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Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
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Defining Hair Properties Using Vertex Map

Message 1 of 6
793 Views, 5 Replies

Defining Hair Properties Using Vertex Map

I'm in the process of creating a character which uses UDIM textures. Our almighty Arnold renders the UDIMs no problem, but Cinema 4D still lacks official UDIM support. I'm in the process of adding hair/fur and running into a limitation.

I'd like to use a texture to define the length and density of the hair. Typically, I'd do this using a UVed texture map, but this doesn't work due to UDIMs. I decided to use a vertex tag instead, which works beautifully since you can use Field's to define areas of density/length. Vertex tags being used to define hair parameters renders perfectly in Physical, but Arnold doesn't seem to read the vertex information. Arnold does work properly if the parameter is driven by a gradient or noise, for example.

Is there any way to make Arnold respect vertex-map-drven hair parameters, or is this a limitation of the engine?

My alternative solution will be creating a second UV space without UDIMs and creating texture maps for those properties.

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Message 2 of 6

What if you add an Arnold tag to the Hair object and enable Render via Hair Render effect on the Advanced tab? If that does not work, could you please send me a basic scene?

Message 3 of 6

Sure! I tried turning on "Render via Hair Render effect" as well as "Export IDs" and "Export UVs", neither of which made any difference.

I created a quick test scene for you. It uses a Vertex Map with a Linear Field to drive both the density and the length in the C4D hair material. First image is the result from Physical, and the second is Arnold, which doesn't respect the Vertex Map.

Thanks for taking a look Peter, I appreciate it!



Message 4 of 6

Rendering your scene via the Hair Render Effect works fine here (C4D S22, win 10, C4DtoA 3.1.0).


Did not do anything, just opened your scene and pressed Render.

Message 5 of 6

Strange. I updated to the latest version of Arnold (3.1.01), although I'm still using R21 rather than S22. I'm not able to replicate the result you're getting. I also gave it a whirl in R20 running Arnold, vertex maps aren't reading there either.

Thank you for taking a look, it's good to know that it's possible for it to work. Might try installing S22 to give that a try. R22 must be right around the corner, huh?

Message 6 of 6

I was trying in R20 with C4DtoA 3.1.0 and it's working fine. Not sure what's wrong there.

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