Decal inverting in Vray

Can anyone tell me why my decals are appearing inverted in VRay?
Looks as expected in the viewport but the alpha is being inverted in vray, no matter how I try and flick the settings…
Looks the same on CPU, Cuda or RTX…

This is the image I’m using. No alpha or colour mask selected. Trying all the different configurations of options doesn’t seem to help in vray. The Rhino Render window changes, but not in vray…

Hello, Andrew,

Can you please share the following info that can help shed more light on your issue?

  • Rhino version used (Help > About Rhinoceros)
  • V-Ray for Rhino version used (V-Ray > Help > About)
  • What decal mapping style is used - cylindrical, spherical, etc?

Kind regards,
Peter Chaushev
V-Ray for Rhino Product Specialist

Hi Peter,

Rhino Version 7 SR24
(7.24.22297.11001, 2022-10-24)

V-Ray for Rhinoceros 6 4.20.03
Build: 03 Hash: 7ed8aa22a Date: Aug 7 2020
V-Ray NeUI Version: 3.4.1 Build: 151708 Hash: f9c7596c4 Date: Jul 31 2020
V-Ray Core Version: 4.30.03
V-Ray AppSDK Version: 2.90.00

​Surface mapping using Closest Point projection​
Any clues? It’s happening to another object in the file…
Here’s a link] (Dropbox - sign.3dm - Simplify your life)

Andy, you shall not be running V-Ray for Rhino 6 on Rhino 7

Hello, Andrew,
Thank you for sharing your project with us and apologies for the late reply!
The way metallic materials work in Rhino (and V-Ray generally) is they get their appearance from their reflective parameters not from their diffuse color. The diffuse base is actually black for most materials.

When V-Ray renders an object with a Rhino decal, the decal texture is read as if applied to the material’s diffuse. This, however, is problematic when it comes to metallic materials.

While we investigate potential solutions on our side, I can offer a couple of workarounds:

  • Use a material other than metal e.g. a plasitc or a custom one.
    Furthermore, use an image file with a valid alpha channel. Here’s a png with no background (click on the thumbnail below to download it).
    Lastly, ensure the Decal texture’s alpha channel is utilized.

  • Use V-Ray Decal to set up the image over the metallic plate. Here is some info on the V-Ray Decal functionality:

Hope this helps!

Kind regards,