But this doesn’t provide a seemless render, instead I get the “middle” of the scene rendered twice. How do I set it up so that the end result will look just like if I had done like this:
What you want to do is look at the definition of what gluPersepctive does. (It is in either the red or blue book) It creates parameters that it passes to glFrustum. You need to create the same parameters for the whole view, and then so that the left parameter is kept for the left screen half, but the right parameter is replaced by (left+right)/2. The right side is generated with similar parameter modifications.
Thank you very much! That glScissor solution worked perfectly! I had started implementing a cumbersome thing using the stencil buffer and clip planes, but this was just so much more elegant. Thanks again!