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...
struct	b2LocalManifoldPoint
	Contact manifold point in local coordinates (frame A). More...
struct	b2LocalManifold
	Contact manifold in local coordinates (frame A). More...

Functions
b2LocalManifold	b2CollideCircles (const b2Circle circleA, const b2Circle circleB, b2Transform xf)
	Compute the contact manifold between two circles.
b2LocalManifold	b2CollideCapsuleAndCircle (const b2Capsule capsuleA, const b2Circle circleB, b2Transform xf)
	Compute the contact manifold between a capsule and circle.
b2LocalManifold	b2CollideSegmentAndCircle (const b2Segment segmentA, const b2Circle circleB, b2Transform xf)
	Compute the contact manifold between a segment and a circle.
b2LocalManifold	b2CollidePolygonAndCircle (const b2Polygon polygonA, const b2Circle circleB, b2Transform xf)
	Compute the contact manifold between a polygon and a circle.
b2LocalManifold	b2CollideCapsules (const b2Capsule capsuleA, const b2Capsule capsuleB, b2Transform xf)
	Compute the contact manifold between two capsules.
b2LocalManifold	b2CollideSegmentAndCapsule (const b2Segment segmentA, const b2Capsule capsuleB, b2Transform xf)
	Compute the contact manifold between a segment and a capsule.
b2LocalManifold	b2CollidePolygonAndCapsule (const b2Polygon polygonA, const b2Capsule capsuleB, b2Transform xf)
	Compute the contact manifold between a polygon and capsule.
b2LocalManifold	b2CollidePolygons (const b2Polygon polygonA, const b2Polygon polygonB, b2Transform xf)
	Compute the contact manifold between two polygons.
b2LocalManifold	b2CollideSegmentAndPolygon (const b2Segment segmentA, const b2Polygon polygonB, b2Transform xf)
	Compute the contact manifold between a segment and a polygon.
b2LocalManifold	b2CollideChainSegmentAndCircle (const b2ChainSegment segmentA, const b2Circle circleB, b2Transform xf)
	Compute the contact manifold between a chain segment and a circle.
b2LocalManifold	b2CollideChainSegmentAndCapsule (const b2ChainSegment segmentA, const b2Capsule capsuleB, b2Transform xf, b2SimplexCache *cache)
	Compute the contact manifold between a chain segment and a capsule.
b2LocalManifold	b2CollideChainSegmentAndPolygon (const b2ChainSegment segmentA, const b2Polygon polygonB, b2Transform xf, b2SimplexCache *cache)
	Compute the contact manifold between a chain segment and a rounded polygon.

Detailed Description

Functions for colliding pairs of shapes.

Each function takes the shapes in their own local frames and the transform of shape B in shape A's frame (b2InvMulWorldTransforms( worldA, worldB )). The manifold is returned in frame A.

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.

Data Fields
b2Vec2	anchorA	Location of the contact point relative to bodyA's center of mass in world space. This can be converted to a world point using: b2Pos worldPointA = b2OffsetPos(b2Body_GetWorldCenter(myBodyIdA), anchorA);
b2Vec2	anchorB	Similar for body B.
float	baseSeparation	Cached separation used for contact recycling.
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. Negative when approaching. This is only computed if hit events are enabled. It may be computed otherwise as a side effect of SIMD bundling, but that is not guaranteed.
bool	persisted	Did this contact point exist the previous step?
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. This includes the warm starting impulse, the sub-step delta impulse, and the restitution impulse.

◆ 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.

Data Fields
b2Vec2	normal	The unit normal vector in world space, points from shape A to shape B.
int	pointCount	The number of contact 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.

◆ b2LocalManifoldPoint

struct b2LocalManifoldPoint

Contact manifold point in local coordinates (frame A).

Data Fields
uint16_t	id	Uniquely identifies a contact point between two shapes.
b2Vec2	point	Contact point in frame A.
float	separation	The separation of the contact point, negative if penetrating. May be positive or negative.

◆ b2LocalManifold

struct b2LocalManifold

Contact manifold in local coordinates (frame A).

Data Fields
b2Vec2	normal	The unit normal vector in frame A, points from shape A to shape B.
int	pointCount	The number of contact points, will be 0, 1, or 2.
b2LocalManifoldPoint	points[2]	The manifold points, up to two are possible in 2D.