First I want to thank Sven for solving the problem with the missing normals. But now I am a little bit confused. I'm sure to heard about that if you specify the vertexes of a polygon (with glBegin GL_POLYGON in c) counterclockwise then the normalvector is set automatically. That means if you look at a plane the normal vector points to you. Is'nt that true? My example problem seems to show that this is definitly not true. So if I want to use light (and that will be very often) and I have to specify these vectors by myself then I can't use the renderPrimitive Polygon or Quad in situ because the calculation of a normal vector of a polygon isnt that trivial. The simplest way I see is to reduce this calculation to a normal vector calculation of a triangle. So I'm forced to define a new function makePoly taking a list of Points, calculating the normal and draw a polygon with this points. Otherwise I have to write down some points more then one time, the first time in the makenormal-function and in the secont at the render call. 1. Is this the way? 2. Where is it used that normals aren't right-angeled to the polygon-plan? 3. Exists there some higher-level function. With best regards Patrick