NaN error.

[pwp71]

ok, I've understood what is the problem in some NaN cases

Keep attention to:
- division by 0
- sqrt( -x )
are the root cause of many problem.

In this case some "Detected NaN in elevation" were due to this formula:

u = alpha / ((v * (alpha_11 - (1.0))) + (1.0));

Sometimes, v = 1 and alpha_11 = 0, so -> u = alpha / 0 -> NaN

"Detected NaN in origin vector" is still open but I'm working also on it.

Tell me a feedback about "Detected NaN in elevation". Thanks.

pwp71

P.S. done, rev. 1439