Subject: random black pixels near edge of image

(This message is being sent to CPSC 215 Students and TA's)

A student writes:

 > I've found that when I have planes (walls) intersecting the edges of the screen,
 > some pixels along that edge are black (or show through to something behind that
 > plane if applicable). Is this normal? As far as I can tell, it's a math precision
 > issue where the Z coordinate of the hitpoint is very near zero.

That is indeed related to math precision.  I won't deduct for it but
if you want to get rid of it that can generally be accommplished
in plane_hits by changing:

    if (hitloc[2] >= 0)
       return (-1.0);
    to

    if (hitloc[2] >= 0.0001)
       return (-1.0);