unity-physicscore2d-bodies

Start from PhysicsBodyDefinition.defaultDefinition, set type to PhysicsBody.BodyType.Dynamic along with position, velocity, and gravity scale, then call world.CreateBody(def). Add at least one shape with nonzero density so the body has collision area and mass.

Static bodies never move and only collide with Dynamic bodies, suiting level geometry. Kinematic bodies move via code-set velocity and also only collide with Dynamic bodies, suiting moving platforms. Dynamic bodies respond to forces and collide with everything.

PhysicsCore2D uses a Write-Once-Read-Many model that forbids creating or destroying bodies during simulation callbacks like IPreSolveCallback. Defer structural mutations to IContactCallback, which runs after the simulation step on the main thread.

Read body.massConfiguration, override the mass, rotationalInertia, and center fields, then assign it back. This manual mode overrides the automatic density-based computation, useful for fixed character weight or lowering the center of mass to prevent tipping.

Sync in LateUpdate using PhysicsMath.ToPosition3D and PhysicsMath.ToRotationFast3D with the appropriate TransformPlane such as XY or XZ. PhysicsCore2D bodies are not attached to GameObjects, so manual per-frame synchronization is required.

The most common cause is forgetting to set the body type, since PhysicsBodyDefinition defaults to Static which never moves. Also verify the body has at least one shape with nonzero density, or use manual mass configuration to avoid zero-mass behavior.