Physics Bodies Reference

Physics Body, or Body Instance, property reference.

This page contains a reference listing of properties in the Physics and Collision categories of properties. If you are looking for reference on Collision Responses or Collision Presets please see: Collision Response Reference.

Properties

Below are the properties for Physics Bodies (Body Instances) separated by major category.

Physics

Physics body details panel showing the physics properties

Property

Description

Double Sided Geometry

If enabled, the physics triangle mesh will use double-sided faces when doing scene queries. This is useful for planes and single-sided meshes that need traces to work on both sides.

Simple Collision Physical Material

Physical material to use for simple collision on this body. Encodes information about density, friction, and so on.

Physics Type

  • Simulated: Object will use physics simulation.

  • Kinematic: Object will not be affected by physics, but can interact with physically simulated bodies.

  • Default: Object will inherit from OwnerComponent's behavior.

Mass in KG

Mass of the body in KG.

Linear Damping

'Drag' force added to reduce linear movement.

Angular Damping

'Drag' force added to reduce angular movement.

Enable Gravity

If the object should have the force of gravity applied.

Advanced

Physics body details panel showing the advanced physics properties

Property

Description

Start Awake

If the object should start awake, or if it should initially be sleeping.

Center Of Mass Offset

User specified offset for the center of mass of this object, from the calculated location.

Mass Scale

Per-instance scaling of mass.

Max Angular Velocity

The maximum angular velocity for this instance.

Sleep Family

The set of values used in considering when to put this body to sleep. Normal, Sensitive, Custom.

Inertia Tensor Scale

Per-instance scaling of inertia (larger values mean more difficulty rotating)

Walkable Slope Override

Custom walkable slope setting for this body.

See the Walkable Slope documentation for usage information.

Walkable Slope Behavior

Behavior of this surface (whether we affect the walkable slope).

Walkable Slope Angle

Override a walkable slope, applying the rules of the Walkable Slope Behavior.

Custom Sleep Threshold Multiplier

If the Sleep Family is set to Custom, multiply the natural sleep threshold by this amount. A higher number will cause the body to sleep sooner.

Stabilization Threshold Multiplier

The stabilization factor for this body if Physics stabilization is enabled. A higher number will cause more aggressive stabilization at the risk of loss of momentum at low speeds. A value of 0 will disable stabilization for this body.

Update Mass when Scale Changes

If true, it will update the mass when the scale changes.

Generate Wake Events

Determines whether 'wake/sleep' events should fire when this object is woken up or put to sleep by the physics simulation.

Collision

Physics body details panel showing the collision properties

Property

Description

Never Needs Cooked Collision Data

To do chaos this is to opt out of CreatePhysicsMeshes for certain meshes. Better a long term mesh is not to call CreatePhysicsMesh until is known there is a mesh instance that needs it.

Collision Complexity

Collision Trace behavior - by default, it will keep simple (convex) and complex (per-poly) separate.

Collision Responses

See the Collision Response Reference documentation for more information.

Simulation Generates Hit Events

Should 'Hit' events fire when this object collides during physics simulation.

Phys Material Override

Allows you to override the PhysicalMaterial to use for simple collision on this body.

Advanced

Physics body details panel showing the advanced collision properties

Property

Description

Use CCD

If true Continuous Collision Detection (CCD) will be used for this component

Ignore Analytic Collisions

If true, ignore analytic collisions and treat objects as a general implicit surface.

Smooth Edge Collisions

Remove unnecessary edge collisions to allow smooth sliding over surfaces composed of multiple actors/components.

Body Setup

Physics body details panel showing the body set up properties

Property

Description

Skip Scale from Animation

If true, scale changes from animation are ignored. This is useful for subtle scale animations like breathing where the physics collision should remain unchanged.

Primitives

Simplified collision representation of this object.

Spheres

Sphere Elements

Boxes

Box Elements

Capsules

Sphyl Elements

Convex Elements

Convex Elements

Tapered Capsules

Tapered Capsule Elements

Consider for Bounds

Determines whether this BodySetup should be considered for the bounding box of the PhysicsAsset (and hence SkeletalMeshComponent). There is a speed improvement from having fewer BodySetups processed each frame when updating the bounds.

Bone Name

Used in the PhysicsAsset case. Associates this Body with a Bone in a skeletal mesh.

See below for the Detail properties for each Primitive type.

Primitive Types

Spheres

Body setup details for sphere primitives

Property

Description

Center

Position of the sphere's origin.

Radius

Radius of the sphere.

Rest Offset

The offset used when generating contact points. This allows you to smooth out the Minkowski sum by radius R. Useful for making objects slide smoothly on top of irregularities.

Name

User-defined name for this shape.

Contribute to Mass

Enable if this shape should contribute to the overall mass of the body it belongs to. This lets you create extra collision volumes which do not affect the mass properties of an object.

Collision Enabled

Course per-primitive collision filtering. This allows for individual primitives to be toggled in and out of sim and query collisions without changing filtering details.

Boxes

Body setup details for box primitives

Property

Description

Center

Position of the box's origin.

Rotation

Rotation of the box, in degrees around each axis.

X Extent

Extent of the box along the x-axis.

Y Extent

Extent of the box along the y-axis.

Z Extent

Extent of the box along the z-axis.

Rest Offset

The offset used when generating contact points. This allows you to smooth out the Minkowski sum by radius R. Useful for making objects slide smoothly on top of irregularities.

Name

User-defined name for this shape.

Contribute to Mass

Enable if this shape should contribute to the overall mass of the body it belongs to. This lets you create extra collision volumes which do not affect the mass properties of an object.

Collision Enabled

Course per-primitive collision filtering. This allows for individual primitives to be toggled in and out of sim and query collisions without changing filtering details.

Capsules

Body setup details for capsule primitives

Property

Description

Center

Position of the capsule's origin.

Rotation

Rotation of the capsule, in degrees around each axis.

Radius

Radius of the capsule

Length

The length of the line-segment. Add Radius to both ends to find the total length.

Rest Offset

The offset used when generating contact points. This allows you to smooth out the Minkowski sum by radius R. Useful for making objects slide smoothly on top of irregularities.

Name

User-defined name for this shape.

Contribute to Mass

Enable if this shape should contribute to the overall mass of the body it belongs to. This lets you create extra collision volumes which do not affect the mass properties of an object.

Collision Enabled

Course per-primitive collision filtering. This allows for individual primitives to be toggled in and out of sim and query collisions without changing filtering details.

Convex Elements

Body setup details for convex element primitives

Property

Description

Rest Offset

The offset used when generating contact points. This allows you to smooth out the Minkowski sum by radius R. Useful for making objects slide smoothly on top of irregularities.

Name

User-defined name for this shape.

Contribute to Mass

Enable if this shape should contribute to the overall mass of the body it belongs to. This lets you create extra collision volumes which do not affect the mass properties of an object.

Collision Enabled

Course per-primitive collision filtering. This allows for individual primitives to be toggled in and out of sim and query collisions without changing filtering details.

Tapered Capsules

Body setup details for tapered capsule primitives

Property

Description

Center

Position of the capsule's origin.

Rotation

Rotation of the capsule, in degrees around each axis.

Radius 0

Radius of the capsule start point.

Radius 1

Radius of the capsule end point.

Length

Length of the line-segment. Add Radius 0 and Radius 1 to find the total length.

Rest Offset

The offset used when generating contact points. This allows you to smooth out the Minkowski sum by radius R. Useful for making objects slide smoothly on top of irregularities.

Name

User-defined name for this shape.

Contribute to Mass

Enable if this shape should contribute to the overall mass of the body it belongs to. This lets you create extra collision volumes which do not affect the mass properties of an object.

Collision Enabled

Course per-primitive collision filtering. This allows for individual primitives to be toggled in and out of sim and query collisions without changing filtering details.