The software renderer uses Bresenham's line slice algorithm as presented
by Michael Abrash in his Graphics Programming Black Book Special Edition
with the serial numbers filed off (as such, more just so *I* can read
the code easily), along with the Chen-Sutherland line clipping
algorithm. The other renderers were more or less trivial in comparison.
Finally. I never liked it (felt bad adding it in the first place), and
it has caused confusion with function and global variable names, but it
did let me get the render plugins working.
