SOLID_NONE		= 0 	-- no solid model
SOLID_BSP		= 1 	-- a BSP tree
SOLID_BBOX		= 2 	-- an AABB
SOLID_OBB		= 3 	-- an OBB (not implemented yet)
SOLID_OBB_YAW		= 4 	-- an OBB, constrained so that it can only yaw
SOLID_CUSTOM		= 5 	-- Always call into the entity for tests
SOLID_VPHYSICS		= 6