mtoa adding a custom LPE label/tag

[gothic3pl]

Hey,

I have been researching but I could not find the answer - how can I add a custom LPE label to object or material in Maya?

The documentation says:

For built-in shaders standard hair is labeled with 'hair', and the standard surface coat is labeled with 'coat'. All other built-in shaders components have no labels. So the following expressions could be used for example:

light_path_expressions 2 1 STRING

"emission_fire C<O.'fire'>"

I assume, in this example, emission of 'fire' material is taken into account, but what does 'light_path_expression 2 1 STRING" does and where do I put it? Is STRING the custom label for this material? what is 2 1? Also - can I label object instead of calling for material parameters?

Cheers,

Lucas

[Stephen.Blair]

You cannot add custom labels to existing shaders (not without access to the source code).

You can add custom labels in your own custom shaders. For example, in OSL:

https://answers.arnoldrenderer.com/questions/6589/can-i-isolate-geometry-using-lpes-in-arnold.html

*light_path_expression 2 1 STRING* is what you would see in an ASS file, if you exported a scene after setting up 2 LPEs in the Maya user interface.

[gothic3pl]

Oh, hah, thought it'd be easier than writing OSL shaders. Any ETA on object based grouping for LPEs?

Thanks

[ethan.crossno]

I would really like to see this possible as well. Would be really useful for emissive effects