Unreal's physics system is driven by components and collision settings on actors. A Static Mesh component can be configured with Simulate Physics enabled to participate in rigid-body simulation. Physics simulation can also be toggled at runtime through Blueprint nodes like Set Simulate Physics. A Physical Material asset, created from the Content Browser under Physics, exposes Friction, Restitution, Density, and related values, and is applied to a mesh through the Phys Material Override property. Collision Channels define how actors interact with each other during queries and trace tests; Unreal provides defaults like Visibility, Camera, Pawn, and WorldStatic alongside customizable Object and Trace channels.
Collision responses are controlled by the Collision Enabled setting on a component, which can be No Collision, Query Only (overlaps and traces but no physical blocking), Physics Only (physical blocking but no queries), or Query and Physics for full interaction. Static Mesh assets expose both Simple collision (fast primitives such as spheres or boxes) and Complex collision (the actual triangle mesh), with trade-offs between speed and accuracy. The Set Collision Enabled node changes collision response at runtime, useful for toggling actors between solid and passable states. To detect collisions in Blueprint, enable Simulation Generates Hit Events and bind OnComponentHit or OnComponentBeginOverlap events on the relevant component to receive execution pins and information about the other actor.
For more advanced setups, Physics Constraint Components and Actors connect two physics-simulating components with rules such as distance limits, angular limits, and motors. They are widely used for ragdolls, doors, chains, and jointed mechanical assemblies. A Trigger Box or any primitive with a Collision Preset of OverlapAll is the standard way to react when actors enter or exit a region: in its Blueprint, OnActorBeginOverlap and OnActorEndOverlap provide the event entry points. The CharacterMovementComponent provides walking, running, jumping, falling, swimming, and flying built atop capsule collision, handling slope limits, step height, gravity, and network prediction. To make a Character Blueprint jump, an input action is mapped to spacebar, the Pressed event calls Jump, and Released calls StopJumping.