•Stacks for Modelview and Projection matrices
• glPushMatrix( )
–push-down all the matrices in the active stack one
level
–the top-most matrix
is copied (the top and the second-from-top matrices are initially the same).
• glPopMatrix( )
–pop-off and discard the top matrix in the active stack
•Stacks used during recursive traversal of the hierarchy.
•Typical depths of matrix stacks:
–Modelview stack = 32 (aggregating several transformations)
–Projection Stack = 2 (eg: 3D graphics and 2D help-menu)