01/30/2003
15-462 Graphics I
12
Drawing on a Surface
•Shimmering when drawing shadow on
surface
•Due to limited precision depth
buffer
•Either displace surface or shadow
slightly
(glPolygonOffset in OpenGL)
•Or use special properties of scene
•Or use general technique
1.Set depth buffer to read-only, draw
surface
2.Set depth buffer to read-write, draw
shadow
3.Set color buffer to read-only, draw
surface again
4.Set color buffer to read-write