Bullet Collision Detection & Physics Library
btDeformableBackwardEulerObjective.h
Go to the documentation of this file.
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_BACKWARD_EULER_OBJECTIVE_H
17#define BT_BACKWARD_EULER_OBJECTIVE_H
18//#include "btConjugateGradient.h"
27#include "btPreconditioner.h"
30
32{
33public:
45
47
49
50 void initialize() {}
51
52 // compute the rhs for CG solve, i.e, add the dt scaled implicit force to residual
53 void computeResidual(btScalar dt, TVStack& residual);
54
55 // add explicit force to the velocity
56 void applyExplicitForce(TVStack& force);
57
58 // apply force to velocity and optionally reset the force to zero
59 void applyForce(TVStack& force, bool setZero);
60
61 // compute the norm of the residual
62 btScalar computeNorm(const TVStack& residual) const;
63
64 // compute one step of the solve (there is only one solve if the system is linear)
65 void computeStep(TVStack& dv, const TVStack& residual, const btScalar& dt);
66
67 // perform A*x = b
68 void multiply(const TVStack& x, TVStack& b) const;
69
70 // set initial guess for CG solve
71 void initialGuess(TVStack& dv, const TVStack& residual);
72
73 // reset data structure and reset dt
74 void reinitialize(bool nodeUpdated, btScalar dt);
75
76 void setDt(btScalar dt);
77
78 // add friction force to residual
80
81 // add dv to velocity
82 void updateVelocity(const TVStack& dv);
83
84 //set constraints as projections
85 void setConstraints(const btContactSolverInfo& infoGlobal);
86
87 // update the projections and project the residual
89 {
90 BT_PROFILE("project");
92 }
93
94 // perform precondition M^(-1) x = b
95 void precondition(const TVStack& x, TVStack& b)
96 {
97 m_preconditioner->operator()(x, b);
98 }
99
100 // reindex all the vertices
101 virtual void updateId()
102 {
103 size_t node_id = 0;
104 size_t face_id = 0;
105 m_nodes.clear();
106 for (int i = 0; i < m_softBodies.size(); ++i)
107 {
108 btSoftBody* psb = m_softBodies[i];
109 for (int j = 0; j < psb->m_nodes.size(); ++j)
110 {
111 psb->m_nodes[j].index = node_id;
112 m_nodes.push_back(&psb->m_nodes[j]);
113 ++node_id;
114 }
115 for (int j = 0; j < psb->m_faces.size(); ++j)
116 {
117 psb->m_faces[j].m_index = face_id;
118 ++face_id;
119 }
120 }
121 }
122
124 {
125 return &m_nodes;
126 }
127
128 void setImplicit(bool implicit)
129 {
130 m_implicit = implicit;
131 }
132
133 // Calculate the total potential energy in the system
135
136 void addLagrangeMultiplier(const TVStack& vec, TVStack& extended_vec)
137 {
138 extended_vec.resize(vec.size() + m_projection.m_lagrangeMultipliers.size());
139 for (int i = 0; i < vec.size(); ++i)
140 {
141 extended_vec[i] = vec[i];
142 }
143 int offset = vec.size();
144 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
145 {
146 extended_vec[offset + i].setZero();
147 }
148 }
149
150 void addLagrangeMultiplierRHS(const TVStack& residual, const TVStack& m_dv, TVStack& extended_residual)
151 {
152 extended_residual.resize(residual.size() + m_projection.m_lagrangeMultipliers.size());
153 for (int i = 0; i < residual.size(); ++i)
154 {
155 extended_residual[i] = residual[i];
156 }
157 int offset = residual.size();
158 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
159 {
161 extended_residual[offset + i].setZero();
162 for (int d = 0; d < lm.m_num_constraints; ++d)
163 {
164 for (int n = 0; n < lm.m_num_nodes; ++n)
165 {
166 extended_residual[offset + i][d] += lm.m_weights[n] * m_dv[lm.m_indices[n]].dot(lm.m_dirs[d]);
167 }
168 }
169 }
170 }
171
172 void calculateContactForce(const TVStack& dv, const TVStack& rhs, TVStack& f)
173 {
174 size_t counter = 0;
175 for (int i = 0; i < m_softBodies.size(); ++i)
176 {
177 btSoftBody* psb = m_softBodies[i];
178 for (int j = 0; j < psb->m_nodes.size(); ++j)
179 {
180 const btSoftBody::Node& node = psb->m_nodes[j];
181 f[counter] = (node.m_im == 0) ? btVector3(0, 0, 0) : dv[counter] / node.m_im;
182 ++counter;
183 }
184 }
185 for (int i = 0; i < m_lf.size(); ++i)
186 {
187 // add damping matrix
188 m_lf[i]->addScaledDampingForceDifferential(-m_dt, dv, f);
189 }
190 counter = 0;
191 for (; counter < f.size(); ++counter)
192 {
193 f[counter] = rhs[counter] - f[counter];
194 }
195 }
196};
197
198#endif /* btBackwardEulerObjective_h */
#define BT_PROFILE(name)
Definition: btQuickprof.h:198
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:314
int size() const
return the number of elements in the array
void resize(int newsize, const T &fillData=T())
btDeformableBackwardEulerObjective(btAlignedObjectArray< btSoftBody * > &softBodies, const TVStack &backup_v)
void calculateContactForce(const TVStack &dv, const TVStack &rhs, TVStack &f)
void precondition(const TVStack &x, TVStack &b)
void setConstraints(const btContactSolverInfo &infoGlobal)
void computeResidual(btScalar dt, TVStack &residual)
btAlignedObjectArray< btDeformableLagrangianForce * > m_lf
btAlignedObjectArray< btSoftBody::Node * > m_nodes
void addLagrangeMultiplier(const TVStack &vec, TVStack &extended_vec)
btAlignedObjectArray< btSoftBody * > & m_softBodies
void computeStep(TVStack &dv, const TVStack &residual, const btScalar &dt)
const btAlignedObjectArray< btSoftBody::Node * > * getIndices() const
void initialGuess(TVStack &dv, const TVStack &residual)
btScalar computeNorm(const TVStack &residual) const
void multiply(const TVStack &x, TVStack &b) const
void reinitialize(bool nodeUpdated, btScalar dt)
void addLagrangeMultiplierRHS(const TVStack &residual, const TVStack &m_dv, TVStack &extended_residual)
btAlignedObjectArray< LagrangeMultiplier > m_lagrangeMultipliers
The btSoftBody is an class to simulate cloth and volumetric soft bodies.
Definition: btSoftBody.h:75
tFaceArray m_faces
Definition: btSoftBody.h:817
tNodeArray m_nodes
Definition: btSoftBody.h:814
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:82