Prevent a material to cause shadows.

[Robert]

When I place things like labels on a mesh, I often use an extra polygon above, with a clip texture and the shader to cast no shadow. But V-Ray doesn't do that. Instead when turning cast shadow off, the effect is that clipping (V-Ray opacity map or Modo stencil map) is turned off. Still the object cast a shadow from GI light. It seem to work only for direct light. Also turning off the 'blackface' option on the shader, doesn't do that for GI. I guess for V-Ray GI a Material is always 2 sided?
Is there any option that does the job?

[vladimir.nedev]

Some core changes were made to how these "visibility" flags are handled in V-Ray Next.
This was required for the correct operation of the adaptive lights.

Visible to indirect rays is completely ignored and instead cast shadows is used for both shadow and GI rays.

Instead when turning cast shadow off, the effect is that clipping (V-Ray opacity map or Modo stencil map) is turned off.

In my tests this seems to be happening for the secondary rays only, is that correct ? Like in the first attached screen-shot.

Still the object cast a shadow from GI light.

I did some tests and this seems to be working.

Maybe what you are seeing is the shadow in the glossy reflections ?
You have to disable both visible to reflection rays AND visible to refraction rays, as otherwise V-Ray switches to a sampling strategy that practically disables the opacity map for the glossy rays.
I am not sure if this can be fixed.

Also note that making changes to these visibility flags requires an RT restart.

Greetings,
Vladimir Nedev

[Robert]

Thanks, for the hints. I could solve the problem with your advices.