Renderman cloth shaders

[a***@gmail.com]

Hello.

I need to write set surface shaders for a different sort of materials
such as silk, wool, cotton etc (without displacement shaders).
I've found not a lot of information in this task, where are only
publications on the simulation of clothes, but not cloth shading. I
have learned that for some materials I can use Oren-Nayar's shading
method; also it is possible to use Valvet - smth like this:
shiny += pow ( max ( Ln.V, 0 ), roughness ) * backscatter * Cl *
sheen;
shiny += pow ( sqrt(1.0-max ( Nf.V, 0 )*max ( Nf.V, 0 )),
edginess ) * Ln.Nf * Cl * sheen;
C = (Ka * ambient() + Kd * (diffuse(Nf))) + shiny;
Also I've found tutorial on creation of satin material in brazil - but
yet it was not possible it is achieved same in quality in renderman
Where can I find the information on which properties materials have
and which models of illumination I should use?
Any help or pointers would be hugely appreciated.
PS: Here is draft images I've made:
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Alexander

[Felipe Esquivel]

Post by a***@gmail.com
I need to write set surface shaders for a different sort of materials
such as silk, wool, cotton etc (without displacement shaders).
I've found not a lot of information in this task.
Where can I find the information on which properties materials have
and which models of illumination I should use?
Any help or pointers would be hugely appreciated.
PS: Here is draft images I've made
Alexander

In my opinion you have some options to solve this problem:

1 Mathematic: Study papers about measured BRDF (Bidirectional
Reflectance Distribution Function), there are plenty.
2 Artistical: Observing carefully how different fabrics look and add
these elements to your shader.

Felipe Esquivel

[a***@gmail.com]

Post by Felipe Esquivel

Post by a***@gmail.com
I need to write set surface shaders for a different sort of materials
such as silk, wool, cotton etc (without displacement shaders).
I've found not a lot of information in this task.
Where can I find the information on which properties materials have
and which models of illumination I should use?
Any help or pointers would be hugely appreciated.
PS: Here is draft images I've made
Alexander

1 Mathematic: Study papers about measured BRDF (Bidirectional
Reflectance Distribution Function), there are plenty.
2 Artistical: Observing carefully how different fabrics look and add
these elements to your shader.
Felipe Esquivel

Thanks for your reply.
I have found some interesting articles about Measured BRDF and now
i'll try to use these equations in shaders.
But it will be very cool if someone tell me some basic properties of
cloth materials, for example silk has a lot of anisotropic specular,
cotton is simple diffuse with low level of specular component, etc.