version: "1.0.0" title: ue-physics-collision description: Use when configuring UE 5.7 collision modes, responses, overlaps, traces, sweeps, or diagnosing collision state across Actor and PrimitiveComponent layers.

UE Physics and Collision

Use this guide to reason about collision state without treating a single checkbox or function as the whole collision contract.

Separate the collision layers

Collision depends on multiple layers: the Actor-level enable flag, each UPrimitiveComponent collision mode, object type and channel responses, collision geometry, and the query/simulation being performed. Inspect all relevant layers before declaring collision enabled or disabled.

Actor-level gate

AActor::SetActorEnableCollision changes the Actor-level collision gate, and GetActorEnableCollision reads it back. This does not rewrite every component's ECollisionEnabled mode or response table.

Component collision mode

UPrimitiveComponent::SetCollisionEnabled selects query/physics participation through ECollisionEnabled::Type. SetCollisionProfileName applies a named profile. A component still needs suitable geometry and responses for the intended interaction.

Channel response

SetCollisionResponseToChannel changes one response, while SetCollisionResponseToAllChannels and SetCollisionResponseToChannels change broader response state. The other participant or query channel also matters.

// Fragment: Component and the project-defined channel are supplied elsewhere.
Component->SetCollisionEnabled(ECollisionEnabled::QueryOnly);
Component->SetCollisionResponseToChannel(ECC_Visibility, ECR_Block);

Overlap and hit notifications

Overlap generation and blocking-hit notification are separate from the response table. SetGenerateOverlapEvents controls overlap-event generation for a primitive component; physics hit notification uses the body-instance notification surface. A blocking response does not automatically mean every desired event delegate will fire.

Scene queries

UWorld exposes channel-based line traces, sweeps, and overlap queries. Use FCollisionQueryParams to ignore the querying Actor when appropriate, and inspect the returned FHitResult rather than assuming the first visible object is the collision result.

Runtime mutation boundary

After changing collision at runtime, read back the Actor/component state and run the intended query or movement scenario. A state readback proves configuration, not that geometry, paired responses, or gameplay events are correct.

Debugging checklist

• Identify the exact primitive component expected to collide.
• Record Actor gate, component mode, object type, and response to the tested channel.
• Distinguish overlap, blocking, query, and physics-simulation expectations.
• Check initial penetration and the movement/query shape.
• Use a focused Automation test for any behavior claimed as verified.

Focused references

• Trace patterns
• Actor collision enable state
• Collision channel setup
• Ground penetration debugging
• Runtime collision refresh