Dear Community,

I have a geometry that I'm trying to do shell texturing with. I've used wrangles and the copy SOP to create several scaled copies of my original geo which get progressively more transparent -- each copy outward has a higher @Alpha than the last. By the end of the SOP the @Alpha property has been promoted to the vertices. In the Stage view, when rendering just the geometry, I can see the shell alphas showing the effect I desire.

However, when I add my material and turn on Karma, the whole geo disappears. I guess I'm applying the Alpha wrong. In my MaterialX material builder, I am reading the Alpha vertex property with the MtlX geometry property value node, and passing it to Opacity on the standard surface.

I thought maybe the outermost shell, which could be fully transparent, is also making the renderer cull interior shells. But even the most transparent shell only has an alpha of 0.1, so I would expect to see at least that. I guess it's something else.

Any solution to this issue is welcome!

For those interested, I got an answer on Discord:

USD has different names for common attributes
Cd is called displayColor, for example
i believe Alpha is displayOpacity
without the '@'

So using `displayOpacity` as the value in `Geomprop` allowed the material to use the correct opacity value, whereas Alpha, which didn't exist in the context, must have defaulted to 0.