Most OpenGL implementations, including SGI''s for Windows, have
extremely efficient clip-check code. The cost varies between
negligible and zero. Some hardware can rasterize primitives that go
outside the viewport for free, so it''s not worthwhile to do clipping
on the host. For this reason, you might as well leave clipping to
OpenGL. In pseudocode, you change this:
if (primitive isn''t rejected)
if (primitive is trivially accepted)
draw it
else
clip it
to this:
if (primitive isn''t rejected)
draw it.
OpenGL will clip it, or not, as the hardware requires.