RenderMan & RISpec, "Surface" calls in light shaders

comp.graphics.rendering.renderman - RenderMan interface & shading language.


RenderMan & RISpec >> "Surface" calls in light shaders

by STefano » Wed, 04 Oct 2006 00:26:03 GMT

Hi all , does something like this have any sense ?

code:
light
surfLight(
float intensity = 1;
color lightcolor = 1;
point from = point "shader" (0,0,0);
)
{
illuminate(from) {
color surfaceCol ;
float getme = surface( "_diffuse" , surfaceCol );
printf ( "%f %c \n", getme , surfaceCol ) ;
Cl += surfaceCol; // it should look twice as bright
}
}



It seems like i get nothing returning from the

code:
surface( "_diffuse" , surfaceCol )

call (the _diffuse component is an output color of a surface shader)?
Thanks ,
STe

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RenderMan & RISpec >> "Surface" calls in light shaders

by georgeharker@googlemail.com » Wed, 04 Oct 2006 16:48:22 GMT


The question is, when does _diffuse get output from the surface shader.
It will have some default value as specified in the parameter list of
the surface shader, but to be useful the surface shader has to assign
something to it.

My guess given that it is called _diffuse would be that it is the
result of running the lighting and combining with the local shading
model - and is therefore computed after the call which invokes lighting
(illuminance, diffuse() etc). In which case, when the lighting is
invoked, that variable most probably hasn't been set yet, and you won't
get anything useful from it.

Cheers

George
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