I don’t know the answer, but I work with trees a lot too and I’m interested in everything about them. First of all, did you import these trees or make them in Tree Creator? If you made them in Tree Creator, you might want to check out this tutorial by Larsbertram and/or ask him on the associated forum. He might know.
thank you all for your replies. I’ve created the trees with maya and I think, it’s a texture-problem.
I’ve tried several things, but with no success. Does somebody know, how to fix this problem?