VRay fur renders black and I don't know why

[newnoob]

I'm using Vray fur for grass on several components. Inexplicably the fur hair renders completely black on certain components and on other components it renders how it should be and I don't understand why.

I have spent a considerable amount of time trying to resolve the issue. I've reinstalled Vray. I've deleted all interior lights which were placed inside the component because I was thinking that the light from the inside of the component might interfere with the fur on the outside. I have erased all materials from the misbehaving component so that there is nothing left other than the component with SU default material but fur is still rendering black.

Solutions and suggestions why this issue occurs are highly appreciated!
Thanks!

I've already opened the same thread in the sketchucation forum and uploaded pictures and my SU modell.

[newnoob]

I've found out that the fur issue starts appearing on geometry after I use the SU solid tools on this geometry .

before solid tools union:https://drive.google.com/open?id=0B_...Gtlckx0RlJDeVU
after solid tools union: https://drive.google.com/open?id=0B_...0lMSnB0cDViQ3M

[newnoob]

I could resolve the issue by using ThomThom's plugin Material Tools.

It seems that when a solid tool operation is executed with geometry with materials applied to the geometry the material from geometry A might transfer to geometry B and can sit then at back faces or faces invisible from the outside or inside of a component and that can cause the issue.


After I applied Material Tools>Remove from Selection to the misbehaving geometry the issue with the black fur disappeared and the fur rendered normally.