how are you draw semicircle bei defining starpoint and endpoint or just a simple one
Vivi,
this is one of those questions that seems easy to answer… at first. Questions: Is this in 2D or 3D? Does the winding order matter (cw or ccw)? Do the end points define the complete semi-circle?
In any case, there are quite a few steps involved in solving this one.
You might want to take a look at the GLU specification. You can find it at
http://www.opengl.org/documentation/specs/glu/glu1_3.pdf
It provides a simple implementation for drawing semi circles using gluPartialDisk.