"Bald Eagle" <cre### [at] netscapenet> wrote:

> a is the squared length of the direction vector
> which, if non-zero, the vector cross product length gets divided by,
> which should be the shortest, perpendicular length.

a is the squared length of the PROJECTED direction vector

> A few minor problems.
> The ray direction vector already gets normalized at the beginning of
> Sor_Intersect, so why are we calculating it's length again, and then checking if
> it's more than zero, when at this point it should always be ONE.

Because although the RAY is normalized, it's PROJECTION isn't unit-length unless
it's parallel to the xz plane.

> Which bring up the potential divide-by-zero error when the normalization
> calculation is done - and there is NO checking THERE!
> And then there is the vector cross product sign issue.
>
> So, after this gets rigorously checked, I'd suggest that
> 1. the ray direction vector length check gets moved to earlier in the code

> 3. Line 276 r0 = P[X] * D[Z] - P[Z] * D[X];
> should be r0 = fabs(P[X] * D[Z] - P[Z] * D[X]);
> so that the "length" is always positive.

- BE

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