectance to the rear side of the |
| 1115 |
+ |
surface. If there are 9 real arguments, the final triplet |
| 1116 |
+ |
will be taken as an additional diffuse transmittance. All |
| 1117 |
+ |
diffuse components as well as the non-diffuse transmission |
| 1118 |
+ |
are modified by patterns applied to this material. The |
| 1119 |
+ |
non-diffuse reflection from either side are unaffected. |
| 1120 |
+ |
Textures perturb the effective surface normal in the usual |
| 1121 |
+ |
way. |
| 1122 |
+ |
<p> |
| 1123 |
+ |
The surface normal of this type is not altered to face the |
| 1124 |
+ |
incoming ray, so the front and back BSDF reflections may |
| 1125 |
+ |
differ. (Transmission is identical front-to-back by physical |
| 1126 |
+ |
law.) If back visibility is turned off during rendering and |
| 1127 |
+ |
there is no transmission or back-side reflection, only then |
| 1128 |
+ |
the surface will be invisible from behind. Unlike other |
| 1129 |
+ |
data-driven material types, the BSDF type is fully supported |
| 1130 |
+ |
and all parts of the distribution are properly sampled. |
| 1131 |
+ |
<p> |
| 1132 |
+ |
|
| 1133 |
+ |
<dt> |
| 1134 |
|
<a NAME="Antimatter"> |
| 1135 |
|
<b>Antimatter</b> |
| 1136 |
|
</a> |
| 1999 |
|
<a HREF="#Plasdata">Plasdata</a> |
| 2000 |
|
<a HREF="#Metdata">Metdata</a> |
| 2001 |
|
<a HREF="#Transdata">Transdata</a> |
| 2002 |
+ |
<a HREF="#BSDF">BSDF</a> |
| 2003 |
|
<a HREF="#Antimatter">Antimatter</a> |
| 2004 |
|
|
| 2005 |
|
</pre> |
