Renderman Volume Shaders

#1

In the application notes there is a documentation regarding the smoke shader… there is also a slim template of it. Problem is that right off the shelf the renders dont look great.
My concerns are as follows:-
a) given a geometry what kind of noise is suitable for volumetrics? Does one just simply use the turb or bownians provided or there is something more?
b) in the slim node provided what optimisations must be added to do stuff like self shadowing? Does one need to append an illumination loop into the already provided smoke shader?
c) for shadow maps; doesnt the deep shadow map need to have information of the inside volume will look like do run the illumination loops on? say I have a sphere in the deep shadow map it would be a sphere, but shouldnt it be like the same noise as in the volume shader?
Also and tips and advice on how to pull off volume shaders would really help.
thanks in advance

#2

Use whatever noise you want. It can fractal, turbulence, value, distortion, multifractal, etc…

b) in the slim node provided what optimisations must be added to do stuff like self shadowing?

You probably have to do your own by either using the deep shadow map or ray-stepping down your own shadow ray.

Does one need to append an illumination loop into the already provided smoke shader?

If you want illumination, I would assume so.

c) for shadow maps; doesnt the deep shadow map need to have information of the inside volume will look like do run the illumination loops on? say I have a sphere in the deep shadow map it would be a sphere, but shouldnt it be like the same noise as in the volume shader?

You want the deep shadow map to use the same noise function when it’s building up. It computes it’s function based on the location of the light. What you may find is that the deep shadow texture may reach it’s maximum pretty rapidly. Depending on where this is in the volume, you might get too much shadow.

-M

#3

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