nil if unsuccessful, otherwise :

M3_SHELL	Shell type
M3_CAM	Camera type
M3_LIGHT	Light type
M3_COLOR_LIGHT	Colored light type
M3_TOPO	Typology type
M3_MESH	Mesh type
M3_COLL	Collision type
M3_SPRITE	Sprite type
M3_PARTICLE	Particle emitting type
M3_LISTENER	Sound listening type
M3_SOUND	3D sound type
M3_ANIM	Animation type