subroutines perpec and lookat

[ccsupos%prism at GATECH.EDU]

Hi, I am using the subroutines "perspective" and "lookat" on
IRIS 4D120GTX. I did not think I needed to push or pop matrices
in order just change the projection, viewpoint and the point that is
looked at. However, I cannot get the routines to work correctly
so I am wondering if I did not miss something. I would appreciate
any help on this as the user's guide is not very detailed.
Olivier Schreiber