Perspective simulation

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Tel 8663 ou 8357 (CHRISTOPHE.C.D.DELEPINE++at++TTS.thomson.fr)
Mon, 8 Jan 1996 17:58:37 +0100

This is more a GL question. Here it goes:

I would like to do the perspective computation in software (just as an
exercise). To do this, I multiply each vertex coordinate by the perspective
matrix then divide by -z. I send those new x,y,z values through the pipeline
making sure the projection matrix is loaded with identity. This works fine.
I get the same image than if I had sent original coordinates with a
perspective matrix loaded onto the stack.

The problem arises with texture coordinates.

If i assign the same u,v coordinates to the new x,y,z values, the inter-
polation along the polygon is incorrect.

Is there a trick so that the interpolation takes perspective into account ?

I can provide with a simple test case if needed.

thank you

Christophe DELEPINE
delepine++at++tts.thomson.fr

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