Thanx for that nice engine, Niko!
I have found a little problem with the camera settings. Zbuffers are not symmetrical in their resolution, so distant objects show artifacts very quickly. This is why a wbuffer should be used in some cases. In order to use the resolution of a zbuffer in an optimal way, the nearvalue of the camera should be as big as possible. For example, if the camera has a size of 30, the nearvalue can be about 30/sqr(2). Unfortunately, it seems that the skybox has a size of 1.0, so if the nearvalue is increased, the box disappears. I found that setting the l-value in the skybox function to about 1000.0 (instead of 1.0) solves the problem. I hope this will be fixed in the future!
Balu