Shape Collision

Collide pairs of shapes. More...

Data Structures
struct	b3ManifoldPoint
	A manifold point is a contact point belonging to a contact manifold. More...
struct	b3Manifold
	A contact manifold describes the contact points between colliding shapes. More...
struct	b3SATCache
	Separating axis test cache. Provides temporal acceleration of collision routines. More...
struct	b3FeaturePair
	Contact points are always the result of two edges intersecting. More...
struct	b3LocalManifoldPoint
	A local manifold point and normal in frame A. More...
struct	b3LocalManifold
	A local manifold with no dynamic information. Used by b3Collide functions. More...

Enumerations
enum	b3SeparatingFeature {   b3_invalidAxis = 0 , b3_backsideAxis , b3_faceAxisA , b3_faceAxisB ,   b3_edgePairAxis , b3_closestPointsAxis , b3_manualFaceAxisA , b3_manualFaceAxisB ,   b3_manualEdgePairAxis }
	Cached separating axis feature. More...
enum	b3TriangleFeature {   b3_featureNone = 0 , b3_featureTriangleFace , b3_featureHullFace , b3_featureEdge1 ,   b3_featureEdge2 , b3_featureEdge3 , b3_featureVertex1 , b3_featureVertex2 ,   b3_featureVertex3 }
	Cached triangle feature. More...

Functions
void	b3CollideSpheres (b3LocalManifold *manifold, int capacity, const b3Sphere *sphereA, const b3Sphere *sphereB, b3Transform transformBtoA)
	Collide two spheres.
void	b3CollideCapsuleAndSphere (b3LocalManifold *manifold, int capacity, const b3Capsule *capsuleA, const b3Sphere *sphereB, b3Transform transformBtoA)
	Collide a capsule and a sphere.
void	b3CollideHullAndSphere (b3LocalManifold *manifold, int capacity, const b3HullData *hullA, const b3Sphere *sphereB, b3Transform transformBtoA, b3SimplexCache *cache)
	Collide a hull and a sphere.
void	b3CollideCapsules (b3LocalManifold *manifold, int capacity, const b3Capsule *capsuleA, const b3Capsule *capsuleB, b3Transform transformBtoA)
	Collide two capsules.
void	b3CollideHullAndCapsule (b3LocalManifold *manifold, int capacity, const b3HullData *hullA, const b3Capsule *capsuleB, b3Transform transformBtoA, b3SimplexCache *cache)
	Collide a hull and a capsule.
void	b3CollideHulls (b3LocalManifold *manifold, int capacity, const b3HullData *hullA, const b3HullData *hullB, b3Transform transformBtoA, b3SATCache *cache)
	Collide two hulls.
void	b3CollideCapsuleAndTriangle (b3LocalManifold *manifold, int capacity, const b3Capsule *capsuleA, const b3Vec3 *triangleB, b3SimplexCache *cache)
	Collide a capsule and a triangle.
void	b3CollideHullAndTriangle (b3LocalManifold *manifold, int capacity, const b3HullData *hullA, b3Vec3 v1, b3Vec3 v2, b3Vec3 v3, int triangleFlags, b3SATCache *cache)
	Collide a hull and a triangle.
void	b3CollideSphereAndTriangle (b3LocalManifold *manifold, int capacity, const b3Sphere *sphereA, const b3Vec3 *triangleB)
	Collide a sphere and a triangle.

Detailed Description

Collide pairs of shapes.

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Data Structure Documentation

b3ManifoldPoint

struct b3ManifoldPoint

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. Box3D uses speculative collision so some contact points may be separated. You may use the maxNormalImpulse to determine if there was an interaction during the time step.

Collaboration diagram for b3ManifoldPoint:

Data Fields
b3Vec3	anchorA	Location of the contact point relative to the bodyA center of mass in world space.
b3Vec3	anchorB	Location of the contact point relative to the bodyB center of mass in world space.
float	baseSeparation	Cached separation used for contact recycling.
uint32_t	featureId	Local point for matching Uniquely identifies a contact point between two shapes.
float	normalImpulse	The impulse along the manifold normal vector. Since Box3D uses sub-stepping, this is result from the final sub-step.
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 in the previous step?
float	separation	The separation of the contact point, negative if penetrating.
float	totalNormalImpulse	The total normal impulse applied during sub-stepping. This is important to identify speculative contact points that had an interaction in the time step.
int	triangleIndex	Triangle index if one of the shapes is a mesh or height field.

b3Manifold

struct b3Manifold

A contact manifold describes the contact points between colliding shapes.

Note

Box3D uses speculative collision so some contact points may be separated.

Collaboration diagram for b3Manifold:

Data Fields
b3Vec3	frictionImpulse	Central friction linear impulse.
b3Vec3	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 to 4.
b3ManifoldPoint	points[B3_MAX_MANIFOLD_POINTS]	The manifold points. There may be 1 to 4 valid points.
b3Vec3	rollingImpulse	Rolling resistance angular impulse.
float	twistImpulse	Central friction angular impulse (applied about the normal).

b3SATCache

struct b3SATCache

Separating axis test cache. Provides temporal acceleration of collision routines.

Data Fields
uint8_t	hit	Was the cache re-used?
uint8_t	indexA	Index of the feature on shape A.
uint8_t	indexB	Index of the feature on shape B.
float	separation	The separation when the cache is populated. Negative for overlap.
uint8_t	type	b3SeparatingFeature.

b3FeaturePair

struct b3FeaturePair

Contact points are always the result of two edges intersecting.

It can be two edges of the same shape, which is just a shape vertex. Or a contact point can be the result of two edges crossing from different shapes. This is designed to support hull versus hull, but it is adapted to work with all shape types. The feature pair is used to identify contact points for temporal coherence and warm starting.

Data Fields
uint8_t	index1	Incoming edge index (into associated shape array).
uint8_t	index2	Outgoing edge index (into associated shape array).
uint8_t	owner1	Incoming type (either edge on shape A or shape B).
uint8_t	owner2	Outgoing type (either edge on shape A or shape B).

b3LocalManifoldPoint

struct b3LocalManifoldPoint

A local manifold point and normal in frame A.

Collaboration diagram for b3LocalManifoldPoint:

Data Fields
b3FeaturePair	pair	The feature pair for this point.
b3Vec3	point	Local point in frame A.
float	separation	The contact point separation. Negative for overlap.
int	triangleIndex	The triangle index when collide with a mesh or height-field.

b3LocalManifold

struct b3LocalManifold

A local manifold with no dynamic information. Used by b3Collide functions.

Collaboration diagram for b3LocalManifold:

Data Fields
b3TriangleFeature	feature	The triangle feature involved.
int	i1	Vertex 1 index.
int	i2	Vertex 2 index.
int	i3	Vertex 3 index.
b3Vec3	normal	Local normal in frame A.
int	pointCount	The number of manifold points. Only bounded by the buffer capacity.
b3LocalManifoldPoint *	points	The manifold points. From a point buffer.
float	squaredDistance	The squared distance of a sphere from a triangle. For ghost collision reduction.
int	triangleFlags	b3MeshEdgeFlags.
int	triangleIndex	The index of the triangle.
b3Vec3	triangleNormal	The triangle normal.

Enumeration Type Documentation

b3SeparatingFeature

enum b3SeparatingFeature

Cached separating axis feature.

Enumerator
b3_manualFaceAxisA	These are for testing.

b3TriangleFeature

enum b3TriangleFeature

Cached triangle feature.

Enumerator
b3_featureEdge1	v1-v2
b3_featureEdge2	v2-v3
b3_featureEdge3	v3-v1