Hello,

In this animation where the camera goes through the ocean (using a houdini procedural ocean in karma XPU), there is a brief moment where a dark line is visible as the camera is going through the ocean... I join here a close up video of the artifact... I thought it would be fixed by adjusting sampling limits of either refraction or volumes, but even with those at a high value, nothing changes... Any clue what could cause this, and how I could fix it ?

Thank you !

Try setting the KARMA_XPU_MAX_UNIFORM_VOLUME_SPANS envvar to a higher value. It defaults to 32, try 128 (or something)
Going too high will hurt performance, so be a little careful with it

brians
Try setting the KARMA_XPU_MAX_UNIFORM_VOLUME_SPANS envvar to a higher value. It defaults to 32, try 128 (or something)
Going too high will hurt performance, so be a little careful with it

Hello Brians,

That does fix it, thank you for the help! Do you have any pointers as to why this happens, so I can understand it better? Is it because of the very tangential viewpoint relative to the uniform volume edge? Is it linked to the refractive surface as well, or just the volume?

Anyway, I'm happy it's fixed, thanks again.

Its our "uniform volumes spans ray" can only capture a fixed number of hits/spans
https://www.youtube.com/watch?v=yY1m8NeryaI&t=767 [www.youtube.com]

This number is fixed due to the GPU's stack memory limitations. If we increase the number, the GPU will run slower. So, it's a balancing act about having enough, but not too much.