Shell+DECAL = fail

[piotrek.m]

vray 6.0.0.6 hotfix, max 2023
Shell material with whatever plugged into (vraymtl, standard..) gives alpha/lighting error in Vray Decal pixels. In lightcache prepass everything is OK.

[hermit.crab]

No issues here. Could you attach the scene here (including the bitmap) so we can take a look?

[piotrek.m]

Here's scene, bitmap doesn't matter. Sorry I wasn't specific, shell material is on floor surface, decal is normal vraymtl
Decal with shell mat acts like 'cutter', projecting its inverted alpha on surface.
(decal with shell mat. also gives bug, it just doesn't work if you apply shell to decal object)

[piotrek.m]

With opactiy set to Clip it renders fine. Stochastic/normal gives error. But it's interesting bug, I can see practical uses for that...

[hermit.crab]

Thanks for the provided scene. It seems the issue lies in how Gradients are handled together with Shell Materials. I've logged it (internal bug-tracker id: VMAX-12467) for dev investigation.

With opactiy set to Clip it renders fine. Stochastic/normal gives error. But it's interesting bug, I can see practical uses for that...

Yes, that's because there is no gradient with the Clip mode (either opaque or transparent). Otherwise, you can work around the issue by abstaining from using the Shell shader. If you need a shader switch, VRaySwitchMtl is available (unfortunately, it has no viewport preview at this point).