ray_plane_intersect [function]
ray_plane_intersect( vec3 ray_pos, vec3 ray_dir, vec4 plane )
tests for an intersection between ray and plane, returning all relevant output data
- if ray is (near-)parallel to plane, false is returned
- otherwise, signed distance along ray and signed origin distance from plane are returned
- if signed distance along ray to plane is larger than 0, plane is in front of ray
- if signed distance from origin to plane is larger than 0, ray origin is in front of the plane