Fixed angle range for diffuse bounce
Fixed angle range for diffuse bounce

-- For diffuse bounce want to pick angles in the half-sphere above a surface (easiest to picture about a flat surface). So phi should range from 0 to 2pi however we want theta to range from 0 to (pi/2 - tolerance) where the tolerance is used to ensure that our particle does not have a direction pointing exactly parallel to the surface it is bouncing off.

git-svn-id: 9e43e5c0b822a6a38dd81306e184699a3a573cb4@22 7850984a-0f19-49c7-84f0-416d0ede6f3e

mjrasobarnett/ucnsim,mjrasobarnett/ucnsim,mjrasobarnett/ucnsim