Collision

Functions for colliding pairs of shapes. More...

Data Structures
struct	b2ManifoldPoint
	A manifold point is a contact point belonging to a contact manifold. More...
struct	b2Manifold
	A contact manifold describes the contact points between colliding shapes. More...

Functions
b2Manifold	b2CollideCircles (const b2Circle *circleA, b2Transform xfA, const b2Circle *circleB, b2Transform xfB)
	Compute the contact manifold between two circles.
b2Manifold	b2CollideCapsuleAndCircle (const b2Capsule *capsuleA, b2Transform xfA, const b2Circle *circleB, b2Transform xfB)
	Compute the contact manifold between a capsule and circle.
b2Manifold	b2CollideSegmentAndCircle (const b2Segment *segmentA, b2Transform xfA, const b2Circle *circleB, b2Transform xfB)
	Compute the contact manifold between an segment and a circle.
b2Manifold	b2CollidePolygonAndCircle (const b2Polygon *polygonA, b2Transform xfA, const b2Circle *circleB, b2Transform xfB)
	Compute the contact manifold between a polygon and a circle.
b2Manifold	b2CollideCapsules (const b2Capsule *capsuleA, b2Transform xfA, const b2Capsule *capsuleB, b2Transform xfB)
	Compute the contact manifold between a capsule and circle.
b2Manifold	b2CollideSegmentAndCapsule (const b2Segment *segmentA, b2Transform xfA, const b2Capsule *capsuleB, b2Transform xfB)
	Compute the contact manifold between an segment and a capsule.
b2Manifold	b2CollidePolygonAndCapsule (const b2Polygon *polygonA, b2Transform xfA, const b2Capsule *capsuleB, b2Transform xfB)
	Compute the contact manifold between a polygon and capsule.
b2Manifold	b2CollidePolygons (const b2Polygon *polygonA, b2Transform xfA, const b2Polygon *polygonB, b2Transform xfB)
	Compute the contact manifold between two polygons.
b2Manifold	b2CollideSegmentAndPolygon (const b2Segment *segmentA, b2Transform xfA, const b2Polygon *polygonB, b2Transform xfB)
	Compute the contact manifold between an segment and a polygon.
b2Manifold	b2CollideChainSegmentAndCircle (const b2ChainSegment *segmentA, b2Transform xfA, const b2Circle *circleB, b2Transform xfB)
	Compute the contact manifold between a chain segment and a circle.
b2Manifold	b2CollideChainSegmentAndCapsule (const b2ChainSegment *segmentA, b2Transform xfA, const b2Capsule *capsuleB, b2Transform xfB, b2SimplexCache *cache)
	Compute the contact manifold between a chain segment and a capsule.
b2Manifold	b2CollideChainSegmentAndPolygon (const b2ChainSegment *segmentA, b2Transform xfA, const b2Polygon *polygonB, b2Transform xfB, b2SimplexCache *cache)
	Compute the contact manifold between a chain segment and a rounded polygon.

Detailed Description

Functions for colliding pairs of shapes.

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Data Structure Documentation

b2ManifoldPoint

struct b2ManifoldPoint

A manifold point is a contact point belonging to a contact manifold.

It holds details related to the geometry and dynamics of the contact points. Box2D uses speculative collision so some contact points may be separated. You may use the totalNormalImpulse to determine if there was an interaction during the time step.

Collaboration diagram for b2ManifoldPoint:

Data Fields
b2Vec2	anchorA	Location of the contact point relative to shapeA's origin in world space. Note When used internally to the Box2D solver, this is relative to the body center of mass.
b2Vec2	anchorB	Location of the contact point relative to shapeB's origin in world space. Note When used internally to the Box2D solver, this is relative to the body center of mass.
uint16_t	id	Uniquely identifies a contact point between two shapes.
float	normalImpulse	The impulse along the manifold normal vector.
float	normalVelocity	Relative normal velocity pre-solve. Used for hit events. If the normal impulse is zero then there was no hit. Negative means shapes are approaching.
bool	persisted	Did this contact point exist the previous step?
b2Vec2	point	Location of the contact point in world space. Subject to precision loss at large coordinates. Note Should only be used for debugging.
float	separation	The separation of the contact point, negative if penetrating.
float	tangentImpulse	The friction impulse.
float	totalNormalImpulse	The total normal impulse applied across sub-stepping and restitution. This is important to identify speculative contact points that had an interaction in the time step.

b2Manifold

struct b2Manifold

A contact manifold describes the contact points between colliding shapes.

Note

Box2D uses speculative collision so some contact points may be separated.

Collaboration diagram for b2Manifold:

Data Fields
b2Vec2	normal	The unit normal vector in world space, points from shape A to bodyB.
int	pointCount	The number of contacts points, will be 0, 1, or 2.
b2ManifoldPoint	points[2]	The manifold points, up to two are possible in 2D.
float	rollingImpulse	Angular impulse applied for rolling resistance. N * m * s = kg * m^2 / s.