Bullet Collision Detection & Physics Library: btDeformableBodySolver.h Source File

Bullet Collision Detection & Physics Library

btDeformableBodySolver.h
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1 /*
2 Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
3
4 Bullet Continuous Collision Detection and Physics Library
5 Copyright (c) 2019 Google Inc. http://bulletphysics.org
6 This software is provided 'as-is', without any express or implied warranty.
7 In no event will the authors be held liable for any damages arising from the use of this software.
8 Permission is granted to anyone to use this software for any purpose,
9 including commercial applications, and to alter it and redistribute it freely,
10 subject to the following restrictions:
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 #ifndef BT_DEFORMABLE_BODY_SOLVERS_H
17 #define BT_DEFORMABLE_BODY_SOLVERS_H
18
19 #include "btSoftBodySolvers.h"
20 #include "btDeformableBackwardEulerObjective.h"
21 #include "btDeformableMultiBodyDynamicsWorld.h"
22 #include "BulletDynamics/Featherstone/btMultiBodyLinkCollider.h"
23 #include "BulletDynamics/Featherstone/btMultiBodyConstraint.h"
24 #include "btConjugateResidual.h"
25 #include "btConjugateGradient.h"
26 struct btCollisionObjectWrapper;
27 class btDeformableBackwardEulerObjective;
28 class btDeformableMultiBodyDynamicsWorld;
29
30 class btDeformableBodySolver : public btSoftBodySolver
31 {
32 typedef btAlignedObjectArray<btVector3> TVStack;
33
34 protected:
35 int m_numNodes; // total number of deformable body nodes
36 TVStack m_dv; // v_{n+1} - v_n
37 TVStack m_backup_dv; // backed up dv
38 TVStack m_ddv; // incremental dv
39 TVStack m_residual; // rhs of the linear solve
40 btAlignedObjectArray<btSoftBody*> m_softBodies; // all deformable bodies
41 TVStack m_backupVelocity; // backed up v, equals v_n for implicit, equals v_{n+1}^* for explicit
42 btScalar m_dt; // dt
43 btConjugateGradient<btDeformableBackwardEulerObjective> m_cg; // CG solver
44 btConjugateResidual<btDeformableBackwardEulerObjective> m_cr; // CR solver
45 bool m_implicit; // use implicit scheme if true, explicit scheme if false
46 int m_maxNewtonIterations; // max number of newton iterations
47 btScalar m_newtonTolerance; // stop newton iterations if f(x) < m_newtonTolerance
48 bool m_lineSearch; // If true, use newton's method with line search under implicit scheme
49 public:
50 // handles data related to objective function
51 btDeformableBackwardEulerObjective* m_objective;
52 bool m_useProjection;
53
54 btDeformableBodySolver();
55
56 virtual ~btDeformableBodySolver();
57
58 virtual SolverTypes getSolverType() const
59 {
60 return DEFORMABLE_SOLVER;
61 }
62
63 // update soft body normals
64 virtual void updateSoftBodies();
65
66 virtual btScalar solveContactConstraints(btCollisionObject** deformableBodies, int numDeformableBodies, const btContactSolverInfo& infoGlobal);
67
68 // solve the momentum equation
69 virtual void solveDeformableConstraints(btScalar solverdt);
70
71 // resize/clear data structures
72 void reinitialize(const btAlignedObjectArray<btSoftBody*>& softBodies, btScalar dt);
73
74 // set up contact constraints
75 void setConstraints(const btContactSolverInfo& infoGlobal);
76
77 // add in elastic forces and gravity to obtain v_{n+1}^* and calls predictDeformableMotion
78 virtual void predictMotion(btScalar solverdt);
79
80 // move to temporary position x_{n+1}^* = x_n + dt * v_{n+1}^*
81 // x_{n+1}^* is stored in m_q
82 void predictDeformableMotion(btSoftBody* psb, btScalar dt);
83
84 // save the current velocity to m_backupVelocity
85 void backupVelocity();
86
87 // set m_dv and m_backupVelocity to desired value to prepare for momentum solve
88 void setupDeformableSolve(bool implicit);
89
90 // set the current velocity to that backed up in m_backupVelocity
91 void revertVelocity();
92
93 // set velocity to m_dv + m_backupVelocity
94 void updateVelocity();
95
96 // update the node count
97 bool updateNodes();
98
99 // calculate the change in dv resulting from the momentum solve
100 void computeStep(TVStack& ddv, const TVStack& residual);
101
102 // calculate the change in dv resulting from the momentum solve when line search is turned on
103 btScalar computeDescentStep(TVStack& ddv, const TVStack& residual, bool verbose = false);
104
105 virtual void copySoftBodyToVertexBuffer(const btSoftBody* const softBody, btVertexBufferDescriptor* vertexBuffer) {}
106
107 // process collision between deformable and rigid
108 virtual void processCollision(btSoftBody* softBody, const btCollisionObjectWrapper* collisionObjectWrap)
109 {
110 softBody->defaultCollisionHandler(collisionObjectWrap);
111 }
112
113 // process collision between deformable and deformable
114 virtual void processCollision(btSoftBody* softBody, btSoftBody* otherSoftBody)
115 {
116 softBody->defaultCollisionHandler(otherSoftBody);
117 }
118
119 // If true, implicit time stepping scheme is used.
120 // Otherwise, explicit time stepping scheme is used
121 void setImplicit(bool implicit);
122
123 // If true, newton's method with line search is used when implicit time stepping scheme is turned on
124 void setLineSearch(bool lineSearch);
125
126 // set temporary position x^* = x_n + dt * v
127 // update the deformation gradient at position x^*
128 void updateState();
129
130 // set dv = dv + scale * ddv
131 void updateDv(btScalar scale = 1);
132
133 // set temporary position x^* = x_n + dt * v^*
134 void updateTempPosition();
135
136 // save the current dv to m_backup_dv;
137 void backupDv();
138
139 // set dv to the backed-up value
140 void revertDv();
141
142 // set dv = dv + scale * ddv
143 // set v^* = v_n + dv
144 // set temporary position x^* = x_n + dt * v^*
145 // update the deformation gradient at position x^*
146 void updateEnergy(btScalar scale);
147
148 // calculates the appropriately scaled kinetic energy in the system, which is
149 // 1/2 * dv^T * M * dv
150 // used in line search
151 btScalar kineticEnergy();
152
153 // unused functions
154 virtual void optimize(btAlignedObjectArray<btSoftBody*>& softBodies, bool forceUpdate = false) {}
155 virtual void solveConstraints(btScalar dt) {}
156 virtual bool checkInitialized() { return true; }
157 virtual void copyBackToSoftBodies(bool bMove = true) {}
158 };
159
160 #endif /* btDeformableBodySolver_h */
btCollisionObject
btCollisionObject can be used to manage collision detection objects.
Definition: btCollisionObject.h:50
btDeformableBodySolver::setupDeformableSolve
void setupDeformableSolve(bool implicit)
Definition: btDeformableBodySolver.cpp:329
btConjugateResidual.h
btDeformableBodySolver::m_ddv
TVStack m_ddv
Definition: btDeformableBodySolver.h:38
btDeformableBodySolver::updateSoftBodies
virtual void updateSoftBodies()
Perform necessary per-step updates of soft bodies such as recomputing normals and bounding boxes.
Definition: btDeformableBodySolver.cpp:484
btConjugateGradient.h
btDeformableBodySolver::computeDescentStep
btScalar computeDescentStep(TVStack &ddv, const TVStack &residual, bool verbose=false)
Definition: btDeformableBodySolver.cpp:165
btContactSolverInfo
Definition: btContactSolverInfo.h:76
btSoftBodySolvers.h
btDeformableBodySolver::m_backupVelocity
TVStack m_backupVelocity
Definition: btDeformableBodySolver.h:41
btScalar
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:314
btDeformableBodySolver::kineticEnergy
btScalar kineticEnergy()
Definition: btDeformableBodySolver.cpp:121
btSoftBody::defaultCollisionHandler
void defaultCollisionHandler(const btCollisionObjectWrapper *pcoWrap)
Definition: btSoftBody.cpp:4058
btCollisionObjectWrapper
Definition: btCollisionObjectWrapper.h:18
btDeformableBodySolver::revertDv
void revertDv()
Definition: btDeformableBodySolver.cpp:148
btDeformableBodySolver::processCollision
virtual void processCollision(btSoftBody *softBody, btSoftBody *otherSoftBody)
Process a collision between two soft bodies.
Definition: btDeformableBodySolver.h:114
btDeformableBodySolver::updateEnergy
void updateEnergy(btScalar scale)
Definition: btDeformableBodySolver.cpp:156
btDeformableBodySolver::reinitialize
void reinitialize(const btAlignedObjectArray< btSoftBody * > &softBodies, btScalar dt)
Definition: btDeformableBodySolver.cpp:221
btConjugateGradient< btDeformableBackwardEulerObjective >
btDeformableBodySolver::updateDv
void updateDv(btScalar scale=1)
Definition: btDeformableBodySolver.cpp:205
btDeformableBodySolver::m_numNodes
int m_numNodes
Definition: btDeformableBodySolver.h:35
btDeformableBodySolver::btDeformableBodySolver
btDeformableBodySolver()
Definition: btDeformableBodySolver.cpp:22
btDeformableBodySolver::copyBackToSoftBodies
virtual void copyBackToSoftBodies(bool bMove=true)
Copy necessary data back to the original soft body source objects.
Definition: btDeformableBodySolver.h:157
btDeformableBackwardEulerObjective
Definition: btDeformableBackwardEulerObjective.h:32
btDeformableBodySolver::optimize
virtual void optimize(btAlignedObjectArray< btSoftBody * > &softBodies, bool forceUpdate=false)
Optimize soft bodies in this solver.
Definition: btDeformableBodySolver.h:154
btDeformableBodySolver::setLineSearch
void setLineSearch(bool lineSearch)
Definition: btDeformableBodySolver.cpp:503
btDeformableBodySolver::m_backup_dv
TVStack m_backup_dv
Definition: btDeformableBodySolver.h:37
btDeformableBodySolver::m_cr
btConjugateResidual< btDeformableBackwardEulerObjective > m_cr
Definition: btDeformableBodySolver.h:44
btSoftBodySolver::DEFORMABLE_SOLVER
@ DEFORMABLE_SOLVER
Definition: btSoftBodySolvers.h:39
btDeformableBodySolver::TVStack
btAlignedObjectArray< btVector3 > TVStack
Definition: btDeformableBodySolver.h:32
btDeformableBodySolver::solveConstraints
virtual void solveConstraints(btScalar dt)
Solve constraints for a set of soft bodies.
Definition: btDeformableBodySolver.h:155
btDeformableBodySolver::copySoftBodyToVertexBuffer
virtual void copySoftBodyToVertexBuffer(const btSoftBody *const softBody, btVertexBufferDescriptor *vertexBuffer)
Definition: btDeformableBodySolver.h:105
btMultiBodyLinkCollider.h
btSoftBodySolver::SolverTypes
SolverTypes
Definition: btSoftBodySolvers.h:32
btDeformableBodySolver::backupVelocity
void backupVelocity()
Definition: btDeformableBodySolver.cpp:316
btDeformableMultiBodyDynamicsWorld.h
btDeformableBodySolver::setConstraints
void setConstraints(const btContactSolverInfo &infoGlobal)
Definition: btDeformableBodySolver.cpp:250
btDeformableBodySolver::m_newtonTolerance
btScalar m_newtonTolerance
Definition: btDeformableBodySolver.h:47
btDeformableBodySolver::computeStep
void computeStep(TVStack &ddv, const TVStack &residual)
Definition: btDeformableBodySolver.cpp:213
btVertexBufferDescriptor
Definition: btSoftBodySolverVertexBuffer.h:20
btDeformableBodySolver::m_implicit
bool m_implicit
Definition: btDeformableBodySolver.h:45
btDeformableBodySolver::m_cg
btConjugateGradient< btDeformableBackwardEulerObjective > m_cg
Definition: btDeformableBodySolver.h:43
btDeformableBodySolver::m_lineSearch
bool m_lineSearch
Definition: btDeformableBodySolver.h:48
btDeformableBodySolver::m_maxNewtonIterations
int m_maxNewtonIterations
Definition: btDeformableBodySolver.h:46
btDeformableBodySolver::m_dv
TVStack m_dv
Definition: btDeformableBodySolver.h:36
btDeformableBodySolver::solveContactConstraints
virtual btScalar solveContactConstraints(btCollisionObject **deformableBodies, int numDeformableBodies, const btContactSolverInfo &infoGlobal)
Definition: btDeformableBodySolver.cpp:256
btDeformableBodySolver::m_useProjection
bool m_useProjection
Definition: btDeformableBodySolver.h:52
btDeformableBodySolver::m_residual
TVStack m_residual
Definition: btDeformableBodySolver.h:39
btDeformableBodySolver::updateNodes
bool updateNodes()
Definition: btDeformableBodySolver.cpp:374
btConjugateResidual< btDeformableBackwardEulerObjective >
btAlignedObjectArray< btVector3 >
btDeformableBodySolver::m_dt
btScalar m_dt
Definition: btDeformableBodySolver.h:42
btDeformableBodySolver::updateVelocity
void updateVelocity()
Definition: btDeformableBodySolver.cpp:263
btDeformableBodySolver::checkInitialized
virtual bool checkInitialized()
Ensure that this solver is initialized.
Definition: btDeformableBodySolver.h:156
btDeformableBodySolver::updateTempPosition
void updateTempPosition()
Definition: btDeformableBodySolver.cpp:296
btSoftBody
The btSoftBody is an class to simulate cloth and volumetric soft bodies.
Definition: btSoftBody.h:75
btDeformableBodySolver::predictMotion
virtual void predictMotion(btScalar solverdt)
Predict motion of soft bodies into next timestep.
Definition: btDeformableBodySolver.cpp:387
btSoftBodySolver
Definition: btSoftBodySolvers.h:29
btDeformableBodySolver::m_softBodies
btAlignedObjectArray< btSoftBody * > m_softBodies
Definition: btDeformableBodySolver.h:40
btDeformableBodySolver
Definition: btDeformableBodySolver.h:31
btMultiBodyConstraint.h
btDeformableBodySolver::revertVelocity
void revertVelocity()
Definition: btDeformableBodySolver.cpp:361
btDeformableBodySolver::updateState
void updateState()
Definition: btDeformableBodySolver.cpp:199
btDeformableBodySolver::predictDeformableMotion
void predictDeformableMotion(btSoftBody *psb, btScalar dt)
Definition: btDeformableBodySolver.cpp:417
btDeformableBodySolver::m_objective
btDeformableBackwardEulerObjective * m_objective
Definition: btDeformableBodySolver.h:51
btDeformableBodySolver::backupDv
void backupDv()
Definition: btDeformableBodySolver.cpp:139
btDeformableBodySolver::solveDeformableConstraints
virtual void solveDeformableConstraints(btScalar solverdt)
Definition: btDeformableBodySolver.cpp:33
btDeformableBodySolver::setImplicit
void setImplicit(bool implicit)
Definition: btDeformableBodySolver.cpp:497
btDeformableBodySolver::~btDeformableBodySolver
virtual ~btDeformableBodySolver()
Definition: btDeformableBodySolver.cpp:28
btDeformableBackwardEulerObjective.h
btDeformableBodySolver::getSolverType
virtual SolverTypes getSolverType() const
Return the type of the solver.
Definition: btDeformableBodySolver.h:58
btDeformableBodySolver::processCollision
virtual void processCollision(btSoftBody *softBody, const btCollisionObjectWrapper *collisionObjectWrap)
Definition: btDeformableBodySolver.h:108
btDeformableMultiBodyDynamicsWorld
Definition: btDeformableMultiBodyDynamicsWorld.h:38