Subject:    -7- Is there a performance cost using a software layer on
                top of GL?
Date: 30 Apr 1994 15:45:00 CDT

  Sometimes. Note that few GL programs achieve peak graphics
  performance. This is because most applications have natural
  application overhead, and also because many programmers lack a
  thorough understanding of the details and eccentricities of GL. If
  you are writing a simple display-only, immediate-mode GL program,
  then it will run faster using straight GL, but not much. However, if
  your program has scene traversal, interactivity, picking, bounding
  box calculations, and other object space tasks, then Inventor will
  perform better for you. This is because Inventor is specially tuned
  to make optimal use of GL on each SGI machine. Furthermore, Inventor
  supports render caching which results in peak GL performance in most
  cases.

  We have found that in many cases, Inventor programs run FASTER than
  the original GL program, and that the programmer productivity
  increases easily outweigh the overhead of the toolkit.