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docs/engine-reference/unreal/modules/physics.md

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+# Unreal Engine 5.7 — Physics Module Reference
+
+**Last verified:** 2026-02-13
+**Knowledge Gap:** UE 5.7 Chaos Physics improvements
+
+---
+
+## Overview
+
+UE 5 uses **Chaos Physics** (replaced PhysX in UE 4):
+- Better performance
+- Destruction support
+- Vehicle physics improvements
+
+---
+
+## Rigid Body Physics
+
+### Enable Physics on Static Mesh
+
+```cpp
+UStaticMeshComponent* MeshComp = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("Mesh"));
+MeshComp->SetSimulatePhysics(true);
+MeshComp->SetEnableGravity(true);
+MeshComp->SetMassOverrideInKg(NAME_None, 50.0f); // 50 kg
+```
+
+### Apply Forces
+
+```cpp
+// Apply impulse (instant velocity change)
+MeshComp->AddImpulse(FVector(0, 0, 1000), NAME_None, true);
+
+// Apply force (continuous)
+MeshComp->AddForce(FVector(0, 0, 500));
+
+// Apply torque (rotation)
+MeshComp->AddTorqueInRadians(FVector(0, 0, 100));
+```
+
+---
+
+## Collision
+
+### Collision Channels
+
+```cpp
+// Project Settings > Engine > Collision
+// Define custom collision channels and responses
+
+// Set collision in C++
+MeshComp->SetCollisionEnabled(ECollisionEnabled::QueryAndPhysics);
+MeshComp->SetCollisionObjectType(ECollisionChannel::ECC_Pawn);
+MeshComp->SetCollisionResponseToAllChannels(ECR_Block);
+MeshComp->SetCollisionResponseToChannel(ECC_Camera, ECR_Ignore);
+```
+
+### Collision Events
+
+```cpp
+// Enable collision events
+MeshComp->SetNotifyRigidBodyCollision(true);
+
+// Bind to OnComponentHit
+MeshComp->OnComponentHit.AddDynamic(this, &AMyActor::OnHit);
+
+UFUNCTION()
+void AMyActor::OnHit(UPrimitiveComponent* HitComp, AActor* OtherActor,
+    UPrimitiveComponent* OtherComp, FVector NormalImpulse, const FHitResult& Hit) {
+    UE_LOG(LogTemp, Warning, TEXT("Hit %s"), *OtherActor->GetName());
+}
+```
+
+### Overlap Events
+
+```cpp
+// Enable overlap events
+MeshComp->SetGenerateOverlapEvents(true);
+
+// Bind to OnComponentBeginOverlap
+MeshComp->OnComponentBeginOverlap.AddDynamic(this, &AMyActor::OnOverlapBegin);
+
+UFUNCTION()
+void AMyActor::OnOverlapBegin(UPrimitiveComponent* OverlappedComp, AActor* OtherActor,
+    UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult) {
+    UE_LOG(LogTemp, Warning, TEXT("Overlapped %s"), *OtherActor->GetName());
+}
+```
+
+---
+
+## Raycasting (Line Traces)
+
+### Single Line Trace
+
+```cpp
+FHitResult HitResult;
+FVector Start = GetActorLocation();
+FVector End = Start + GetActorForwardVector() * 1000.0f;
+
+FCollisionQueryParams QueryParams;
+QueryParams.AddIgnoredActor(this);
+
+// Perform trace
+bool bHit = GetWorld()->LineTraceSingleByChannel(
+    HitResult,
+    Start,
+    End,
+    ECC_Visibility,
+    QueryParams
+);
+
+if (bHit) {
+    UE_LOG(LogTemp, Warning, TEXT("Hit: %s"), *HitResult.GetActor()->GetName());
+    DrawDebugLine(GetWorld(), Start, HitResult.Location, FColor::Red, false, 2.0f);
+}
+```
+
+### Multi Line Trace
+
+```cpp
+TArray<FHitResult> HitResults;
+bool bHit = GetWorld()->LineTraceMultiByChannel(
+    HitResults,
+    Start,
+    End,
+    ECC_Visibility,
+    QueryParams
+);
+
+for (const FHitResult& Hit : HitResults) {
+    UE_LOG(LogTemp, Warning, TEXT("Hit: %s"), *Hit.GetActor()->GetName());
+}
+```
+
+### Sweep (Thick Trace)
+
+```cpp
+FHitResult HitResult;
+FCollisionShape Sphere = FCollisionShape::MakeSphere(50.0f);
+
+bool bHit = GetWorld()->SweepSingleByChannel(
+    HitResult,
+    Start,
+    End,
+    FQuat::Identity,
+    ECC_Visibility,
+    Sphere,
+    QueryParams
+);
+```
+
+---
+
+## Character Movement
+
+### Character Movement Component
+
+```cpp
+// Built into ACharacter class
+UCharacterMovementComponent* MoveComp = GetCharacterMovement();
+
+// Configure movement
+MoveComp->MaxWalkSpeed = 600.0f;
+MoveComp->JumpZVelocity = 600.0f;
+MoveComp->AirControl = 0.2f;
+MoveComp->GravityScale = 1.0f;
+MoveComp->bOrientRotationToMovement = true;
+```
+
+### Add Movement Input
+
+```cpp
+// In Character class
+void AMyCharacter::MoveForward(float Value) {
+    if (Value != 0.0f) {
+        AddMovementInput(GetActorForwardVector(), Value);
+    }
+}
+
+void AMyCharacter::MoveRight(float Value) {
+    if (Value != 0.0f) {
+        AddMovementInput(GetActorRightVector(), Value);
+    }
+}
+```
+
+---
+
+## Physical Materials
+
+### Create Physical Material
+
+1. Content Browser > Right Click > Physics > Physical Material
+2. Configure properties:
+   - Friction: 0.0 - 1.0
+   - Restitution (bounciness): 0.0 - 1.0
+
+### Assign Physical Material
+
+```cpp
+// In static mesh editor: Physics > Phys Material Override
+// Or in C++:
+MeshComp->SetPhysMaterialOverride(PhysicalMaterial);
+```
+
+---
+
+## Constraints (Physics Joints)
+
+### Physics Constraint Component
+
+```cpp
+UPhysicsConstraintComponent* Constraint = CreateDefaultSubobject<UPhysicsConstraintComponent>(TEXT("Constraint"));
+Constraint->SetConstrainedComponents(ComponentA, NAME_None, ComponentB, NAME_None);
+
+// Configure constraint
+Constraint->SetLinearXLimit(ELinearConstraintMotion::LCM_Limited, 100.0f);
+Constraint->SetLinearYLimit(ELinearConstraintMotion::LCM_Locked, 0.0f);
+Constraint->SetLinearZLimit(ELinearConstraintMotion::LCM_Free, 0.0f);
+
+Constraint->SetAngularSwing1Limit(EAngularConstraintMotion::ACM_Limited, 45.0f);
+```
+
+---
+
+## Destruction (Chaos Destruction)
+
+### Enable Chaos Destruction
+
+```cpp
+// Plugin: Enable "Chaos" plugin
+// Create Geometry Collection asset for destructible objects
+```
+
+### Destroy Geometry Collection
+
+```cpp
+// Fracture mesh in Chaos editor
+// In game, apply damage:
+UGeometryCollectionComponent* GeoComp = /* Get component */;
+GeoComp->ApplyPhysicsField(/* Field parameters */);
+```
+
+---
+
+## Performance Tips
+
+### Physics Optimization
+
+```cpp
+// Simplify collision shapes (use simple primitives)
+MeshComp->SetCollisionEnabled(ECollisionEnabled::NoCollision); // Disable when not needed
+
+// Use Physics Asset for skeletal meshes (simplified collision)
+// Don't simulate physics for distant objects
+
+// Reduce physics substeps:
+// Project Settings > Engine > Physics > Max Substep Delta Time
+```
+
+---
+
+## Debugging
+
+### Physics Debug Visualization
+
+```cpp
+// Console commands:
+// show collision - Show collision shapes
+// p.Chaos.DebugDraw.Enabled 1 - Show Chaos debug
+// pxvis collision - Visualize collision
+
+// Draw debug shapes:
+DrawDebugSphere(GetWorld(), Location, Radius, 12, FColor::Green, false, 2.0f);
+DrawDebugBox(GetWorld(), Location, Extent, FColor::Red, false, 2.0f);
+```
+
+---
+
+## Sources
+- https://docs.unrealengine.com/5.7/en-US/physics-in-unreal-engine/
+- https://docs.unrealengine.com/5.7/en-US/chaos-physics-overview-in-unreal-engine/