From:	Brinkerhoff <brinks AT ainop DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	More wonderful Allegro Clipping
Date:	Sun, 08 Mar 1998 00:23:03 -0800
Organization:	Dave's Machine Service
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Message-ID:	<35025567.1E08@ainop.com>
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Here's what I don't get about the u and v coords for texture mapping.

You say I should interpolate them the same way as the x,y coords.

Well suppose you have a quad poly.  It is a rectangle (4 90 degree 
angles) and two of the sides are perpendicular to the y-axis (this is 
basically what I'll be dealing with, anyway).  

Take a look at these wonderful ascii diagrams (viewed as though looking 
down)


            |                             /
(a)    ------------         (b)    ------------
            |                           /


(Let's just assume that the diagrams are basically the same, save for 
the fact that b's poly is rotated slightly, meaning that the distance 
from the end of a poly, to the intersection with the viewplane is the 
same in both diagrams) Now, buy calculating the u and v coords the way i 
did the x,y coords, it seems as though i would get two different vales 
for u,v coords, when in fact, they should be the same.

Can you explain more on how to interpolate the u,v texture mapping 
coords?

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