When you say 'divide with it' how do you mean? Sorry - my maths is extremely poor :)
Assuming Nx, ny & nz are the normals .. to normalise them so that vector magnitude = 1 do this ...
l# = sqr( nx * nx + ny*ny + nz*nz )
nx = nx / l
ny = ny/ l
nz = nz/ l
Say I have a ball moving at angle A towards a block, how would I calculate the new angle B when it bounces? I know its something to do with surface normal of the colliding object...
Take a look at this ..
http://www.blitzbasic.com/codearcs/codearcs.php?code=670
Stevie