API reference

Three namespaces, and you almost certainly want the first.

Namespace	What it is
Box3D	The idiomatic surface. Start at PhysicsWorld, then Body and Shape.
Box3D.Native	A literal mirror of the Box3D C API: the same names, the same signatures, no abstraction.
Box3D.Interop	The one sanctioned bridge between the two, as extension methods.

Everything in Box3D validates its input, manages nothing you did not ask it to manage, and allocates nothing on the simulation path.

Nothing in Box3D.Native validates anything or manages a lifetime. Passing an invalid identifier crashes the process rather than raising an exception. Reach for it when you need one of the roughly 580 exported functions the idiomatic surface does not cover yet — the native layer explains the boundary, and API coverage lists what is on each side of it.

Importing Box3D.Interop is what makes reaching for the C layer visible in your own source.

Where to start

Looking for	Type
Creating and stepping a world	PhysicsWorld
A physical object	Body, BodyDefinition
Collision geometry	Shape, ShapeDefinition
Ray casts and overlaps	RaycastHit, IRaycastCallback
What happened last step	WorldEvents
Constraints	Joint and the nine specific handles
Terrain	HeightField, CollisionMesh
Character movement	CharacterMover
Drawing the simulation	IDebugDrawer