incorrect lighting (or shading)

[bardo]

Hi,
I've a simple test scene that has a room with one window, 4 spheres and one parallelepiped near a wall.
The strange behaviour is that, if I put that parallelepiped near one wall of the room, the face that point to the wall seems emitting light.
If I put it far from the wall, everything come back to the lighting expected.
Just to show you
Far
https://i.imgur.com/PiFFkgr.jpeg

Near
https://i.imgur.com/rsLtS6z.jpeg

Another strange thing is that, the images shown before are obtained using a Solidify modifier on the wall geometry, giving it some thickness.
If I disable that modifier, I get back the emitting lighting.

Solidify ON (on the walls)
https://i.imgur.com/AaHX3oW.jpeg

Solidify OFF (on the walls)
https://i.imgur.com/uxb3eZU.jpeg

If you want to play with the scene, I've attached it.

[shaio]

Hey bardo,

That's an odd one. Based on a quick check at the scene, it seems like it's somehow related to the secondary rays bias, or at least it behaves like this. It also happens without the solidify modifier. We'll check it out. Thanks for the report.

ps: It looks like this is an issue with the V-Ray core, since it's present in the other integrations as well. It's quite visible here in Blender because of the scene scale

[shaio]

Ok, there is no issue here. It still related to the secondary ray bias but only for the shadows. The behavior is caused by the Shadow bias option for the Sun Light. The default value is too high for the scene scale and causes this behavior you're experiencing. Change it to something low and you should be good to go. We will change the default values for all lights.