Have anyeone read Bas Kuenen''s ooengine source code? I got some problem with its matrix part: I don''t understand why RotateX and RotateZ is different from the matrix representation of 3D transformation: 1 0 0 0 glRotate*(a,1,0,0)= 0 cos -sin 0 0 sin cos 0 0 0 0 1 cos 0 sin 0 glRotate*(a,0,1,0)= 0 1 0 0 -sin 0 cos 0 0 0 0 1 cos -sin 0 0 glRotate*(a,0,0,1)= sin cos 0 0 0 0 1 0 0 0 0 1