   Trimming NURBS sphere
  I am trying to make a sphere with a circle hole. I made 1/8 piece of sphere like this:gluBeginSurface(nurb); //I begin surface proc  gluNurbsSurface(nurb, 6, knots2, 6, knots2, 3 * 4, 4, &pts3[0][0][0], 3, 3, GL_MAP2_VERTEX_4); // draw my 1/8 sphere  gluBeginTrim(nurb);  //begin trimming    gluNurbsCurve(nurb,knotCount,*knots,stride,*control,order,type) Place, where I am stuck.   gluEndTrim(nurb);    //end trimminggluEndSurface(nurb);  //end surface procThe thing is, I dont know, how to trim half circle out of my 1/8 sphere.This is picture what I want to do, please look at it:http://img228.imageshack.us/img228/8350/trim.jpgI will wait any help. Thank You   