Class Joints2D

Namespace

Stride.CommunityToolkit.Box2D

Assembly

Stride.CommunityToolkit.Box2D.dll

Box2D's seven joint types with world-space anchors: say where the pivot is and which way the axis points, and the local frames each body needs are worked out here.

public static class Joints2D

Inheritance

object

Joints2D

Remarks

A raw joint definition hides its bodies inside a base field and expresses each anchor as a local frame: a point and a rotation in that body's own space, which have to be derived from the world pivot with the body's current transform. Every Box2D sample repeats that derivation; these factories do it once. The pose at creation is the joint's zero: a revolute joint's angle, a prismatic joint's translation and a weld's rest pose are all measured from where the bodies were when the joint was made.

Options records carry the per-type knobs by the names Box2D uses. A property left null keeps Box2D's default, so new RevoluteJointOptions { EnableMotor = true, MotorSpeed = 2 } changes exactly two things. Angles are in radians, as in Box2D.

The static methods take a Box2D.NET.B2WorldId and body ids, like PhysicsQueries2D; Joints offers the same with entities.

Methods

CreateDistance(B2WorldId, B2BodyId, B2BodyId, Vector2, Vector2, DistanceJointOptions?)

A rod between two anchors, one on each body. The rest length defaults to their distance at creation; a spring makes it soft, a limit with a spring makes it a rope.

public static B2JointId CreateDistance(B2WorldId world, B2BodyId a, B2BodyId b, Vector2 worldAnchorA, Vector2 worldAnchorB, DistanceJointOptions? options = null)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

worldAnchorA Vector2

worldAnchorB Vector2

options DistanceJointOptions

Returns

B2JointId

CreateFilter(B2WorldId, B2BodyId, B2BodyId)

No constraint at all: the two bodies simply never collide with each other. For the links of a chain or the parts of a ragdoll.

public static B2JointId CreateFilter(B2WorldId world, B2BodyId a, B2BodyId b)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

Returns

B2JointId

CreateMotor(B2WorldId, B2BodyId, B2BodyId, Vector2?, MotorJointOptions?)

Drives b relative to a. With a pivot, both frames sit there and the spring pulls that point on B toward that point on A - the mouse-drag shape; without one, the frames are the body origins.

public static B2JointId CreateMotor(B2WorldId world, B2BodyId a, B2BodyId b, Vector2? worldPivot = null, MotorJointOptions? options = null)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

worldPivot Vector2?

options MotorJointOptions

Returns

B2JointId

CreatePrismatic(B2WorldId, B2BodyId, B2BodyId, Vector2, Vector2, PrismaticJointOptions?)

A slider: b moves along worldAxis through worldPivot, fixed in a's frame, without turning.

public static B2JointId CreatePrismatic(B2WorldId world, B2BodyId a, B2BodyId b, Vector2 worldPivot, Vector2 worldAxis, PrismaticJointOptions? options = null)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

worldPivot Vector2

worldAxis Vector2

options PrismaticJointOptions

Returns

B2JointId

CreateRevolute(B2WorldId, B2BodyId, B2BodyId, Vector2, RevoluteJointOptions?)

A hinge at worldPivot: the bodies turn about it and nothing else.

public static B2JointId CreateRevolute(B2WorldId world, B2BodyId a, B2BodyId b, Vector2 worldPivot, RevoluteJointOptions? options = null)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

worldPivot Vector2

options RevoluteJointOptions

Returns

B2JointId

CreateWeld(B2WorldId, B2BodyId, B2BodyId, Vector2, WeldJointOptions?)

Glues the bodies together at worldPivot in their current relative pose.

public static B2JointId CreateWeld(B2WorldId world, B2BodyId a, B2BodyId b, Vector2 worldPivot, WeldJointOptions? options = null)

Parameters

world B2WorldId

a B2BodyId

b B2BodyId

worldPivot Vector2

options WeldJointOptions

Returns

B2JointId

CreateWheel(B2WorldId, B2BodyId, B2BodyId, Vector2, Vector2, WheelJointOptions?)

A wheel on a suspension: wheel turns about worldPivot and slides along worldAxis - the suspension direction, usually straight up - relative to chassis.

public static B2JointId CreateWheel(B2WorldId world, B2BodyId chassis, B2BodyId wheel, Vector2 worldPivot, Vector2 worldAxis, WheelJointOptions? options = null)

Parameters

world B2WorldId

chassis B2BodyId

wheel B2BodyId

worldPivot Vector2

worldAxis Vector2

options WheelJointOptions

Returns

B2JointId

Destroy(B2JointId, bool)

Removes a joint. Safe on a joint that is already gone.

public static void Destroy(B2JointId joint, bool wakeBodies = true)

Parameters

joint B2JointId

The joint.

wakeBodies bool

Wake the bodies it connected, so they react to being freed.

GetAnchors(B2JointId)

The joint's two anchors in world space right now, for drawing it. They coincide for a hinge or a weld and sit apart for a rod.

public static (Vector2 A, Vector2 B) GetAnchors(B2JointId joint)

Parameters

joint B2JointId

Returns

(Vector2 A, Vector2 B)

IsValid(B2JointId)

Whether the joint still exists - it goes when either body is destroyed.

public static bool IsValid(B2JointId joint)

Parameters

joint B2JointId

Returns

bool