Strange shadow of object - what could be the reason?

[BeneZ]

Hello,

I am fighting with an object, that has a weird shadow.
I checked it, it's just a simple mesh. No inverted normals.

What could be the reason?

A simple round plane disc casts a correct shadow (in comparison on the left)

(IPR render)


Thanks

[3d-laboratory]

Also the shadow of the round plane is weird. I think it should fade nearly the same amount around the shadow edge, on the upper and lower side a bit sharper because of the perspective. How many lights? What happens if you lift the right mesh, so that you can see the full shadow shape underneath it? What material is the ground plane?

[BeneZ]

It's with every ground, the plane is already a test.

there are two lights in the scene, the double shadow is not the problem.

When I lift it, then th shadow is right. Only if it's CLOSE to the ground I get the wrong shadow...
Must be a strange clipping of vray. (opacity clipping maybe?)
Are there other render modes I can check?

[BeneZ]

With a shell operator it is not problem, only when it's thin as a leaf

[^Lele^]

Reduce shadow bias for the offending light, see if that helps.