[vox-tech] OpenGL - perspective projections

[MAPSp@dirac.org (Peter Jay Salzman)]

Hi all,

In my little snatches of spare time, I've been reading a book on OpenGL.
Don't care much for the book, but that's the breaks.

I have a question about the projection matrix.

When I draw stuff to the screen, OpenGL takes care of perspective for me.
In other words, when I put a triangle centered at (0,0,-1), it apears bigger
than a triangle centered at (0,0,-999999).  I don't have to play with a
projection matrix for this to happen.

So, then, what exactly is the projection matrix used for?

Thanks!
Pete

-- 
The mathematics of physics has become ever more abstract, rather than more
complicated.  The mind of God appears to be abstract but not complicated.
He also appears to like group theory.  --  Tony Zee's "Fearful Symmetry"

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