Todd Manus

Ok.. folk, I figured out the issue :-).. really really simple.
There is a mtlximage node inside the materialx network that creates the ocean surface shader... Karma reads the node with no issue because it is an *.exr file (oceanramp.exr)... Renderman can't use that oceanramp.exr file natively... it needs to convert it to a *.tex file with the colorspace of your choice... in my case (ACES).. so I had to edit the materialx ocean surface shader to fix that.

Hey Heileif,

Thank you for pushing me to make sure that I was 100% sure if the foam primvar is read by Renderman... it is being read. :-)
The issue was a two part problem:
1) I should have been on a frame further in the sequence, so it was given time to actually see the "foam"/points to show up on the surface. Even then, it wasn't correct.
2) I had to add the edit material network node for the mtlxoceansurface and change the foam color, foam transmission color, and transmission intensity to get the right look. Not sure why I had to do that. Do you think it is some weird translation issue with how Renderman read transmission info on the materialx network? The attachment isn't anything great.. but I have it working. Not sure why I have to change those colors in Renderman and not in Karma. Isn't materialx, just materialx?

Update: The fact that the renders don't look the same or close to the same between Karma and Renderman is bigger deal than I first thought. Lookdeving the foam color and wave color are a mess in materialx with Renderman. I'll keep trying to figure more of this out. I have attached the scene for anyone to look at. You will have to make the spectrum geo for the ocean and foam.. i didn't include to save on space.

Thanks again.

Hey Heileif,

You are correct in that I don't need the volume shader... I just assume that it is critical to getting foam working... The ocean tool is so integrated with Karma... When SideFx mentions that the tool works with 3rd party hydra-delegates, I was hoping that it would have been more plug-and-play. Naive, I know :-). It looks like Renderman can read the cusp attribute/primvar. I just had to boost the intensity to see the effects... I am still lost in how to use that data, and foam is still an issue. Again, if there is anyone at SideFx that would like to join the discussion? The end goal is to get parity between how Karma uses the tool vs how 3rd party hydra-delegates are expected to use the tool.
Heileif, I think the kma_volume shader node plays an important role in the foam stuff. So even though we don't need it in our renderers to get good results, I think it really is needed for foam. SideFx please help :-).

BTW... all screenshots, I am using the native materialx shader... I am not using any pixar shaders.