Problem with EXR Deep when using opacity maps

[oliver.sullivan]

non deep alpha channel


deep alpha channel

The images show the alpha channel on the same frame, rendered deep and non-deep. As you can see, the deep version is quite different (RGB channels are fine, and render exactly the same both deep and non-deep). I'm guessing this is something to do with using VRayMtls with opacity maps for parts of the trees. Not sure if this is related to this old thread here?

Anything I'm doing wrong? I've tried in VRay 3.0 and VRay 3.1 with the same result.

Thx!

[vlado]

In the render elements section, there is an option "deep fragment merge mode" - set it to "by z-depth" and see if it helps.

Best regards,
Vlado

[oliver.sullivan]

Hi Vlado

It's currently set to "by z-depth" - switching back to "by render ID" does fix the problem, but introduces an issue we were trying to avoid, namely that it won't generate deep samples for the edges of any objects that self occlude. We can probably work around this for now.

Any ideas what's happening when we use the "by z-depth" option - looking at the deep samples for areas where the alpha differs, there are multiple samples but none with a value of 1, which I'd expect..?

[vlado]

Can you send me a scene for this to vlado@chaosgroup.com so that I can take a look at what's going on?

Best regards,
Vlado

[oliver.sullivan]

Thanks, I'll try to package something up early next week