Class DistanceJoint

Constrains the distance between two anchor points (one on each body) within a range.

Enforces: jointMin ≤ distance(anchor1, anchor2) ≤ jointMax

When jointMin === jointMax the distance is fixed (like a rigid rod). When jointMin < jointMax the joint acts as a slack rope / elastic band.

Anchors are specified in each body's local coordinate space.

Example

// Attach two bodies with a fixed-length rod
const joint = new DistanceJoint(
  body1, body2,
  Vec2.weak(0, 0),   // anchor on body1 (local)
  Vec2.weak(0, 0),   // anchor on body2 (local)
  50, 50,            // fixed distance
);
joint.space = space;

Fully modernized — uses ZPP_DistanceJoint directly (extracted to TypeScript).

Hierarchy (View Summary)

Constraint
- DistanceJoint

Index

Constructors

constructor

new DistanceJoint(
    body1: Body | null,
    body2: Body | null,
    anchor1: Vec2,
    anchor2: Vec2,
    jointMin: number,
    jointMax: number,
): DistanceJoint
Parameters
- body1: Body | null
  First body, or null for a static world anchor.
- body2: Body | null
  Second body, or null for a static world anchor.
- anchor1: Vec2
  Anchor point in body1's local space (disposed if weak).
- anchor2: Vec2
  Anchor point in body2's local space (disposed if weak).
- jointMin: number
  Minimum allowed distance (must be >= 0).
- jointMax: number
  Maximum allowed distance (must be >= jointMin).
Returns DistanceJoint
Overrides Constraint.constructor
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:67

Properties

debugDraw

debugDraw: boolean = true

Accessors

active

get active(): boolean
Whether the constraint is currently active (enforced by the solver).

Deactivating a constraint suspends it without removing it from the space.

Returns boolean

Default Value
true
Inherited from Constraint.active
- Defined in packages/nape-js/src/constraint/Constraint.ts:152
set active(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.active
- Defined in packages/nape-js/src/constraint/Constraint.ts:155

anchor1

get anchor1(): Vec2
Anchor point on body1 in local coordinates. Modifying this wakes the constraint.

Returns Vec2
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:244
set anchor1(value: Vec2): void
Parameters
- value: Vec2
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:250

anchor2

get anchor2(): Vec2
Anchor point on body2 in local coordinates. Modifying this wakes the constraint.

Returns Vec2
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:265
set anchor2(value: Vec2): void
Parameters
- value: Vec2
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:271

body1

get body1(): Body
First body. null treats the anchor as a static world point.

Returns Body
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:170
set body1(value: Body | null): void
Parameters
- value: Body | null
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:174

body2

get body2(): Body
Second body. null treats the anchor as a static world point.

Returns Body
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:205
set body2(value: Body | null): void
Parameters
- value: Body | null
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:209

breakUnderError

get breakUnderError(): boolean
When true, the constraint breaks if the positional error exceeds maxError.

Returns boolean

Default Value
false
Inherited from Constraint.breakUnderError
- Defined in packages/nape-js/src/constraint/Constraint.ts:328
set breakUnderError(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.breakUnderError
- Defined in packages/nape-js/src/constraint/Constraint.ts:331

breakUnderForce

get breakUnderForce(): boolean
When true, the constraint breaks (fires a BREAK event) if the applied force exceeds maxForce in a single step.

Returns boolean

Default Value
false
Inherited from Constraint.breakUnderForce
- Defined in packages/nape-js/src/constraint/Constraint.ts:314
set breakUnderForce(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.breakUnderForce
- Defined in packages/nape-js/src/constraint/Constraint.ts:317

cbTypes

get cbTypes(): object
The set of CbTypes assigned to this constraint. Used to filter which listeners respond to this constraint's events.

Returns object
Inherited from Constraint.cbTypes
- Defined in packages/nape-js/src/constraint/Constraint.ts:379

compound

get compound(): Compound | null
The compound this constraint belongs to, or null. When set, the constraint's space is managed by the compound.

Returns Compound | null
Inherited from Constraint.compound
- Defined in packages/nape-js/src/constraint/Constraint.ts:124
set compound(value: Compound | null): void
Parameters
- value: Compound | null
Returns void
Inherited from Constraint.compound
- Defined in packages/nape-js/src/constraint/Constraint.ts:128

damping

get damping(): number
Damping ratio for soft constraints (stiff = false).

0 = undamped (oscillates freely), 1 = critically damped. Values > 1 are overdamped. Must be >= 0. Ignored when stiff is true.

Returns number

Default Value
1
Inherited from Constraint.damping
- Defined in packages/nape-js/src/constraint/Constraint.ts:244
set damping(value: number): void
Parameters
- value: number
Returns void
Inherited from Constraint.damping
- Defined in packages/nape-js/src/constraint/Constraint.ts:247

frequency

get frequency(): number
Spring frequency in Hz for soft constraints (stiff = false).

Higher values make the spring stiffer; lower values make it bouncier. Must be > 0. Ignored when stiff is true.

Returns number

Default Value
10
Inherited from Constraint.frequency
- Defined in packages/nape-js/src/constraint/Constraint.ts:219
set frequency(value: number): void
Parameters
- value: number
Returns void
Inherited from Constraint.frequency
- Defined in packages/nape-js/src/constraint/Constraint.ts:222

ignore

get ignore(): boolean
When true the constraint is completely ignored by the engine — bodies are not woken, no impulse is applied, and no callbacks fire.

Returns boolean

Default Value
false
Inherited from Constraint.ignore
- Defined in packages/nape-js/src/constraint/Constraint.ts:186
set ignore(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.ignore
- Defined in packages/nape-js/src/constraint/Constraint.ts:189

isSleeping

get isSleeping(): boolean
Whether the constraint's simulation component is currently sleeping.

Only valid when the constraint is active and in a space — throws otherwise.

Returns boolean
Inherited from Constraint.isSleeping
- Defined in packages/nape-js/src/constraint/Constraint.ts:355

jointMax

get jointMax(): number
Maximum allowed distance between anchors (pixels, must be >= jointMin).

Returns number
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:308
set jointMax(value: number): void
Parameters
- value: number
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:311

jointMin

get jointMin(): number
Minimum allowed distance between anchors (pixels, must be >= 0).

Returns number
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:290
set jointMin(value: number): void
Parameters
- value: number
Returns void
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:293

maxError

get maxError(): number
Maximum positional error (in pixels) allowed before breaking.

Only meaningful when breakUnderError is true. Must be >= 0. Infinity disables the limit.

Returns number

Default Value
Infinity
Inherited from Constraint.maxError
- Defined in packages/nape-js/src/constraint/Constraint.ts:293
set maxError(value: number): void
Parameters
- value: number
Returns void
Inherited from Constraint.maxError
- Defined in packages/nape-js/src/constraint/Constraint.ts:296

maxForce

get maxForce(): number
Maximum force (in Newtons) the constraint may apply per step.

When the required force exceeds this value the constraint becomes slack. If breakUnderForce is true the constraint breaks instead. Must be >= 0. Infinity disables the limit.

Returns number

Default Value
Infinity
Inherited from Constraint.maxForce
- Defined in packages/nape-js/src/constraint/Constraint.ts:270
set maxForce(value: number): void
Parameters
- value: number
Returns void
Inherited from Constraint.maxForce
- Defined in packages/nape-js/src/constraint/Constraint.ts:273

removeOnBreak

get removeOnBreak(): boolean
When true (default), the constraint is automatically removed from its space when it breaks. Set to false to keep it in the space after breaking.

Returns boolean

Default Value
true
Inherited from Constraint.removeOnBreak
- Defined in packages/nape-js/src/constraint/Constraint.ts:343
set removeOnBreak(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.removeOnBreak
- Defined in packages/nape-js/src/constraint/Constraint.ts:346

space

get space(): Space | null
The space this constraint belongs to, or null if not in a space.

Assign to add/remove the constraint from a space:
```
joint.space = mySpace;  // adds to space
joint.space = null;     // removes from space
```
Cannot be set if the constraint belongs to a Compound.
Returns Space | null
Inherited from Constraint.space
- Defined in packages/nape-js/src/constraint/Constraint.ts:85
set space(value: Space | null): void
Parameters
- value: Space | null
Returns void
Inherited from Constraint.space
- Defined in packages/nape-js/src/constraint/Constraint.ts:89

stiff

get stiff(): boolean
When true (default) the constraint is stiff/rigid. When false the constraint uses a soft spring model driven by frequency and damping.

Returns boolean

Default Value
true
Inherited from Constraint.stiff
- Defined in packages/nape-js/src/constraint/Constraint.ts:202
set stiff(value: boolean): void
Parameters
- value: boolean
Returns void
Inherited from Constraint.stiff
- Defined in packages/nape-js/src/constraint/Constraint.ts:205

userData

get userData(): Record<string, unknown>
Arbitrary user data attached to this constraint. Lazily initialized to {} on first access.

Returns Record<string, unknown>
Inherited from Constraint.userData
- Defined in packages/nape-js/src/constraint/Constraint.ts:368

Methods

bodyImpulse

bodyImpulse(body: Body): Vec3
The impulse applied to body by this constraint in the last simulation step, expressed as a Vec3 (fx, fy, torque).
Parameters
- body: Body
Returns Vec3
Overrides Constraint.bodyImpulse
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:352

copy

copy(): Constraint
Creates and returns a copy of this constraint with the same parameters. The copy is not automatically added to a space.

Returns Constraint
Inherited from Constraint.copy
- Defined in packages/nape-js/src/constraint/Constraint.ts:422

impulse

impulse(): MatMN
The impulse applied by this constraint in the last simulation step.

The shape of the returned MatMN depends on the constraint's degrees of freedom (e.g., 1×1 for AngleJoint/MotorJoint, 2×1 for PivotJoint/LineJoint, 3×1 for WeldJoint).

Returns MatMN
Overrides Constraint.impulse
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:342

isSlack

isSlack(): boolean
Returns true when the current distance is within [jointMin, jointMax] and no corrective impulse was applied last step.

Returns boolean

Throws
if either body is null.
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:335

toString

toString(): string
Returns string
Inherited from Constraint.toString
- Defined in packages/nape-js/src/constraint/Constraint.ts:426

visitBodies

visitBodies(lambda: (body: Body) => void): void
Invokes fn once for each distinct body linked to this constraint.
Parameters
- lambda: (body: Body) => void
Returns void
Overrides Constraint.visitBodies
- Defined in packages/nape-js/src/constraint/DistanceJoint.ts:369

Class DistanceJoint

Example

Hierarchy (View Summary)

Index

Constructors

Properties

Accessors

Methods

Constructors

constructor

Parameters

Returns DistanceJoint

Properties

debugDraw

Accessors

active

Returns boolean

Default Value

Parameters

Returns void

anchor1

Returns Vec2

Parameters

Returns void

anchor2

Returns Vec2

Parameters

Returns void

body1

Returns Body

Parameters

Returns void

body2

Returns Body

Parameters

Returns void

breakUnderError

Returns boolean

Default Value

Parameters

Returns void

breakUnderForce

Returns boolean

Default Value

Parameters

Returns void

cbTypes

Returns object

compound

Returns Compound | null

Parameters

Returns void

damping

Returns number

Default Value

Parameters

Returns void

frequency

Returns number

Default Value

Parameters

Returns void

ignore

Returns boolean

Default Value

Parameters

Returns void

isSleeping

Returns boolean

jointMax

Returns number

Parameters

Returns void

jointMin

Returns number

Parameters

Returns void

maxError

Returns number

Default Value