A collision response oriented description of the intersection of two convex shapes. More...

#include <playrho/d2/Manifold.hpp>

Classes
struct	Conf
	Configuration data for manifold calculation. More...

struct	Point
	Data for a point of collision in a Manifold. More...

Public Types
using	CfIndex = ContactFeature::Index
	The contact feature index.

using	size_type = std::remove_const_t< decltype(MaxManifoldPoints)>
	Size type.

enum	Type : std::uint8_t { e_unset , e_circles , e_faceA , e_faceB }
	Manifold type. More...

Public Member Functions
	Manifold ()=default

void	AddPoint (const Point &mp) noexcept

constexpr ContactFeature	GetContactFeature (size_type index) const noexcept
	Gets the contact feature for the given index. More...

constexpr Momentum2	GetImpulses (size_type index) const noexcept
	Gets the impulses for the given index. More...

constexpr UnitVec	GetLocalNormal () const noexcept
	Gets the local normal for a face-type manifold. More...

constexpr Length2	GetLocalPoint () const noexcept
	Gets the local point. More...

constexpr Length2	GetOpposingPoint (size_type index) const noexcept
	Gets the opposing point. More...

const Point &	GetPoint (size_type index) const noexcept
	Gets the point identified by the given index. More...

constexpr size_type	GetPointCount () const noexcept

constexpr Type	GetType () const noexcept

void	SetImpulses (size_type index, const Momentum2 &value) noexcept
	Sets the impulses for the given index. More...

void	SetImpulses (size_type index, Momentum n, Momentum t) noexcept
	Sets the impulses for the given index. More...

Static Public Member Functions
static Manifold	GetForCircles (const Length2 &vA, CfIndex iA, const Length2 &vB, CfIndex iB) noexcept

static Manifold	GetForFaceA (const UnitVec &ln, const Length2 &lp, const Point &mp1) noexcept

static Manifold	GetForFaceA (const UnitVec &ln, const Length2 &lp, const Point &mp1, const Point &mp2) noexcept

static Manifold	GetForFaceA (const UnitVec &normalA, const Length2 &faceA) noexcept

static Manifold	GetForFaceB (const UnitVec &ln, const Length2 &lp) noexcept

static Manifold	GetForFaceB (const UnitVec &ln, const Length2 &lp, const Point &mp1) noexcept

static Manifold	GetForFaceB (const UnitVec &ln, const Length2 &lp, const Point &mp1, const Point &mp2) noexcept

Related Functions
(Note that these are not member functions.)
Manifold	CollideShapes (const DistanceProxy &shapeA, const Transformation &xfA, const DistanceProxy &shapeB, const Transformation &xfB, const Manifold::Conf &conf=GetDefaultManifoldConf())
	Calculates the relevant collision manifold. More...

WorldManifold	GetWorldManifold (const Manifold &manifold, const Transformation &xfA, Length radiusA, const Transformation &xfB, Length radiusB)
	Gets the world manifold for the given data. More...

constexpr auto	IsValid (const d2::Manifold &value) noexcept -> bool
	Gets whether the given manifold is valid.

bool	operator!= (const Manifold &lhs, const Manifold &rhs) noexcept
	Manifold inequality operator. More...

bool	operator== (const Manifold &lhs, const Manifold &rhs) noexcept
	Manifold equality operator. More...

Detailed Description

A collision response oriented description of the intersection of 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 occurring. 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.

Conceptually, a manifold represents the intersection of two convex sets (which is itself a convex set) and a solution for moving the sets away from each other to eliminate the intersection.

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.

See also: Contact, PositionConstraint, VelocityConstraint; https://en.wikipedia.org/wiki/Convex_set; http://box2d.org/files/GDC2007/GDC2007_Catto_Erin_Physics2.ppt

Member Enumeration Documentation

◆ Type

enum playrho::d2::Manifold::Type : std::uint8_t

Manifold type.

Enumerator
e_unset	Unset type. Manifold is unset. For manifolds of this type: the point count is zero, point data is not defined, 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 circle 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 circle 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()

playrho::d2::Manifold::Manifold ( )

default

Default constructor.

Constructs an unset-type manifold. For an unset-type manifold: point count is zero, point data is not defined, and all other properties are invalid.

Member Function Documentation

◆ AddPoint()

void playrho::d2::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.

Precondition: GetType() is not e_unset.; GetPointCount() is less than MaxManifoldPoints.

◆ GetContactFeature()

constexpr ContactFeature playrho::d2::Manifold::GetContactFeature ( size_type index ) const

inlineconstexprnoexcept

Gets the contact feature for the given index.

Precondition: index is less than GetPointCount().

◆ GetForCircles()

static Manifold playrho::d2::Manifold::GetForCircles	(	const Length2 &	vA,
		CfIndex	iA,
		const Length2 &	vB,
		CfIndex	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.

Referenced by playrho::d2::GetManifold().

◆ GetForFaceA() [1/3]

static Manifold playrho::d2::Manifold::GetForFaceA	(	const UnitVec &	ln,
		const Length2 &	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() [2/3]

static Manifold playrho::d2::Manifold::GetForFaceA	(	const UnitVec &	ln,
		const Length2 &	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() [3/3]

static Manifold playrho::d2::Manifold::GetForFaceA	(	const UnitVec &	normalA,
		const Length2 &	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.

Referenced by playrho::d2::GetManifold().

◆ GetForFaceB() [1/3]

static Manifold playrho::d2::Manifold::GetForFaceB	(	const UnitVec &	ln,
		const Length2 &	lp
	)

inlinestaticnoexcept

Gets a face B typed manifold.

Parameters

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

Referenced by playrho::d2::GetManifold().

◆ GetForFaceB() [2/3]

static Manifold playrho::d2::Manifold::GetForFaceB	(	const UnitVec &	ln,
		const Length2 &	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() [3/3]

static Manifold playrho::d2::Manifold::GetForFaceB	(	const UnitVec &	ln,
		const Length2 &	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).

◆ GetImpulses()

constexpr Momentum2 playrho::d2::Manifold::GetImpulses ( size_type index ) const

inlineconstexprnoexcept

Gets the impulses for the given index.

Precondition: index is less than GetPointCount().

Returns: Pair of impulses where the first impulse is the "normal impulse" and the second impulse is the "tangent impulse".

◆ GetLocalNormal()

constexpr UnitVec playrho::d2::Manifold::GetLocalNormal ( ) const

inlineconstexprnoexcept

Gets the local normal for a face-type manifold.

Note: Only valid for face-A or face-B type manifolds.

Precondition: This is a face manifold, i.e.: GetType() == e_faceA || GetType() == e_faceB.

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

Referenced by playrho::d2::GetPSM().

◆ GetLocalPoint()

constexpr Length2 playrho::d2::Manifold::GetLocalPoint ( ) const

inlineconstexprnoexcept

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; or the center of face B for face-B-type manifolds.

Note: Only valid for circle, face-A, or face-B type manifolds.

Precondition: This is not an unset manifold, i.e. GetType() != e_unset.

Returns: Local point.

Referenced by playrho::d2::GetPSM().

◆ GetOpposingPoint()

constexpr Length2 playrho::d2::Manifold::GetOpposingPoint ( size_type index ) const

inlineconstexprnoexcept

Gets the opposing point.

Precondition: index is less than GetPointCount().

◆ GetPoint()

const Point& playrho::d2::Manifold::GetPoint ( size_type index ) const

inlinenoexcept

Gets the point identified by the given index.

Precondition: index is less than GetPointCount().

Referenced by playrho::d2::GetPSM().

◆ GetPointCount()

constexpr size_type playrho::d2::Manifold::GetPointCount ( ) const

inlineconstexprnoexcept

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() function.

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

Returns: Value between 0 and MaxManifoldPoints.

See also: MaxManifoldPoints, AddPoint(), GetPoint().

Referenced by GetContactFeature(), GetImpulses(), GetOpposingPoint(), GetPoint(), SetImpulses(), and playrho::GaussSeidel::SolvePositionConstraint().

◆ GetType()

constexpr Type playrho::d2::Manifold::GetType ( ) const

inlineconstexprnoexcept

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.

Referenced by GetLocalNormal(), GetLocalPoint(), playrho::d2::GetPSM(), and GetWorldManifold().

◆ SetImpulses() [1/2]

void playrho::d2::Manifold::SetImpulses	(	size_type	index,
		const Momentum2 &	value
	)

inlinenoexcept

Sets the impulses for the given index.

Sets the contact impulses for the given index where the first impulse is the "normal impulse" and the second impulse is the "tangent impulse".

Precondition: index is less than GetPointCount().

◆ SetImpulses() [2/2]

void playrho::d2::Manifold::SetImpulses	(	size_type	index,
		Momentum	n,
		Momentum	t
	)

inlinenoexcept

Sets the impulses for the given index.

Precondition: index is less than GetPointCount().

Friends And Related Function Documentation

◆ CollideShapes()

Manifold CollideShapes	(	const DistanceProxy &	shapeA,
		const Transformation &	xfA,
		const DistanceProxy &	shapeB,
		const Transformation &	xfB,
		const Manifold::Conf &	conf = `GetDefaultManifoldConf()`
	)

Note: The returned touching state information typically agrees with that returned from the distance-proxy-based TestOverlap function. This is not always the case however especially when the separation or overlap distance is closer to zero.

◆ GetWorldManifold()

WorldManifold GetWorldManifold	(	const Manifold &	manifold,
		const Transformation &	xfA,
		Length	radiusA,
		const Transformation &	xfB,
		Length	radiusB
	)

Precondition: The given manifold input has between 0 and 2 points.

Parameters

manifold	Manifold to use. Uses the manifold's type, local point, local normal, point-count, and the indexed-points' local point data.
xfA	Transformation A.
radiusA	Radius of shape A.
xfB	Transformation B.
radiusB	Radius of shape B.

Returns: World manifold value for the given inputs which will have the same number of points as the given manifold has. The returned world manifold points will be the mid-points of the manifold intersection.

◆ operator!=()

bool operator!=	(	const Manifold &	lhs,
		const Manifold &	rhs
	)

Determines whether the two given manifolds are not equal.

◆ operator==()

bool operator==	(	const Manifold &	lhs,
		const Manifold &	rhs
	)

Note: In-so-far as manifold points are concerned, order doesn't matter; only whether the two manifolds have the same point set.

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

Library/include/playrho/d2/Manifold.hpp
Library/include/playrho/d2/WorldManifold.hpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Related Functions

Detailed Description

Member Enumeration Documentation

◆ Type

Constructor & Destructor Documentation

◆ Manifold()

Member Function Documentation

◆ AddPoint()

◆ GetContactFeature()

◆ GetForCircles()

◆ GetForFaceA() [1/3]

◆ GetForFaceA() [2/3]

◆ GetForFaceA() [3/3]

◆ GetForFaceB() [1/3]

◆ GetForFaceB() [2/3]

◆ GetForFaceB() [3/3]

◆ GetImpulses()

◆ GetLocalNormal()

◆ GetLocalPoint()

◆ GetOpposingPoint()

◆ GetPoint()

◆ GetPointCount()

◆ GetType()

◆ SetImpulses() [1/2]

◆ SetImpulses() [2/2]

Friends And Related Function Documentation

◆ CollideShapes()

◆ GetWorldManifold()

◆ operator!=()

◆ operator==()