Rendering grass with white dots/holes and darker texture

[Alpcgmd]

So, i'm using sketchup 2013 and vray 2.00 with the config i've always used, but now the grass seems to have some holes in it or white dots. I know about sub-pixel mapping by some other topics but nothing is working here...

Another problem is the same grass vismat that looks different from the left to the right part. The sun is at its zenith, so the shadows should be making an ""inverted bridge" if there was no empty space in the middle (deactivated the river for faster render)

[rspierenburg]

Try sub-dividing your grassy faces into smaller sections, this will help with displacement issues.