Transforms position from viewport space into screen space.
Viewport space is normalized and relative to the camera. The bottom-left of the camera is
(0,0); the top-right is (1,1). The z position is in world units from the camera.
Screenspace is defined in pixels. The bottom-left of the screen is (0,0); the right-top
is (pixelWidth,pixelHeight). The z position is in world units from the camera.
no example available in C#