Bullet Collision Detection & Physics Library
btPreconditioner.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_PRECONDITIONER_H
17 #define BT_PRECONDITIONER_H
18 
20 {
21 public:
23  virtual void operator()(const TVStack& x, TVStack& b) = 0;
24  virtual void reinitialize(bool nodeUpdated) = 0;
25  virtual ~Preconditioner() {}
26 };
27 
29 {
30 public:
31  virtual void operator()(const TVStack& x, TVStack& b)
32  {
33  btAssert(b.size() == x.size());
34  for (int i = 0; i < b.size(); ++i)
35  b[i] = x[i];
36  }
37  virtual void reinitialize(bool nodeUpdated)
38  {
39  }
40 
42 };
43 
45 {
48 
49 public:
51  : m_softBodies(softBodies)
52  {
53  }
54 
55  virtual void reinitialize(bool nodeUpdated)
56  {
57  if (nodeUpdated)
58  {
59  m_inv_mass.clear();
60  for (int i = 0; i < m_softBodies.size(); ++i)
61  {
62  btSoftBody* psb = m_softBodies[i];
63  for (int j = 0; j < psb->m_nodes.size(); ++j)
64  m_inv_mass.push_back(psb->m_nodes[j].m_im);
65  }
66  }
67  }
68 
69  virtual void operator()(const TVStack& x, TVStack& b)
70  {
71  btAssert(b.size() == x.size());
72  btAssert(m_inv_mass.size() <= x.size());
73  for (int i = 0; i < m_inv_mass.size(); ++i)
74  {
75  b[i] = x[i] * m_inv_mass[i];
76  }
77  for (int i = m_inv_mass.size(); i < b.size(); ++i)
78  {
79  b[i] = x[i];
80  }
81  }
82 };
83 
85 {
90  const btScalar& m_dt;
91  const bool& m_implicit;
92 
93 public:
95  : m_softBodies(softBodies), m_projections(projections), m_lf(lf), m_dt(dt), m_implicit(implicit)
96  {
97  }
98 
99  virtual void reinitialize(bool nodeUpdated)
100  {
101  if (nodeUpdated)
102  {
103  int num_nodes = 0;
104  for (int i = 0; i < m_softBodies.size(); ++i)
105  {
106  btSoftBody* psb = m_softBodies[i];
107  num_nodes += psb->m_nodes.size();
108  }
109  m_inv_A.resize(num_nodes);
110  }
112  for (int i = 0; i < m_inv_A.size(); ++i)
113  {
114  // printf("A[%d] = %f, %f, %f \n", i, m_inv_A[i][0], m_inv_A[i][1], m_inv_A[i][2]);
115  for (int d = 0; d < 3; ++d)
116  {
117  m_inv_A[i][d] = (m_inv_A[i][d] == 0) ? 0.0 : 1.0 / m_inv_A[i][d];
118  }
119  }
121  // printf("S.size() = %d \n", m_inv_S.size());
123  for (int i = 0; i < m_inv_S.size(); ++i)
124  {
125  // printf("S[%d] = %f, %f, %f \n", i, m_inv_S[i][0], m_inv_S[i][1], m_inv_S[i][2]);
126  for (int d = 0; d < 3; ++d)
127  {
128  m_inv_S[i][d] = (m_inv_S[i][d] == 0) ? 0.0 : 1.0 / m_inv_S[i][d];
129  }
130  }
131  }
132 
133  void buildDiagonalA(TVStack& diagA) const
134  {
135  size_t counter = 0;
136  for (int i = 0; i < m_softBodies.size(); ++i)
137  {
138  btSoftBody* psb = m_softBodies[i];
139  for (int j = 0; j < psb->m_nodes.size(); ++j)
140  {
141  const btSoftBody::Node& node = psb->m_nodes[j];
142  diagA[counter] = (node.m_im == 0) ? btVector3(0, 0, 0) : btVector3(1.0 / node.m_im, 1.0 / node.m_im, 1.0 / node.m_im);
143  ++counter;
144  }
145  }
146  if (m_implicit)
147  {
148  printf("implicit not implemented\n");
149  btAssert(false);
150  }
151  for (int i = 0; i < m_lf.size(); ++i)
152  {
153  // add damping matrix
154  m_lf[i]->buildDampingForceDifferentialDiagonal(-m_dt, diagA);
155  }
156  }
157 
158  void buildDiagonalS(const TVStack& inv_A, TVStack& diagS)
159  {
160  for (int c = 0; c < m_projections.m_lagrangeMultipliers.size(); ++c)
161  {
162  // S[k,k] = e_k^T * C A_d^-1 C^T * e_k
164  btVector3& t = diagS[c];
165  t.setZero();
166  for (int j = 0; j < lm.m_num_constraints; ++j)
167  {
168  for (int i = 0; i < lm.m_num_nodes; ++i)
169  {
170  for (int d = 0; d < 3; ++d)
171  {
172  t[j] += inv_A[lm.m_indices[i]][d] * lm.m_dirs[j][d] * lm.m_dirs[j][d] * lm.m_weights[i] * lm.m_weights[i];
173  }
174  }
175  }
176  }
177  }
178 //#define USE_FULL_PRECONDITIONER
179 #ifndef USE_FULL_PRECONDITIONER
180  virtual void operator()(const TVStack& x, TVStack& b)
181  {
182  btAssert(b.size() == x.size());
183  for (int i = 0; i < m_inv_A.size(); ++i)
184  {
185  b[i] = x[i] * m_inv_A[i];
186  }
187  int offset = m_inv_A.size();
188  for (int i = 0; i < m_inv_S.size(); ++i)
189  {
190  b[i + offset] = x[i + offset] * m_inv_S[i];
191  }
192  }
193 #else
194  virtual void operator()(const TVStack& x, TVStack& b)
195  {
196  btAssert(b.size() == x.size());
197  int offset = m_inv_A.size();
198 
199  for (int i = 0; i < m_inv_A.size(); ++i)
200  {
201  b[i] = x[i] * m_inv_A[i];
202  }
203 
204  for (int i = 0; i < m_inv_S.size(); ++i)
205  {
206  b[i + offset].setZero();
207  }
208 
209  for (int c = 0; c < m_projections.m_lagrangeMultipliers.size(); ++c)
210  {
212  // C * x
213  for (int d = 0; d < lm.m_num_constraints; ++d)
214  {
215  for (int i = 0; i < lm.m_num_nodes; ++i)
216  {
217  b[offset + c][d] += lm.m_weights[i] * b[lm.m_indices[i]].dot(lm.m_dirs[d]);
218  }
219  }
220  }
221 
222  for (int i = 0; i < m_inv_S.size(); ++i)
223  {
224  b[i + offset] = b[i + offset] * m_inv_S[i];
225  }
226 
227  for (int i = 0; i < m_inv_A.size(); ++i)
228  {
229  b[i].setZero();
230  }
231 
232  for (int c = 0; c < m_projections.m_lagrangeMultipliers.size(); ++c)
233  {
234  // C^T * lambda
236  for (int i = 0; i < lm.m_num_nodes; ++i)
237  {
238  for (int j = 0; j < lm.m_num_constraints; ++j)
239  {
240  b[lm.m_indices[i]] += b[offset + c][j] * lm.m_weights[i] * lm.m_dirs[j];
241  }
242  }
243  }
244 
245  for (int i = 0; i < m_inv_A.size(); ++i)
246  {
247  b[i] = (x[i] - b[i]) * m_inv_A[i];
248  }
249 
250  TVStack t;
251  t.resize(b.size());
252  for (int i = 0; i < m_inv_S.size(); ++i)
253  {
254  t[i + offset] = x[i + offset] * m_inv_S[i];
255  }
256  for (int i = 0; i < m_inv_A.size(); ++i)
257  {
258  t[i].setZero();
259  }
260  for (int c = 0; c < m_projections.m_lagrangeMultipliers.size(); ++c)
261  {
262  // C^T * lambda
264  for (int i = 0; i < lm.m_num_nodes; ++i)
265  {
266  for (int j = 0; j < lm.m_num_constraints; ++j)
267  {
268  t[lm.m_indices[i]] += t[offset + c][j] * lm.m_weights[i] * lm.m_dirs[j];
269  }
270  }
271  }
272  for (int i = 0; i < m_inv_A.size(); ++i)
273  {
274  b[i] += t[i] * m_inv_A[i];
275  }
276 
277  for (int i = 0; i < m_inv_S.size(); ++i)
278  {
279  b[i + offset] -= x[i + offset] * m_inv_S[i];
280  }
281  }
282 #endif
283 };
284 
285 #endif /* BT_PRECONDITIONER_H */
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:314
#define btAssert(x)
Definition: btScalar.h:153
virtual void operator()(const TVStack &x, TVStack &b)
virtual void reinitialize(bool nodeUpdated)
virtual ~DefaultPreconditioner()
const bool & m_implicit
KKTPreconditioner(const btAlignedObjectArray< btSoftBody * > &softBodies, const btDeformableContactProjection &projections, const btAlignedObjectArray< btDeformableLagrangianForce * > &lf, const btScalar &dt, const bool &implicit)
void buildDiagonalA(TVStack &diagA) const
const btAlignedObjectArray< btSoftBody * > & m_softBodies
const btDeformableContactProjection & m_projections
virtual void reinitialize(bool nodeUpdated)
void buildDiagonalS(const TVStack &inv_A, TVStack &diagS)
const btScalar & m_dt
const btAlignedObjectArray< btDeformableLagrangianForce * > & m_lf
virtual void operator()(const TVStack &x, TVStack &b)
const btAlignedObjectArray< btSoftBody * > & m_softBodies
virtual void reinitialize(bool nodeUpdated)
MassPreconditioner(const btAlignedObjectArray< btSoftBody * > &softBodies)
virtual void operator()(const TVStack &x, TVStack &b)
btAlignedObjectArray< btScalar > m_inv_mass
virtual void reinitialize(bool nodeUpdated)=0
btAlignedObjectArray< btVector3 > TVStack
virtual ~Preconditioner()
virtual void operator()(const TVStack &x, TVStack &b)=0
int size() const
return the number of elements in the array
void resize(int newsize, const T &fillData=T())
void clear()
clear the array, deallocated memory. Generally it is better to use array.resize(0),...
void push_back(const T &_Val)
btAlignedObjectArray< LagrangeMultiplier > m_lagrangeMultipliers
The btSoftBody is an class to simulate cloth and volumetric soft bodies.
Definition: btSoftBody.h:75
tNodeArray m_nodes
Definition: btSoftBody.h:812
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:82
void setZero()
Definition: btVector3.h:671