box2d::Manifold Class Reference

Manifold for two convex shapes. More...

#include <Manifold.hpp>

Classes
struct	Conf
struct	Point
	Point data for a manifold. More...

Public Types
enum	Type : std::uint8_t { e_unset, e_circles, e_faceA, e_faceB }
	Manifold type. More...
using	size_type = std::remove_const< decltype(MaxManifoldPoints)>::type
using	sidx_t = std::remove_const< decltype(MaxShapeVertices)>::type
	Shape index type. More...
using	cf_t = ContactFeature::Type

Public Member Functions
	Manifold ()=default
	Default constructor. More...
	Manifold (const Manifold &copy)=default
constexpr Type	GetType () const noexcept
	Gets the type of this manifold. More...
constexpr size_type	GetPointCount () const noexcept
	Gets the manifold point count. More...
constexpr ContactFeature	GetContactFeature (size_type index) const noexcept
constexpr ContactImpulses	GetContactImpulses (size_type index) const noexcept
void	SetContactImpulses (size_type index, ContactImpulses value) noexcept
const Point &	GetPoint (size_type index) const noexcept
void	SetPointImpulses (size_type index, Momentum n, Momentum t)
void	AddPoint (const Point &mp) noexcept
	Adds a new point. More...
void	AddPoint (cf_t type, sidx_t index, Length2D point) noexcept
constexpr UnitVec2	GetLocalNormal () const noexcept
	Gets the local normal for a face-type manifold. More...
constexpr Length2D	GetLocalPoint () const noexcept
	Gets the local point. More...
constexpr Length2D	GetOpposingPoint (size_type index) const noexcept

Static Public Member Functions
static Manifold	GetForCircles (Length2D vA, sidx_t iA, Length2D vB, sidx_t iB) noexcept
	Gets a circles-typed manifold with one point. More...
static Manifold	GetForFaceA (UnitVec2 normalA, Length2D faceA) noexcept
	Gets a face A typed manifold. More...
static Manifold	GetForFaceA (UnitVec2 ln, Length2D lp, const Point &mp1) noexcept
	Gets a face A typed manifold. More...
static Manifold	GetForFaceA (UnitVec2 ln, Length2D lp, const Point &mp1, const Point &mp2) noexcept
	Gets a face A typed manifold. More...
static Manifold	GetForFaceB (UnitVec2 ln, Length2D lp) noexcept
	Gets a face B typed manifold. More...
static Manifold	GetForFaceB (UnitVec2 ln, Length2D lp, const Point &mp1) noexcept
	Gets a face B typed manifold. More...
static Manifold	GetForFaceB (UnitVec2 ln, Length2D lp, const Point &mp1, const Point &mp2) noexcept
	Gets a face B typed manifold. More...
static Manifold	GetForFaceA (UnitVec2 na, sidx_t ia, Length2D pa) noexcept
static Manifold	GetForFaceB (UnitVec2 nb, sidx_t ib, Length2D pb) noexcept
static Manifold	GetForFaceA (UnitVec2 na, sidx_t ia, Length2D pa, cf_t tb0, sidx_t ib0, Length2D pb0) noexcept
static Manifold	GetForFaceB (UnitVec2 nb, sidx_t ib, Length2D pb, cf_t ta0, sidx_t ia0, Length2D pa0) noexcept
static Manifold	GetForFaceA (UnitVec2 na, sidx_t ia, Length2D pa, cf_t tb0, sidx_t ib0, Length2D pb0, cf_t tb1, sidx_t ib1, Length2D pb1) noexcept
static Manifold	GetForFaceB (UnitVec2 nb, sidx_t ib, Length2D pb, cf_t ta0, sidx_t ia0, Length2D pa0, cf_t ta1, sidx_t ia1, Length2D pa1) noexcept

Detailed Description

Manifold for two convex shapes.

This describes zero, one, or two points of contact for which impulses should be applied to most naturally resolve those contacts. Ideally the manifold is calculated at the earliest point in time of contact occuring. The further past that time, the less natural contact resolution of solid bodies will be - eventually resulting in oddities like tunneling.

Multiple types of contact are supported: clip point versus plane with radius, point versus point with radius (circles). Contacts are stored in this way so that position correction can account for movement, which is critical for continuous physics. All contact scenarios must be expressed in one of these types.

Note

The local point and local normal usage depends on the manifold type. For details, see the documentation associated with the different manifold types.

Every point adds computational overhead to the collision response calculation - so express collision manifolds with one point if possible instead of two.

This data structure is at least 58-bytes large (60-bytes on one 64-bit platform).

See also

Contact.

PositionConstraint.

VelocityConstraint.

Member Typedef Documentation

cf_t

using box2d::Manifold::cf_t = ContactFeature::Type

sidx_t

using box2d::Manifold::sidx_t = std::remove_const<decltype(MaxShapeVertices)>::type

Shape index type.

size_type

using box2d::Manifold::size_type = std::remove_const<decltype(MaxManifoldPoints)>::type

Member Enumeration Documentation

Type

enum box2d::Manifold::Type : std::uint8_t

Manifold type.

Note

This is by design a 1-byte sized type.

Enumerator
e_unset	Unset type. Manifold is unset. For manifolds of this type: the point count is zero, point data is undefined, and all other properties are invalid.
e_circles	Circles type. Manifold is for circle-to-circle like collisions. Note For manifolds of this type: the local point is local center of "circle-A" (where shape A wasn't necessarily a circle but treating it as such is useful), the local normal is invalid (and unused) and, the point count will be zero or one where the contact feature will be ContactFeature{e_vertex, i, e_vertex, j} where i and j are indexes of the vertexes of shapes A and B respectively.
e_faceA	Face-A type. Indicates: local point is center of face A, local normal is normal on shape A, and the local points of Point instances are the local center of cirlce B or a clip point of polygon B where the contact feature will be ContactFeature{e_face, i, e_vertex, j} or ContactFeature{e_face, i, e_face, j} where i and j are indexes for the vertex or edge of shapes A and B respectively..
e_faceB	Face-B type. Indicates: local point is center of face B, local normal is normal on shape B, and the local points of Point instances are the local center of cirlce A or a clip point of polygon A where the contact feature will be ContactFeature{e_face, i, e_vertex, j} or ContactFeature{e_face, i, e_face, j} where i and j are indexes for the vertex or edge of shapes A and B respectively..

Constructor & Destructor Documentation

Manifold() [1/2]

box2d::Manifold::Manifold ( )

default

Default constructor.

Constructs an unset-type manifold. For an unset-type manifold: point count is zero, point data is undefined, and all other properties are invalid.

Manifold() [2/2]

box2d::Manifold::Manifold ( const Manifold &  copy )

default

Member Function Documentation

AddPoint() [1/2]

void box2d::Manifold::AddPoint ( const Point &  mp )

inlinenoexcept

Adds a new point.

This can be called once for circle type manifolds, and up to twice for face-A or face-B type manifolds. GetPointCount() can be called to find out how many points have already been added.

Note

Behavior is undefined if this object's type is e_unset.

Behavior is undefined if this is called more than twice.

AddPoint() [2/2]

void box2d::Manifold::AddPoint ( cf_t  type, sidx_t  index, Length2D  point  )

inlinenoexcept

GetContactFeature()

constexpr ContactFeature box2d::Manifold::GetContactFeature ( size_type  index ) const

inlinenoexcept

GetContactImpulses()

constexpr ContactImpulses box2d::Manifold::GetContactImpulses ( size_type  index ) const

inlinenoexcept

GetForCircles()

static Manifold box2d::Manifold::GetForCircles ( Length2D  vA, sidx_t  iA, Length2D  vB, sidx_t  iB  )

inlinestaticnoexcept

Gets a circles-typed manifold with one point.

Parameters

vA	Local center of "circle" A.
iA	Index of vertex from shape A representing the local center of "circle" A.
vB	Local center of "circle" B.
iB	Index of vertex from shape B representing the local center of "circle" B.

GetForFaceA() [1/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  normalA, Length2D  faceA  )

inlinestaticnoexcept

Gets a face A typed manifold.

Parameters

normalA	Local normal of the face from polygon A.
faceA	Any point in local coordinates on the face whose normal was provided.

GetForFaceA() [2/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  ln, Length2D  lp, const Point &  mp1  )

inlinestaticnoexcept

Gets a face A typed manifold.

Parameters

ln	Normal on polygon A.
lp	Center of face A.
mp1	Manifold point 1 (of 1).

GetForFaceA() [3/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  ln, Length2D  lp, const Point &  mp1, const Point &  mp2  )

inlinestaticnoexcept

Gets a face A typed manifold.

Parameters

ln	Normal on polygon A.
lp	Center of face A.
mp1	Manifold point 1 (of 2).
mp2	Manifold point 2 (of 2).

GetForFaceA() [4/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  na, sidx_t  ia, Length2D  pa  )

inlinestaticnoexcept

GetForFaceA() [5/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  na, sidx_t  ia, Length2D  pa, cf_t  tb0, sidx_t  ib0, Length2D  pb0  )

inlinestaticnoexcept

GetForFaceA() [6/6]

static Manifold box2d::Manifold::GetForFaceA ( UnitVec2  na, sidx_t  ia, Length2D  pa, cf_t  tb0, sidx_t  ib0, Length2D  pb0, cf_t  tb1, sidx_t  ib1, Length2D  pb1  )

inlinestaticnoexcept

GetForFaceB() [1/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  ln, Length2D  lp  )

inlinestaticnoexcept

Gets a face B typed manifold.

Parameters

ln	Normal on polygon B.
lp	Center of face B.

GetForFaceB() [2/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  ln, Length2D  lp, const Point &  mp1  )

inlinestaticnoexcept

Gets a face B typed manifold.

Parameters

ln	Normal on polygon B.
lp	Center of face B.
mp1	Manifold point 1.

GetForFaceB() [3/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  ln, Length2D  lp, const Point &  mp1, const Point &  mp2  )

inlinestaticnoexcept

Gets a face B typed manifold.

Parameters

ln	Normal on polygon B.
lp	Center of face B.
mp1	Manifold point 1 (of 2).
mp2	Manifold point 2 (of 2).

GetForFaceB() [4/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  nb, sidx_t  ib, Length2D  pb  )

inlinestaticnoexcept

GetForFaceB() [5/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  nb, sidx_t  ib, Length2D  pb, cf_t  ta0, sidx_t  ia0, Length2D  pa0  )

inlinestaticnoexcept

GetForFaceB() [6/6]

static Manifold box2d::Manifold::GetForFaceB ( UnitVec2  nb, sidx_t  ib, Length2D  pb, cf_t  ta0, sidx_t  ia0, Length2D  pa0, cf_t  ta1, sidx_t  ia1, Length2D  pa1  )

inlinestaticnoexcept

GetLocalNormal()

constexpr UnitVec2 box2d::Manifold::GetLocalNormal ( ) const

inlinenoexcept

Gets the local normal for a face-type manifold.

Returns

Local normal if the manifold type is face A or face B, else invalid value.

GetLocalPoint()

constexpr Length2D box2d::Manifold::GetLocalPoint ( ) const

inlinenoexcept

Gets the local point.

This is the: local center of "circle" A for circles-type manifolds, the center of face A for face-A-type manifolds, and the center of face B for face-B-type manifolds.

Note

Value invalid for unset (e_unset) type manifolds.

Returns

Local point.

GetOpposingPoint()

constexpr Length2D box2d::Manifold::GetOpposingPoint ( size_type  index ) const

inlinenoexcept

GetPoint()

const Point& box2d::Manifold::GetPoint ( size_type  index ) const

inlinenoexcept

GetPointCount()

constexpr size_type box2d::Manifold::GetPointCount ( ) const

inlinenoexcept

Gets the manifold point count.

This is the count of contact points for this manifold. Only up to this many points can be validly accessed using the GetPoint() method.

Note

Non-zero values indicate that the two shapes are touching.

Returns

Value between 0 and MaxManifoldPoints.

See also

MaxManifoldPoints.

AddPoint().

GetPoint().

GetType()

constexpr Type box2d::Manifold::GetType ( ) const

inlinenoexcept

Gets the type of this manifold.

Note

This must be a constant expression in order to use it in the context of the IsValid specialized template function for it.

SetContactImpulses()

void box2d::Manifold::SetContactImpulses ( size_type  index, ContactImpulses  value  )

inlinenoexcept

SetPointImpulses()

void box2d::Manifold::SetPointImpulses ( size_type  index, Momentum  n, Momentum  t  )

inline

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The documentation for this class was generated from the following file:

• Manifold.hpp