Solver to compute contact patches, i.e. the intersection between two contact surfaces projected onto the shapes' separating plane. Otherwise said, a contact patch is simply the intersection between two support sets: the support set of shape S1 in direction n and the support set of shape S2 in direction -n, where n is the contact normal (satisfying the optimality conditions of GJK/EPA). More...

#include <coal/contact_patch/contact_patch_solver.h>

Collaboration diagram for coal::ContactPatchSolver:

[legend]

Public Types
using	ShapeSupportData = details::ShapeSupportData

using	SupportSetDirection = SupportSet::PatchDirection

typedef void(*	SupportSetFunction) (const ShapeBase *shape, SupportSet &support_set, int &hint, ShapeSupportData &support_data, size_t num_sampled_supports, Scalar tol)
	Support set function for shape si. More...

Public Member Functions
	ContactPatchSolver ()
	Default constructor. More...

	ContactPatchSolver (const ContactPatchRequest &request)
	Construct the solver with a `ContactPatchRequest`. More...

void	set (const ContactPatchRequest &request)
	Set up the solver using a `ContactPatchRequest`. More...

void	setSupportGuess (const support_func_guess_t guess) const
	Sets the support guess used during support set computation of shapes s1 and s2. More...

template<typename ShapeType1 , typename ShapeType2 >
void	computePatch (const ShapeType1 &s1, const Transform3s &tf1, const ShapeType2 &s2, const Transform3s &tf2, const Contact &contact, ContactPatch &contact_patch) const
	Main API of the solver: compute a contact patch from a contact between shapes s1 and s2. The contact patch is the (triple) intersection between the separating plane passing (by `contact.pos` and supported by `contact.normal`) and the shapes s1 and s2. More...

template<typename ShapeType1 , typename ShapeType2 >
void	reset (const ShapeType1 &shape1, const Transform3s &tf1, const ShapeType2 &shape2, const Transform3s &tf2, const ContactPatch &contact_patch) const
	Reset the internal quantities of the solver. More...

void	getResult (const Contact &contact, const ContactPatch::Polygon *result, ContactPatch &contact_patch) const
	Retrieve result, adds a post-processing step if result has bigger size than `this->max_patch_size`. More...

bool	operator== (const ContactPatchSolver &other) const

Static Public Member Functions
static Vec2s	computeLineSegmentIntersection (const Vec2s &a, const Vec2s &b, const Vec2s &c, const Vec2s &d)

static SupportSetFunction	makeSupportSetFunction (const ShapeBase *shape, ShapeSupportData &support_data)
	Construct support set function for shape. More...

Public Attributes
size_t	num_samples_curved_shapes
	Number of points sampled for Cone and Cylinder when the normal is orthogonal to the shapes' basis. See ContactPatchRequest::m_num_samples_curved_shapes for more details. More...

Scalar	patch_tolerance
	Tolerance below which points are added to the shapes support sets. See ContactPatchRequest::m_patch_tolerance for more details. More...

SupportSetFunction	supportFuncShape1
	Support set function for shape s1. More...

SupportSetFunction	supportFuncShape2
	Support set function for shape s2. More...

std::array< ShapeSupportData, 2 >	supports_data
	Temporary data to compute the support sets on each shape. More...

support_func_guess_t	support_guess
	Guess for the support sets computation. More...

SupportSet	support_set_shape1
	Holder for support set of shape 1, used for internal computation. After `computePatch` has been called, this support set is no longer valid. More...

SupportSet	support_set_shape2
	Holder for support set of shape 2, used for internal computation. After `computePatch` has been called, this support set is no longer valid. More...

SupportSet	support_set_buffer
	Temporary support set used for the Sutherland-Hodgman algorithm. More...

std::vector< bool >	added_to_patch
	Tracks which point of the Sutherland-Hodgman result have been added to the contact patch. Only used if the post-processing step occurs, i.e. if the result of Sutherland-Hodgman has a size bigger than `max_patch_size`. More...

Static Public Attributes
static constexpr size_t	default_num_preallocated_supports = 16
	Number of vectors to pre-allocate in the `m_clipping_sets` vectors. More...

Detailed Description

Solver to compute contact patches, i.e. the intersection between two contact surfaces projected onto the shapes' separating plane. Otherwise said, a contact patch is simply the intersection between two support sets: the support set of shape S1 in direction n and the support set of shape S2 in direction -n, where n is the contact normal (satisfying the optimality conditions of GJK/EPA).

Note: A contact patch is not the support set of the Minkowski Difference in the direction of the normal. A contact patch is actually the support set of the Minkowski difference in the direction of the normal, i.e. the instersection of the shapes support sets as mentioned above.

TODO(louis): algo improvement:

The clipping algo is currently n1 * n2; it can be done in n1 + n2.

Member Typedef Documentation

◆ ShapeSupportData

using coal::ContactPatchSolver::ShapeSupportData = details::ShapeSupportData

◆ SupportSetDirection

using coal::ContactPatchSolver::SupportSetDirection = SupportSet::PatchDirection

◆ SupportSetFunction

typedef void(* coal::ContactPatchSolver::SupportSetFunction) (const ShapeBase *shape, SupportSet &support_set, int &hint, ShapeSupportData &support_data, size_t num_sampled_supports, Scalar tol)

Support set function for shape si.

Parameters

[in]	shape	the shape.
	[in/out]	support_set a support set of the shape. A support set is attached to a frame. All the points of the set computed by this function will be expressed in the local frame of the support set. The support set is computed in the direction of the positive z-axis if its direction is DEFAULT, negative z-axis if its direction is INVERTED.
	[in/out]	hint for the support computation of ConvexBase shapes. Gets updated after calling the function onto ConvexBase shapes.
	[in/out]	support_data for the support computation of ConvexBase shapes. Gets updated with visited vertices after calling the function onto ConvexBase shapes.
[in]	num_sampled_supports	for shapes like cone or cylinders which have smooth non-strictly convex sides (their bases are circles), we need to know how many supports we sample from these sides. For any other shape, this parameter is not used.
[in]	tol	the "thickness" of the support plane. Any point v which satisfies `max_{x in shape}(x.dot(dir)) - v.dot(dir) <= tol` is tol distant from the support plane and is added to the support set.

Constructor & Destructor Documentation

◆ ContactPatchSolver() [1/2]

coal::ContactPatchSolver::ContactPatchSolver ( )

inlineexplicit

Default constructor.

◆ ContactPatchSolver() [2/2]

coal::ContactPatchSolver::ContactPatchSolver ( const ContactPatchRequest & request )

inlineexplicit

Construct the solver with a ContactPatchRequest.

Member Function Documentation

◆ computeLineSegmentIntersection()

Vec2s coal::ContactPatchSolver::computeLineSegmentIntersection	(	const Vec2s &	a,
		const Vec2s &	b,
		const Vec2s &	c,
		const Vec2s &	d
	)

inlinestatic

Returns: the intersecting point between line defined by ray (a, b) and the segment [c, d].

Note: we make the following hypothesis: 1) c != d (should be when creating initial polytopes) 2) (c, d) is not parallel to ray -> if so, we return d.

◆ computePatch()

template<typename ShapeType1 , typename ShapeType2 >

void coal::ContactPatchSolver::computePatch	(	const ShapeType1 &	s1,
		const Transform3s &	tf1,
		const ShapeType2 &	s2,
		const Transform3s &	tf2,
		const Contact &	contact,
		ContactPatch &	contact_patch
	)		const

Main API of the solver: compute a contact patch from a contact between shapes s1 and s2. The contact patch is the (triple) intersection between the separating plane passing (by contact.pos and supported by contact.normal) and the shapes s1 and s2.

◆ getResult()

void coal::ContactPatchSolver::getResult	(	const Contact &	contact,
		const ContactPatch::Polygon *	result,
		ContactPatch &	contact_patch
	)		const

inline

Retrieve result, adds a post-processing step if result has bigger size than this->max_patch_size.

◆ makeSupportSetFunction()

static SupportSetFunction coal::ContactPatchSolver::makeSupportSetFunction	(	const ShapeBase *	shape,
		ShapeSupportData &	support_data
	)

static

Construct support set function for shape.

◆ operator==()

bool coal::ContactPatchSolver::operator== ( const ContactPatchSolver & other ) const

inline

◆ reset()

template<typename ShapeType1 , typename ShapeType2 >

void coal::ContactPatchSolver::reset	(	const ShapeType1 &	shape1,
		const Transform3s &	tf1,
		const ShapeType2 &	shape2,
		const Transform3s &	tf2,
		const ContactPatch &	contact_patch
	)		const

inline

Reset the internal quantities of the solver.

◆ set()

void coal::ContactPatchSolver::set ( const ContactPatchRequest & request )

inline

Set up the solver using a ContactPatchRequest.

◆ setSupportGuess()

void coal::ContactPatchSolver::setSupportGuess ( const support_func_guess_t guess ) const

inline

Sets the support guess used during support set computation of shapes s1 and s2.

Member Data Documentation

◆ added_to_patch

std::vector<bool> coal::ContactPatchSolver::added_to_patch

mutable

Tracks which point of the Sutherland-Hodgman result have been added to the contact patch. Only used if the post-processing step occurs, i.e. if the result of Sutherland-Hodgman has a size bigger than max_patch_size.

◆ default_num_preallocated_supports

constexpr size_t coal::ContactPatchSolver::default_num_preallocated_supports = 16

staticconstexpr

Number of vectors to pre-allocate in the m_clipping_sets vectors.

◆ num_samples_curved_shapes

size_t coal::ContactPatchSolver::num_samples_curved_shapes

Number of points sampled for Cone and Cylinder when the normal is orthogonal to the shapes' basis. See ContactPatchRequest::m_num_samples_curved_shapes for more details.

◆ patch_tolerance

Scalar coal::ContactPatchSolver::patch_tolerance

Tolerance below which points are added to the shapes support sets. See ContactPatchRequest::m_patch_tolerance for more details.

◆ support_guess

support_func_guess_t coal::ContactPatchSolver::support_guess

mutable

Guess for the support sets computation.

◆ support_set_buffer

SupportSet coal::ContactPatchSolver::support_set_buffer

mutable

Temporary support set used for the Sutherland-Hodgman algorithm.

◆ support_set_shape1

SupportSet coal::ContactPatchSolver::support_set_shape1

mutable

Holder for support set of shape 1, used for internal computation. After computePatch has been called, this support set is no longer valid.

◆ support_set_shape2

SupportSet coal::ContactPatchSolver::support_set_shape2

mutable

Holder for support set of shape 2, used for internal computation. After computePatch has been called, this support set is no longer valid.

◆ supportFuncShape1

SupportSetFunction coal::ContactPatchSolver::supportFuncShape1

mutable

Support set function for shape s1.

◆ supportFuncShape2

SupportSetFunction coal::ContactPatchSolver::supportFuncShape2

mutable

Support set function for shape s2.

◆ supports_data

std::array<ShapeSupportData, 2> coal::ContactPatchSolver::supports_data

mutable

Temporary data to compute the support sets on each shape.

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

include/coal/contact_patch/contact_patch_solver.h
include/coal/contact_patch/contact_patch_solver.hxx

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Detailed Description

Member Typedef Documentation

◆ ShapeSupportData

◆ SupportSetDirection

◆ SupportSetFunction

Constructor & Destructor Documentation

◆ ContactPatchSolver() [1/2]

◆ ContactPatchSolver() [2/2]

Member Function Documentation

◆ computeLineSegmentIntersection()

◆ computePatch()

◆ getResult()

◆ makeSupportSetFunction()

◆ operator==()

◆ reset()

◆ set()

◆ setSupportGuess()

Member Data Documentation

◆ added_to_patch

◆ default_num_preallocated_supports

◆ num_samples_curved_shapes

◆ patch_tolerance

◆ support_guess

◆ support_set_buffer

◆ support_set_shape1

◆ support_set_shape2

◆ supportFuncShape1

◆ supportFuncShape2

◆ supports_data