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Commonly referred RSL, '''Renderman Shading Language''' (abbreviated RSL) is useda tocomponent defineof shadersthe [[RenderMan Interface Specification]], and is used into define [[RenderManshader]]s. The language syntax is [[C (programming language)|C-like]].
TheA beautyshader ofwritten usingin aRSL standardcan languagebe isused thatwithout achanges programmedon shaderany canRenderMan-compliant berenderer, usedsuch in multiple renders, beas itPixar's [[PhotoRealistic RenderMan]], DNA Research 's [[3Delight ]], Sitexgraphics ' Air or an open source solution such as [[Pixie (renderer)|Pixie]] or [[Aqsis]]. ▼[[Pixar]] has set a standard in the Shading Language.
▲The beauty of using a standard language is that a programmed shader can be used in multiple renders, be it [[PhotoRealistic RenderMan]], DNA Research 3Delight, Sitexgraphics Air or an open source solution such as [[Pixie (renderer)|Pixie]] or [[Aqsis]].
RenderMan Shading Language defines standalone functions and five types of shaders: surface, light, volume, imager and displacement shaders.
An example of a surface shader that defines a metal surface is:
<syntaxhighlight lang="c">
surface metal (float Ka = 1; float Ks = 1; float roughness = 0.1;)
{
{
normal Nf = faceforward(normalize(N), I);
normal vector VNf = -faceforward (normalize(N), I);
vector OiV = Os- normalize (I);
Oi = Os;
Ci = Os * Cs * (Ka * ambient() + Ks * specular (Nf, V, roughness));
}
</syntaxhighlight>
Shaders doexpress thetheir work by reading and writing special variables likesuch as Cs - (surface color), N - (normal at given point), and Ci - (final surface color).
The arguments to the shaders are global parameters that are attached to objects of the model (so one metal shader can be used for different metals and so on). Shaders have no return values, but functions can be defined which take arguments and return a value. For example, the following function computes vector length using the [[dot product]] operator ".":
<syntaxhighlight lang="c">
and they have no return values. On the other hand functions operate by taking arguments and returning a value, and make little use of special variables. For example the following function computes vector length and looks almost like a [[Java (programming language)|Java]] or [[C (programming language)|C]] function, except for using the [[dot product]] operator:
float length (vector v) {
return sqrt (v . v); /* . is a [[dot product]] */
}
</syntaxhighlight>
==Further reading==
*[[Steve {{cite book | last=Upstill]]: ''| first=Steve | title=The RenderMan Companioncompanion : Aa Programmerprogrammer's Guideguide to Realisticrealistic Computercomputer Graphics'',graphics | publisher=Addison-Wesley | ___location=Reading, ISBNMass | year=1990 | isbn=0-201-50868-0 | url=https://archive.org/details/rendermancompani00upst }}
*[[Anthony {{cite book | last=Apodaca | first=Anthony A.| authorlink=Anthony Apodaca]], [[Larry| last2=Gritz]]: ''| first2=Larry | title=Advanced RenderMan : Creatingcreating CGI for Motionmotion Pictures'',pictures | publisher=Morgan Kaufmann Publishers,| ISBN___location=San Francisco | year=1999 | isbn=1-55860-618-1 | url=https://archive.org/details/advancedrenderma00apod_0 }}
* {{cite book | last=Cortes | first=Rudy | last2=Raghavachary |first2=Saty | title=The RenderMan shading language guide | publisher=Thomson Course Technology | ___location=Boston, Mass | year=2008 | isbn=1-59863-286-8 }}
*[[Ian Stephenson]]: ''Essential RenderMan Fast'', Springer, ISBN 1-85233-608-0
*[[Saty Raghavachary]]: ''Rendering for Beginners: Image synthesis using RenderMan'', Focal Press, ISBN 0-240-51935-3
*[[Rudy Cortes and Saty Raghavachary]]: ''The RenderMan Shading Language Guide'', Course Technology PTR, 1 edition (March 28, 2007), ISBN 1-598-63286-8
==External links==
[[Category:3D graphics software]]
* [https://renderman.pixar.com/resources/RenderMan_20/shadingLanguage.html Shading Language (RSL) documentation]
[[Category:3D computer graphics]]
{{RenderMan}}
{{DEFAULTSORT:Renderman Shading Language}}
{{graphics-software-stub}}
▲[[Category: PixarRenderMan]]
[[Category:Shading languages]]
[[zh:RenderMan规范#RenderMan着色语言（RSL）]]
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