AlphaChannel with GPU-Rendering

[pardalis]

Hello,

I don't get any alpha channels rendered in GPU rendering. Has this not yet been implemented or does something have to be taken into account in the render settings? The alpha channels work in CPU rendering.

RTX 3090, NVIDIA driver 461.09

best regards
uwe

[aleksandar.kasabov]

Hello pardalis ,

I did some tests but I did not have any issues with the alpha channel when rendering with V-Ray GPU. Can you please share a test scene where the issue is reproducible and your results with V-Ray CPU and V-Ray GPU so we can have a look?

[aleksandar.kasabov]

Hello pardalis ,

Thank you for sharing your test scene with me in PM. I checked the scene and I noticed that you are using "Object Select" render element. Keep in mind that "Object select" is only supported on V-Ray CPU and is not supported on V-Ray GPU. You can find a list of the supported features based on the render engine here.

[pardalis]

Hello Aleksandar,

thank you for your prompt reply. So far I have only ever issued the individual alpha masks with Object ID in Vray 3.7 or Object Select in Vray5. How does the workflow now work so that I get an alpha mask for each individual object? In all of the years with Vray, I haven't needed anything other than alpha masks. It's my first day with the Vray GPU and I still have to get used to the other workflow.

Best regards
uwe

[shaio]

Hi pardalis ,
to get the alpha mask as you used to do with V-Ray 3.7 in V-Ray 5 you need to use the MultiMatte render element in V-Ray 5. set all R, G and B id values the same as your the Id you've set object properties tag, and you will get the same result as in V-Ray 3. I'll be making a video about this to explain why there is such a difference so stay tuned about this. More Information about the MultiMatte render element could be found in our Documentation

[shaio]

Hello Aleksandar,

thank you for your prompt reply. So far I have only ever issued the individual alpha masks with Object ID in Vray 3.7 or Object Select in Vray5. How does the workflow now work so that I get an alpha mask for each individual object? In all of the years with Vray, I haven't needed anything other than alpha masks. It's my first day with the Vray GPU and I still have to get used to the other workflow.

Best regards
uwe

Hello pardalis .
I've made a video in this thread describing the difference between the ObjectID and MaterialID Render elements in V-Ray 3 vs V-Ray 5 and how to use them in V-Ray 5

[pardalis]

Hello Ivan,

thanks for the video. Progressive rendering over the VFB with MultiMatte is no problem. If I render MultiMatte with DR rendering and Vray GPU, I have problems and my masks look different. They are red and not white.

Best regards
uwe

[shaio]

Hey pardalis ,
this is a V-Ray GPU issue that is affecting all V-Ray integrations and unfortunately isn't only when using DR. It is reproducible when rendering on the local machine as well. I'll forward this to the developers and report it in our system. Thank you for the feedback.