Any chance you could submit a hip file that demonstrates the issue? You can email support@sidefx.com if you're okay sharing the hip file with SideFX but don't want to post it publicly.
On a given hip file/frame/geometry does this happen consistently (i.e. the same polygon is black every time you do a render)? Or does it happen randomly (the same render done multiple times, the black polygon only shows up sometimes)?
Any additional info would be appreciated because at first glance this looks very bug-like...
Ok I go on rendering phase this weekend so I'll have probably more info about this "bug ?" recurrence soon and tell you.
For more info I rendering a big ground map composed of 107 textures of 8192 square pixels. I'm using karma xpu.
I also notice on other frame a similar problem where small polygons and very few (2/4 primitives) don't turn black but dark like with a normal bug. Once rerendered they became a bit more corrupted (8/9 primitives), then I triangulated and problem is gone(I hope).
I have heavy assets (like textures) but I can share you soon for more investigation.