hi, first post in a loooong time :) please go easy :)

i've started off with a cube like arena with some random dots along the walls.

i then went and found the normal of each dot.

i'd like to filter out the normals somehow and i started this by using the law of cosines and the dot product. -- http://en.wikipedia.org/wiki/Dot_product

the problem is that although most of the normals on the floor are remaining, there are still many normals on the walls and i cannot for the life of me understand why? i specifically stated to only include those between 80 and 100 degrees (or equivalent in radians).

i use the x-y plane (1, 0, 0) and the normal (nx, ny, nz) in the equation.

i'm doing this all in c++.

any help here would be much appreciated, thanks!