Diffuse map alpha as transparency not working when rendering w/ GPU

[jay_louden]

Hello, everyone.

I have a simple test scene I'm running featuring many trees w/ a .png leaf material with transparency. In V-ray for Sketchup 3.60.03 ( Sketchup Pro 2018 ), I notice that rendering w/ CPU correctly uses the alpha channel as transparency, but changing to GPU rendering (with no other changes) the alpha transparency does not work, as seen below.

Is anyone aware of a reason why this simple toggle would cause that functionality to break? Is this a known problem, is it card-dependent, etc.? For what it's worth, this is on an RTX 3080.


Thanks!

[georgi.georgiev]

Hi jay_louden

Could you please post a screenshot of how the material is setup?

Also, could you share a sample scene to investigate the issue in detail? If this is alright, you could send an archived copy (Extensions > V-Ray > Pack Project) to support@chaosgroup.com via email or a file-sharing service of your choice.

[jay_louden]

Georgi,

Thanks for your response! I will send the packed sample scene to the support email as you suggest. Also, here is a dropbox link to a folder containing that .zip and the below files.

In the meantime, here are some additional images: The material setup, the CPU output vs. GPU output, and the light cache pass for the GPU rendering. I thought it might be relevant that the light cache pass appears to rendering the transparency correctly (including the shadows). I should mention as well that I am using V-ray Proxies here, as well, in both CPU and GPU examples.

Thanks again for any assistance you can provide.



CPU rendering output:


GPU rendering output:


GPU light cache progress:

[jay_louden]

Also, my apologies for the delayed response!

[konstantin_chaos]

Hi jay_louden,

The Diffuse Map Alpha as Transparency option in V-Ray 3 is not supported on the GPU.
A similar setup in V-Ray Next or V-Ray 5 should render as expected.
If you want to achieve a similar result in V-Ray 3.6 just use a Generic material with a single VRayBRDF layer.
The texture goes in the Diffuse slot of the material and then you can enable the Custom Source option in the Opacity section.
Make sure that Diffuse Texture Alpha is selected there.

Hope that helps,
Konstantin

[jay_louden]

Konstanin,

Thanks for the explanation, that settles it!