Bullet Collision Detection & Physics Library
btContactConstraint.cpp
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1 /*
2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2003-2006 Erwin Coumans http://continuousphysics.com/Bullet/
4 
5 This software is provided 'as-is', without any express or implied warranty.
6 In no event will the authors be held liable for any damages arising from the use of this software.
7 Permission is granted to anyone to use this software for any purpose,
8 including commercial applications, and to alter it and redistribute it freely,
9 subject to the following restrictions:
10 
11 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
12 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
13 3. This notice may not be removed or altered from any source distribution.
14 */
15 
16 #include "btContactConstraint.h"
18 #include "LinearMath/btVector3.h"
19 #include "btJacobianEntry.h"
20 #include "btContactSolverInfo.h"
21 #include "LinearMath/btMinMax.h"
23 
26  m_contactManifold(*contactManifold)
27 {
28 }
29 
31 {
32 }
33 
35 {
36  m_contactManifold = *contactManifold;
37 }
38 
40 {
41 }
42 
44 {
45 }
46 
48 {
49 }
50 
51 #include "btContactConstraint.h"
53 #include "LinearMath/btVector3.h"
54 #include "btJacobianEntry.h"
55 #include "btContactSolverInfo.h"
56 #include "LinearMath/btMinMax.h"
58 
59 //response between two dynamic objects without friction and no restitution, assuming 0 penetration depth
61  btRigidBody* body1,
62  btCollisionObject* colObj2,
63  const btVector3& contactPositionWorld,
64  const btVector3& contactNormalOnB,
65  const btContactSolverInfo& solverInfo,
66  btScalar distance)
67 {
68  btRigidBody* body2 = btRigidBody::upcast(colObj2);
69 
70  const btVector3& normal = contactNormalOnB;
71 
72  btVector3 rel_pos1 = contactPositionWorld - body1->getWorldTransform().getOrigin();
73  btVector3 rel_pos2 = contactPositionWorld - colObj2->getWorldTransform().getOrigin();
74 
75  btVector3 vel1 = body1->getVelocityInLocalPoint(rel_pos1);
76  btVector3 vel2 = body2 ? body2->getVelocityInLocalPoint(rel_pos2) : btVector3(0, 0, 0);
77  btVector3 vel = vel1 - vel2;
78  btScalar rel_vel;
79  rel_vel = normal.dot(vel);
80 
81  btScalar combinedRestitution = 0.f;
82  btScalar restitution = combinedRestitution * -rel_vel;
83 
84  btScalar positionalError = solverInfo.m_erp * -distance / solverInfo.m_timeStep;
85  btScalar velocityError = -(1.0f + restitution) * rel_vel; // * damping;
86  btScalar denom0 = body1->computeImpulseDenominator(contactPositionWorld, normal);
87  btScalar denom1 = body2 ? body2->computeImpulseDenominator(contactPositionWorld, normal) : 0.f;
88  btScalar relaxation = 1.f;
89  btScalar jacDiagABInv = relaxation / (denom0 + denom1);
90 
91  btScalar penetrationImpulse = positionalError * jacDiagABInv;
92  btScalar velocityImpulse = velocityError * jacDiagABInv;
93 
94  btScalar normalImpulse = penetrationImpulse + velocityImpulse;
95  normalImpulse = 0.f > normalImpulse ? 0.f : normalImpulse;
96 
97  body1->applyImpulse(normal * (normalImpulse), rel_pos1);
98  if (body2)
99  body2->applyImpulse(-normal * (normalImpulse), rel_pos2);
100 
101  return normalImpulse;
102 }
103 
104 //bilateral constraint between two dynamic objects
106  btRigidBody& body2, const btVector3& pos2,
107  btScalar distance, const btVector3& normal, btScalar& impulse, btScalar timeStep)
108 {
109  (void)timeStep;
110  (void)distance;
111 
112  btScalar normalLenSqr = normal.length2();
113  btAssert(btFabs(normalLenSqr) < btScalar(1.1));
114  if (normalLenSqr > btScalar(1.1))
115  {
116  impulse = btScalar(0.);
117  return;
118  }
119  btVector3 rel_pos1 = pos1 - body1.getCenterOfMassPosition();
120  btVector3 rel_pos2 = pos2 - body2.getCenterOfMassPosition();
121  //this jacobian entry could be re-used for all iterations
122 
123  btVector3 vel1 = body1.getVelocityInLocalPoint(rel_pos1);
124  btVector3 vel2 = body2.getVelocityInLocalPoint(rel_pos2);
125  btVector3 vel = vel1 - vel2;
126 
129  rel_pos1, rel_pos2, normal, body1.getInvInertiaDiagLocal(), body1.getInvMass(),
130  body2.getInvInertiaDiagLocal(), body2.getInvMass());
131 
132  btScalar jacDiagAB = jac.getDiagonal();
133  btScalar jacDiagABInv = btScalar(1.) / jacDiagAB;
134 
135  btScalar rel_vel = jac.getRelativeVelocity(
136  body1.getLinearVelocity(),
138  body2.getLinearVelocity(),
140 
141  rel_vel = normal.dot(vel);
142 
143  //todo: move this into proper structure
144  btScalar contactDamping = btScalar(0.2);
145 
146 #ifdef ONLY_USE_LINEAR_MASS
147  btScalar massTerm = btScalar(1.) / (body1.getInvMass() + body2.getInvMass());
148  impulse = -contactDamping * rel_vel * massTerm;
149 #else
150  btScalar velocityImpulse = -contactDamping * rel_vel * jacDiagABInv;
151  impulse = velocityImpulse;
152 #endif
153 }
static const btRigidBody * upcast(const btCollisionObject *colObj)
to keep collision detection and dynamics separate we don&#39;t store a rigidbody pointer but a rigidbody ...
Definition: btRigidBody.h:189
virtual void buildJacobian()
obsolete methods
btPersistentManifold is a contact point cache, it stays persistent as long as objects are overlapping...
btScalar computeImpulseDenominator(const btVector3 &pos, const btVector3 &normal) const
Definition: btRigidBody.h:390
const btVector3 & getAngularVelocity() const
Definition: btRigidBody.h:357
Jacobian entry is an abstraction that allows to describe constraints it can be used in combination wi...
const btTransform & getCenterOfMassTransform() const
Definition: btRigidBody.h:349
btScalar length2() const
Return the length of the vector squared.
Definition: btVector3.h:251
virtual void getInfo2(btConstraintInfo2 *info)
internal method used by the constraint solver, don&#39;t use them directly
#define btAssert(x)
Definition: btScalar.h:133
btContactConstraint(btPersistentManifold *contactManifold, btRigidBody &rbA, btRigidBody &rbB)
btMatrix3x3 transpose() const
Return the transpose of the matrix.
Definition: btMatrix3x3.h:1026
virtual void getInfo1(btConstraintInfo1 *info)
internal method used by the constraint solver, don&#39;t use them directly
btTransform & getWorldTransform()
const btVector3 & getInvInertiaDiagLocal() const
Definition: btRigidBody.h:286
btVector3 & getOrigin()
Return the origin vector translation.
Definition: btTransform.h:113
const btVector3 & getLinearVelocity() const
Definition: btRigidBody.h:353
void resolveSingleBilateral(btRigidBody &body1, const btVector3 &pos1, btRigidBody &body2, const btVector3 &pos2, btScalar distance, const btVector3 &normal, btScalar &impulse, btScalar timeStep)
resolveSingleBilateral is an obsolete methods used for vehicle friction between two dynamic objects ...
btScalar getInvMass() const
Definition: btRigidBody.h:261
btScalar dot(const btVector3 &v) const
Return the dot product.
Definition: btVector3.h:229
btCollisionObject can be used to manage collision detection objects.
btMatrix3x3 & getBasis()
Return the basis matrix for the rotation.
Definition: btTransform.h:108
The btRigidBody is the main class for rigid body objects.
Definition: btRigidBody.h:59
void setContactManifold(btPersistentManifold *contactManifold)
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:80
btVector3 getVelocityInLocalPoint(const btVector3 &rel_pos) const
Definition: btRigidBody.h:374
const btVector3 & getCenterOfMassPosition() const
Definition: btRigidBody.h:343
btScalar getDiagonal() const
TypedConstraint is the baseclass for Bullet constraints and vehicles.
btScalar resolveSingleCollision(btRigidBody *body1, btCollisionObject *colObj2, const btVector3 &contactPositionWorld, const btVector3 &contactNormalOnB, const btContactSolverInfo &solverInfo, btScalar distance)
void applyImpulse(const btVector3 &impulse, const btVector3 &rel_pos)
Definition: btRigidBody.h:323
btPersistentManifold m_contactManifold
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:294
btScalar btFabs(btScalar x)
Definition: btScalar.h:477