Collision Parameters

Parameters related to collision detection.

About This Page

This is the complete reference for collision parameters. For the actual setup steps and how to choose shapes, see the Collision Setup guide; for sharing collision across multiple meshes, see Shared Collision.

Collision Types

KawaiiPhysics supports the following 4 collision shapes.

Type	Description
Spherical	Sphere collision
Capsule	Capsule collision
Box	Box collision
Planar	Plane collision

FCollisionLimitBase (Common Properties)

Base properties common to all collision types.

Property	Type	Description
DrivingBone	FBoneReference	Bone that the collision follows
OffsetLocation	FVector	Offset position from bone (Default: ZeroVector)
OffsetRotation	FRotator	Offset rotation from bone (Default: ZeroRotator, Range: -360 to 360)

FSphericalLimit (Sphere Collision)

Adds spherical collision detection.

UPROPERTY(EditAnywhere, Category = "Limits")
TArray<FSphericalLimit> SphericalLimits;

Properties

Name	Type	Default	Description
Radius	float	5.0	Sphere radius (0 or higher)
LimitType	ESphericalLimitType	Outer	Inner/outer limit type

ESphericalLimitType

Value	Description
Inner	Limit to inside the sphere (push bone inside the sphere)
Outer	Limit to outside the sphere (push bone out of the sphere)

FCapsuleLimit (Capsule Collision)

Adds capsule-shaped collision detection.

UPROPERTY(EditAnywhere, Category = "Limits")
TArray<FCapsuleLimit> CapsuleLimits;

Properties

Name	Type	Default	Description
Radius	float	5.0	Capsule radius (0 or higher)
Length	float	10.0	Capsule length (0 or higher)

FTaperedCapsuleLimit (Tapered Capsule)

Not officially released

This feature has not been officially released yet. It is planned for KawaiiPhysics v1.22. Specifications may change during development.

FTaperedCapsuleLimit represents a collision shape with a different radius at each end. In addition to Simple World Collision gathering, it is supported by the node's Collision > Tapered Capsule Collision, Limits DataAssets, and shapes read from PhysicsAssets. Ordinary Capsules existed before v1.22; separate endpoint-radius support is the addition described here.

Setting	Default	Meaning
Radius0	5 cm	Radius at the shape-local +Z endpoint
Radius1	5 cm	Radius at the shape-local −Z endpoint
Length	10 cm	Distance between endpoint sphere centers, not overall length

Position it with Driving Bone and location/rotation offsets. Equal endpoint radii give an equal-radius capsule. Radii and length are clamped to nonnegative values. When Length <= abs(Radius0 - Radius1) (with a small tolerance in the implementation), the smaller endpoint sphere is contained in the larger one, and the shape collapses to that larger sphere. Collision, editing, and debug drawing use the same condition.

In the normal case, push-out linearly interpolates the radius at the closest point on the axis segment. This does not guarantee identical contacts to Chaos geometry, so test strong tapers and narrow parts in practice. Simple World Collision conversion uses query-enabled shapes and does not use cloth Width or one-sided collision attributes. Mirror Data Table for Collision swaps radii when needed to preserve endpoint meaning.

Setup steps and diagram

FBoxLimit (Box Collision)

Adds box-shaped collision detection.

UPROPERTY(EditAnywhere, Category = "Limits")
TArray<FBoxLimit> BoxLimits;

Properties

Name	Type	Default	Description
Extent	FVector	(5.0, 5.0, 5.0)	Box extent (half size for each axis)

FPlanarLimit (Plane Collision)

Adds planar collision detection.

UPROPERTY(EditAnywhere, Category = "Limits")
TArray<FPlanarLimit> PlanarLimits;

Properties

Name	Type	Default	Description
Plane	FPlane	(0, 0, 0, 0)	Plane definition

Loading from Data Asset

LimitsDataAsset

Collision settings can be loaded from a Data Asset. Recommended when you want to reuse settings across different AnimNodes or Animation Blueprints.

UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Limits")
TObjectPtr<UKawaiiPhysicsLimitsDataAsset> LimitsDataAsset;

PhysicsAssetForLimits

Collision settings can also be loaded from a Physics Asset.

UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Limits")
TObjectPtr<UPhysicsAsset> PhysicsAssetForLimits;

World Collision

bAllowWorldCollision

World Collision - Flag to perform collision detection with collisions in the level.

Property	Value
Type	bool
Default	false

warning

Enabling this significantly increases physics processing load.

bIgnoreSelfComponent

Ignore Self Collision - Flag to ignore collisions (PhysicsAsset) owned by the SkeletalMeshComponent in WorldCollision.

Property	Value
Type	bool
Default	true
Edit Condition	bAllowWorldCollision == true

IgnoreBones

Ignore Bones - Setting to ignore collisions (PhysicsAsset) owned by the SkeletalMeshComponent in WorldCollision (specified by bones).

Property	Value
Type	TArray<FBoneReference>
Edit Condition	bIgnoreSelfComponent == false

IgnoreBoneNamePrefix

Ignore Bone Name Prefix - Setting to ignore collisions (PhysicsAsset) owned by the SkeletalMeshComponent in WorldCollision (specified by bone name prefix).

Property	Value
Type	TArray<FName>
Edit Condition	bIgnoreSelfComponent == false

bOverrideCollisionParams

Override Collision Parameters - Set when using custom collision settings instead of SkeletalMeshComponent's collision settings for WorldCollision.

Property	Value
Type	bool
Default	false

Shared Collision

Settings that let multiple KawaiiPhysics nodes share a single set of collision shapes. Collision can be shared across different meshes within the same Actor/ChildActor family. See Shared Collision for details.

bSharedCollisionSource

Publish Collision - Provides this node's collision to KawaiiPhysics nodes in the same attached Actor/ChildActor family (acts as a Source).

Property	Value
Type	bool
Default	false
Category	Limits|Shared Collision

bUseSharedCollision

Use Shared Collision - Uses collision published by Source nodes in the same family (acts as a Target). Mutually exclusive with Source.

Property	Value
Type	bool
Default	false
Edit Condition	!bSharedCollisionSource
Category	Limits|Shared Collision

SharedCollisionGroupTag

Group Tag - A GameplayTag identifying the shared collision group. Both Source and Target use the same tag.

Property	Value
Type	FGameplayTag
Edit Condition	bSharedCollisionSource || bUseSharedCollision
Category	Limits|Shared Collision

tip

To use same-frame collision within one AnimGraph, place the Source node so it evaluates before the Target node.

Collision Source Type

Enum indicating the source of collision settings.

UENUM()
enum class ECollisionSourceType : uint8
{
    AnimNode,      // Use values set in AnimNode
    DataAsset,     // Use values set in DataAsset
    PhysicsAsset,  // Use values set in PhysicsAsset
};

tip

Using Data Assets allows sharing collision settings across multiple AnimNodes and Animation Blueprints.

For more details, see Data Assets.

Related UE documentation

• Physics Asset Editor — Understand PhysicsAssets and the editor used to author their shapes. (UE 5.8)