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Rendering with Arnold in Houdini and Solaris using the HtoA plug-in.
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user_data_string picking up primvar data on .1001.exr but not .<UDIM>.exr

Message 1 of 4
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user_data_string picking up primvar data on .1001.exr but not .<UDIM>.exr

Hi guys,


We seem to be having this issue where we create a primvar called tex_Diffuse with a full path to a texture and using the <UDIM>  tag it just renders red. But changing it to 1001 works fine. It's like it doesn't know what to do with the <UDIM> tag. 


Anyone else having this problem?



Message 2 of 4

I wouldn't expect user data with "<udim>" to work. That will end up as a recursive string token look up in Arnold, like <attr:test> where test="C:\temp\example.<udim>", and that's not supported. You'll have to have the udim separate from the rest of the user data string eg filename="<attr:test>.<udim>" where test=C:\temp\example"

// Stephen Blair
// Arnold Renderer Support
Message 3 of 4

Maybe I didn't explain it enough.


In solaris using karma, I am able to attach the following primvar to my prim:

I then access this primvar in the shader to drive the file path for an image node.

When I do the same in arnold, it doesn't seem to expand the <UDIM> token.

I can confirm that using a primvar without the <UDIM> token correctly reads the texture path into my shader, but using <UDIM> in the path causes it to fail


Is there something I need to change to make this work with Arnold? 

Message 4 of 4

Do you have an example scene? I don't know how it is exactly set up in your scene, or what happens when it is translated to Arnold.


But prim var = user data in Arnold, and user data with an embedded token won't work. There's no way I could set up Arnold (eg an ass file) to work with that.

// Stephen Blair
// Arnold Renderer Support

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