Bullet Collision Detection & Physics Library
btDeformableBackwardEulerObjective.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_BACKWARD_EULER_OBJECTIVE_H
17#define BT_BACKWARD_EULER_OBJECTIVE_H
18//#include "btConjugateGradient.h"
27#include "btPreconditioner.h"
28// #include "btDeformableMultiBodyDynamicsWorld.h"
30
32{
33public:
34 enum _
35 {
38 };
39
51
53
55
56 void initialize() {}
57
58 // compute the rhs for CG solve, i.e, add the dt scaled implicit force to residual
60
61 // add explicit force to the velocity
63
64 // apply force to velocity and optionally reset the force to zero
65 void applyForce(TVStack& force, bool setZero);
66
67 // compute the norm of the residual
69
70 // compute one step of the solve (there is only one solve if the system is linear)
71 void computeStep(TVStack& dv, const TVStack& residual, const btScalar& dt);
72
73 // perform A*x = b
74 void multiply(const TVStack& x, TVStack& b) const;
75
76 // set initial guess for CG solve
77 void initialGuess(TVStack& dv, const TVStack& residual);
78
79 // reset data structure and reset dt
80 void reinitialize(bool nodeUpdated, btScalar dt);
81
82 void setDt(btScalar dt);
83
84 // add friction force to residual
86
87 // add dv to velocity
88 void updateVelocity(const TVStack& dv);
89
90 //set constraints as projections
92
93 // update the projections and project the residual
95 {
96 BT_PROFILE("project");
98 }
99
100 // perform precondition M^(-1) x = b
101 void precondition(const TVStack& x, TVStack& b)
102 {
103 m_preconditioner->operator()(x, b);
104 }
105
106 // reindex all the vertices
107 virtual void updateId()
108 {
109 size_t node_id = 0;
110 size_t face_id = 0;
111 m_nodes.clear();
112 for (int i = 0; i < m_softBodies.size(); ++i)
113 {
114 btSoftBody* psb = m_softBodies[i];
115 for (int j = 0; j < psb->m_nodes.size(); ++j)
116 {
117 psb->m_nodes[j].index = node_id;
118 m_nodes.push_back(&psb->m_nodes[j]);
119 ++node_id;
120 }
121 for (int j = 0; j < psb->m_faces.size(); ++j)
122 {
123 psb->m_faces[j].m_index = face_id;
124 ++face_id;
125 }
126 }
127 }
128
130 {
131 return &m_nodes;
132 }
133
135 {
137 }
138
139 // Calculate the total potential energy in the system
141
143 {
145 for (int i = 0; i < vec.size(); ++i)
146 {
147 extended_vec[i] = vec[i];
148 }
149 int offset = vec.size();
150 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
151 {
152 extended_vec[offset + i].setZero();
153 }
154 }
155
157 {
159 for (int i = 0; i < residual.size(); ++i)
160 {
162 }
163 int offset = residual.size();
164 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
165 {
167 extended_residual[offset + i].setZero();
168 for (int d = 0; d < lm.m_num_constraints; ++d)
169 {
170 for (int n = 0; n < lm.m_num_nodes; ++n)
171 {
172 extended_residual[offset + i][d] += lm.m_weights[n] * m_dv[lm.m_indices[n]].dot(lm.m_dirs[d]);
173 }
174 }
175 }
176 }
177
178 void calculateContactForce(const TVStack& dv, const TVStack& rhs, TVStack& f)
179 {
180 size_t counter = 0;
181 for (int i = 0; i < m_softBodies.size(); ++i)
182 {
183 btSoftBody* psb = m_softBodies[i];
184 for (int j = 0; j < psb->m_nodes.size(); ++j)
185 {
186 const btSoftBody::Node& node = psb->m_nodes[j];
187 f[counter] = (node.m_im == 0) ? btVector3(0, 0, 0) : dv[counter] / node.m_im;
188 ++counter;
189 }
190 }
191 for (int i = 0; i < m_lf.size(); ++i)
192 {
193 // add damping matrix
194 m_lf[i]->addScaledDampingForceDifferential(-m_dt, dv, f);
195 }
196 counter = 0;
197 for (; counter < f.size(); ++counter)
198 {
199 f[counter] = rhs[counter] - f[counter];
200 }
201 }
202};
203
204#endif /* btBackwardEulerObjective_h */
const T & btMax(const T &a, const T &b)
Definition btMinMax.h:27
#define BT_PROFILE(name)
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition btScalar.h:314
The btAlignedObjectArray template class uses a subset of the stl::vector interface for its methods It...
int size() const
return the number of elements in the array
void clear()
clear the array, deallocated memory. Generally it is better to use array.resize(0),...
void push_back(const T &_Val)
void calculateContactForce(const TVStack &dv, const TVStack &rhs, TVStack &f)
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 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