how or where can I input Cs in Vex builder when I am working on a Rman shading network?

thank you for your attention!

I don't write rman shaders but I think Cf is mantra equivalent of Cs.
I sure someone will put me right if that is incorrect though

Cs is defined on the object node's Shader folder. Os is also defined there.

but sometimes we may have many sops in one object node! We may want to assign different Cs value for different sops in that object node.
Can each sop(geometry) have its own Cs within one object sop?

I am glad you asked this.

Please append an Attribute SOP to your SOP chain. Go to the RenderMan folder. Check the "Add Default Mappings.

Now MMB to get the info on the Attrribute SOP. You will clearly see at the bottom all the attribute mappings. In there you should see Cd -> Cs and Alpha -> Os.

There you go. You can now use the primitive SOP, point SOP or vertex SOP and use the Color and Alpha parameters to control Cs and Os before the Attribute SOP configured as above.

Thank you
I will try it very soon!

jeff

I still cannot get it working.

e.g. if I am going to add a Cs for a sphere.
1) I attached an “attribute” sop after the sphere.
2) I went to the “renderman” page of the attribute, check the “add default Mapping” box

Should I put a “primitive” sop between the attribute sop and the sphere sop? Should I go to “Attributes” page of the primitive sop? Should I choose “add colour”?

in the attribute sop, what should I put for Houdini RiName and RiType?
I think I should put Cs for RiType. Should I choose constant colour for it?


Pls forgive me that I am a beginner!

brucelay
Should I put a “primitive” sop between the attribute sop and the sphere sop? Should I go to “Attributes” page of the primitive sop? Should I choose “add colour”?

Yes. You are correct. The Attribute SOP's default renderman mappings will take Cd and Alpha and map each to Cs and Os respectively. If Cd and Alpha do not exist, then you get zeros for Cs and Os. You can also use either the Point SOP or the Vertex SOP to add Cd and Alpha. All three SOPs work but they have to be before the Attribute SOP.

brucelay
In the attribute sop, what should I put for Houdini RiName and RiType?
I think I should put Cs for RiType. Should I choose constant colour for it?

No you don't have to do this for the “default” mapped attributes. You can find out what these default attributes are by Right Mosuse Button pressing on the Attribute SOP's icon after you check on default mappings.
You would only need to type in additional attribute names if you had custom attributes defined on your data and your RenderMan shader was set up to read that attribute.

Thank you Jeff!
It works!

many thanks!