This is your selection filter, it dictates what types of objects you wish to be capable of selecting in the editor. From left to right these are:

	PRIMITIVES
	Primitives are the basic physical collision entities that are created by any physics engine. They are usually basic boxes, spheres and capsules. A primitive is invisible in-game. It purely serves as a collision volume. A primitive needs to be part of an Actor to appear in the simulation.

 

MODELS

You should know what a model is, its a mesh, made in milkshape or 3ds max for example. These are what your engine renders and represent the only portion of a physics entity that should be visible in-game. On its own, a model is completely static and has no physical properties or collision detection. A model needs to be part of an Actor with at least one primitive, in order to appear in the simulation.

 

	ACTORS
	An actor is a combination of primitives, models and lights, to form a single physical entity. Effectively an actor should contain at least 1 model (to be rendered) and 1 primitive (for physics). Actors can be linked by Joints.

 

	CENTER OF MASS
	The center of mass of an Actor is automatically calculated, but if you wish you can have manual control over its position. This filter button allows you to select the green Center of Mass Gizmo that will appear if an Actor has a manually positioned Center Of Mass.

 

	BONES
	Bones are used in models with skeletal animation. The bones will automatically show if a loaded model has a skeleton. By attaching primitives and models to a bone, we can create characters and ragdolls.

 

	JOINTS
	A joint is a physical constraint, such as a door hinge or a wheel axis. Every joint must link at least one actor. If you link to only 1 actor instead of 2, then the actor will be constrained to the static world.

 

	JOINT LIMITS
	This filter simply makes the joint limits visually represented. The light blue planes represent the minimum and maximum angles or rotation the joint can rotate to. This feature is currently only active on hinges and ball joints.

 

	LIGHTS
	These will be less commonly used, but usefull nonetheless. Used for headlights on cars, or a rotating police siren for example.