Black bugs in Reflection

[eistan]

Hi everyone, maybe somebody know what is it, this is happens when u have reflection and bump together, any bump actually, clamp and fit didnt help at all, texture has a white point 0.9 and 0 black, and power of bump is 0.1, so everything is ok, seems, but here the screen and black bug i have

and here is the simple scene i made, there is only refl and bump and environment

scene

https://drive.google.com/open?id=0BxCxauJ6o6VVWGU1T0M1NW9GT1k

i dont know what is it and how to fix it

[Atom]

Are you using At Ray Limit Use Black Background? If so, try the other option and put something in the background for max limit rays to grab color from.

[MENOZ]

I think it is because the bump produces a normal in some parts which points backward to the object itself. So when mantra is trying to calculate the reflection is looking back into the object and returns black. Not sure where the black color is coming from though, if it's because it actually samples something black, samples the infinite, the inside of the object, some parts not shaded.. don't know.

just to make it clearer, if you were using displacement those parts would be facing away from camera and you won't see them.

You can put P and N from the compute displacement into the P and N of the displacement output node in your shader, and disconnect the normal from the surface model.