[CDRDA]

I've been noticing several instances where specific materials are rendering with an incomplete alpha channel, where it should be completely white. The CPU render on the same material/scene renders fine. As a consequence, in some cases half of my render area is rendered semi-transparent! I have been rendering to SL12.

I seem to have narrowed this down to Bump/Normal maps. When disabled the alpha renders as expected. Enabled, the bump/normal map appears in the alpha channel (as varying shades of grey).

This occurs both with a v4 mxm, as well as a v5 mxm created from scratch.

When using a material with a very fine normal texture, the alpha renders seemingly how it should, but does not clear until at least SL11/12. Other textures I have tested are not clearing even at SL16.

Has anyone else experienced this?

[luis.hijarrubia]

Thank you for your test. We have a known issue about some render channels showing artifacts on GPU. Those artifacts are like black borders on some objects. Your issue is similar, just the border, or the whole object?

[CDRDA]

It is the whole object and it follows the bump/normal map. Removing this gets a clean alpha.

I tested a simple base material, just a single bsdf and rendered just with ref0, roughness and normal individually. Only the normal map affects the alpha.

As I mentioned, smaller less pronounced normals/bump maps seem to be resolved when rendering to higher SLs.


This alpha is just a plane without any subdivision.


This alpha was a more complex scene using a number of existing materials. As you can see there are various transparencies across the image, depending on the material. I can repair this somewhat by placing a 50% grey layer under the render in photoshop to replace the transparent areas. This is fine for draft images, but not good for when I come to do a final render.

[luis.hijarrubia]

Yes, this is a different issue. We will check all channels on gpu, and maybe adding one or two of the not supported ones. Thank you for your images.