Just to ley you know, I got the following response back from e-on on this issue. "I did not check the thread on renderosity, but got your file. Indeed, a few cherry trees appear on the black line where they should not. I guess this is a precision problem with the way the density function is evaluated. I tried increasing the tree density to 100%, and reduced the scaling to 0.2, and the trees were placed everywhere on the terrain, except on the black line. If you replace the trees with stones, it also works fine." I am not sure if this means that the problem will be fix or that we have to live with the work around. Stewart