V-Ray GPU & RTX render shadows ignoring Opacity Map

[jymontoya]

Hello,

I'm having a continued problem trying to use VRAY RTX or CUDA GPU mode (RTX 4090) to render a material with a opacity map. This is a simple vinyl logo applied to a wall or display panel. This renders as expected in CPU mode, where there are no shadows visible from the opacity map as it is sitting just off the surface:



Whereas a RTX render shows a faint shadow as if the opacity map is not being correctly read by the RTX engine:



At first I thought this might just be missing the opactiy entirely but offsetting the logo to one side shows the opacity is intact, it's just this logo rectangle plane is dropping a shadow on the surface behind it, which it shouldn't be. Shadow casting turned off, etc.



I believe this has only started happening in VRay 6 for me and was working as expected in VRay 5. However, I cannot go back and check to confirm. Any idea what's going on here?

Thank you for your help.

[hermit.crab]

Mind if you send the scene so we can troubleshoot?

[jymontoya]

Submitted ID 234450

Thank you.

[hermit.crab]

Could you send the .max/.ma file instead? It would take ages to debug it from the .vrscene alone.

[jymontoya]

Sorry, but I don't use the horrible interfaced and bloatedly inefficent 3DSMax software.

I use FormZ and SketchUp which are much more designer friendly. This particular example was done in FormZ, which I assume isn't going to be something you could debug with? I can recreate it in SketchUp probably if that is better?

[hermit.crab]

A SketchUp file would be fine.

[jymontoya]

Hello again,

Thank you for your support. I was able to find a solution by digging deeper into the problem. Turns out the darker 'shadow' in RTX mode was being created by the Refraction IOR default setting of 1.6. I changed this to an IOR of 1, and the 'shadow' disappeared so now the RTX engine renders the same as the GPU for this Opacity map logo texture:



I do still wonder why this is just recently happening?

Thank you.

[Muhammed_Hamed]

Hi jymontoya

It doesn't make sense the refraction IOR creates a shadow, only visible in RTX mode. If we reproduce this on our side, we will be able to tell what is going on
Is there a chance you can share the setup with us? sketchup file should be fine
Thanks!

Best,
Muhammed

[cohab_projectsro]

Thanks jymontoya

This worked for me aswell.

[jymontoya]

Hi jymontoya

It doesn't make sense the refraction IOR creates a shadow, only visible in RTX mode. If we reproduce this on our side, we will be able to tell what is going on
Is there a chance you can share the setup with us? sketchup file should be fine
Thanks!

Best,
Muhammed

Hello, glad the 1.0 Refraction IOR helped someone else.

Muhammed-

Here is my SKP file you can see what is happening. We never used to have to set the Refraction IOR to have opacity maps render the same between CPU & GPU modes.

[natalia.gruzdova]

Hello jymontoya,

Thank you for your scene, I will need some time to perform tests and will let you know of the results. I do reproduce the issue you describe in a new scene and the unexpected workaround you have shared indeed works.

Another option that I would like you to consider instead of transparent material is to use Decal to project your logo over the surface. It is easy to use and control and the results are consistent.

[jymontoya]

Hello jymontoya,

Thank you for your scene, I will need some time to perform tests and will let you know of the results. I do reproduce the issue you describe in a new scene and the unexpected workaround you have shared indeed works.

Another option that I would like you to consider instead of transparent material is to use Decal to project your logo over the surface. It is easy to use and control and the results are consistent.

Thank you for your help.

I'm aware of Decals, and while they can work in some applications, they do not work for ours where we often have to share regular Shaded Style rendered views in addition to V-Ray renderings. Since V-Ray decals do not show in the regular Shaded style, they are not usable in our case.

[natalia.gruzdova]

I see, thank you for the additional details jymontoya. We have logged the issue internally (ticket VGPU-6602) and developers will look further into it. We will notify you on the forum if there are any changes.

In the meantime please use the workaround that you have encountered. Also note that the issue can only be reproducible if the background surface material is reflective.