I have a scene with a box that is open on the front with glass panels on the sides. Objects inside the box have an aluminum vray material applied to them. When rendering with gpu the alpha is incorrect.The objects inside of the box have some transparent spots when they should have none. When you turn off the reflections the alpha is correct. When rendered on cpu the alpha is correct. I’ve attached the scene file as well as images.
Has anyone run into this before?
Thanks in advance!
Thanks for the report. We are aware of the issue, it is already logged (internal bug-tracker id: VGPU-3825) and is awaiting developer investigation. It is linked to the ‘matte for refl/refr’ option in V-Ray GPU, so you may disable the option (located in the V-Ray properties of your matte plane) as a workaround.
Possibly because of the mentioned option, since with it off, matte objects won’t be matte through refractions. Could you post a screen? You might need to render twice for a correct alpha.
Sorry. i was not clear. the problem is when put glass in the front window the objects behind them become semi transparent in the alpha channel. I’ve attached another scene file.
Thanks for the help. reflection issue-glass.zip (5.03 MB)
What is even weirder is that if you look at the right side of the box, the torus knot to the right is showing (as in the reflection) in the glass’s alpha.
Thanks for the provided scene. Unfortunately, this is another known issue (internal bug-tracker id: VGPU-4147), with which our developers are already occupied. Sorry to say, there isn’t a workaround, except rendering your alpha on the CPU.
@hermit.crab Could be nice if the GPU alpha bugs could get a high priority.
In the next time V-Ray for Rhino could get an update and it could be great to get the fixes there since VfR updates are released quite seldom and I hope to see the fix not in a half year only.
Rendering the alpha per CPU is quite time consuming since CPU rendering is slow here.
