A Trip Down The Graphics Pipeline
Whenever I start a new graphics engine, I always spend a fair amount of time
flipping back through older graphics books. It is always interesting to see
how your changed perspective with new experience impacts your appreciation of
a given article.
I was skimming through Jim Blinn’s “A Trip Down The Graphics Pipeline”
tonight, and I wound up laughing out loud twice.
From the book:
P73: I then empirically found that I had to scale by -1 in x instead of in z,
and also to scale the xa and xf values by -1. (Basically I just put in enough
minus signs after the fact to make it work.) Al Barr refers to this technique
as “making sure you have made an even number of sign errors.”
P131: The only lines that generate w=0 after clipping are those that pass
through the z axis, the valley of the trough. These lines are lines that
pass exactly through the eyepoint. After which you are dead and don’t care
about divide-by-zero errors.
If you laughed, you are a graphics geek.
My first recollection of a Jim Blinn article many years ago was my skimming
over it and thinking “My god, what ridiculously picky minutia.” Over the last
couple years, I found myself haranguing people over some fairly picky issues,
like the LSB errors with cpu vs rasterizer face culling and screen edge
clipping with guard band bit tests. After one of those pitches, I quite
distinctly thought to myself “My god, I’m turning into Jim Blinn!” 