Physics & collision (Chaos)

Chaos is the physics engine in UE. Most gameplay needs three things from it: collision (what blocks/overlaps what), queries (traces/sweeps to ask about the world), and occasionally simulation (rigid bodies, ragdolls, constraints). Collision setup mistakes are the most common source of "my overlap/hit never fires" bugs.

When to use this skill

• Setting up what collides with what (channels, presets, per-channel responses).
• Making trigger volumes or detecting overlaps between actors.
• Line/shape tracing the world (aiming, ground checks, interaction detection).
• Simulating physics objects — enabling rigid-body physics, applying forces/impulses.
• Building ragdolls or constraining bodies with UPhysicsConstraintComponent.
• Debugging "overlap never fires", "trace misses", or "physics not simulating" problems.

Collision model — three controls per component

Every UPrimitiveComponent has three collision controls: