Bullet Collision Detection & Physics Library: btDeformableBackwardEulerObjective.cpp Source File

Bullet Collision Detection & Physics Library

btDeformableBackwardEulerObjective.cpp
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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 #include "btDeformableBackwardEulerObjective.h"
17 #include "btPreconditioner.h"
18 #include "LinearMath/btQuickprof.h"
19
20 btDeformableBackwardEulerObjective::btDeformableBackwardEulerObjective(btAlignedObjectArray<btSoftBody*>& softBodies, const TVStack& backup_v)
21 : m_softBodies(softBodies), m_projection(softBodies), m_backupVelocity(backup_v), m_implicit(false)
22 {
23 m_massPreconditioner = new MassPreconditioner(m_softBodies);
24 m_KKTPreconditioner = new KKTPreconditioner(m_softBodies, m_projection, m_lf, m_dt, m_implicit);
25 m_preconditioner = m_KKTPreconditioner;
26 }
27
28 btDeformableBackwardEulerObjective::~btDeformableBackwardEulerObjective()
29 {
30 delete m_KKTPreconditioner;
31 delete m_massPreconditioner;
32 }
33
34 void btDeformableBackwardEulerObjective::reinitialize(bool nodeUpdated, btScalar dt)
35 {
36 BT_PROFILE("reinitialize");
37 if (dt > 0)
38 {
39 setDt(dt);
40 }
41 if (nodeUpdated)
42 {
43 updateId();
44 }
45 for (int i = 0; i < m_lf.size(); ++i)
46 {
47 m_lf[i]->reinitialize(nodeUpdated);
48 }
49 btMatrix3x3 I;
50 I.setIdentity();
51 for (int i = 0; i < m_softBodies.size(); ++i)
52 {
53 btSoftBody* psb = m_softBodies[i];
54 for (int j = 0; j < psb->m_nodes.size(); ++j)
55 {
56 if (psb->m_nodes[j].m_im > 0)
57 psb->m_nodes[j].m_effectiveMass = I * (1.0 / psb->m_nodes[j].m_im);
58 }
59 }
60 m_projection.reinitialize(nodeUpdated);
61 // m_preconditioner->reinitialize(nodeUpdated);
62 }
63
64 void btDeformableBackwardEulerObjective::setDt(btScalar dt)
65 {
66 m_dt = dt;
67 }
68
69 void btDeformableBackwardEulerObjective::multiply(const TVStack& x, TVStack& b) const
70 {
71 BT_PROFILE("multiply");
72 // add in the mass term
73 size_t counter = 0;
74 for (int i = 0; i < m_softBodies.size(); ++i)
75 {
76 btSoftBody* psb = m_softBodies[i];
77 for (int j = 0; j < psb->m_nodes.size(); ++j)
78 {
79 const btSoftBody::Node& node = psb->m_nodes[j];
80 b[counter] = (node.m_im == 0) ? btVector3(0, 0, 0) : x[counter] / node.m_im;
81 ++counter;
82 }
83 }
84
85 for (int i = 0; i < m_lf.size(); ++i)
86 {
87 // add damping matrix
88 m_lf[i]->addScaledDampingForceDifferential(-m_dt, x, b);
89 // Always integrate picking force implicitly for stability.
90 if (m_implicit || m_lf[i]->getForceType() == BT_MOUSE_PICKING_FORCE)
91 {
92 m_lf[i]->addScaledElasticForceDifferential(-m_dt * m_dt, x, b);
93 }
94 }
95 int offset = m_nodes.size();
96 for (int i = offset; i < b.size(); ++i)
97 {
98 b[i].setZero();
99 }
100 // add in the lagrange multiplier terms
101
102 for (int c = 0; c < m_projection.m_lagrangeMultipliers.size(); ++c)
103 {
104 // C^T * lambda
105 const LagrangeMultiplier& lm = m_projection.m_lagrangeMultipliers[c];
106 for (int i = 0; i < lm.m_num_nodes; ++i)
107 {
108 for (int j = 0; j < lm.m_num_constraints; ++j)
109 {
110 b[lm.m_indices[i]] += x[offset + c][j] * lm.m_weights[i] * lm.m_dirs[j];
111 }
112 }
113 // C * x
114 for (int d = 0; d < lm.m_num_constraints; ++d)
115 {
116 for (int i = 0; i < lm.m_num_nodes; ++i)
117 {
118 b[offset + c][d] += lm.m_weights[i] * x[lm.m_indices[i]].dot(lm.m_dirs[d]);
119 }
120 }
121 }
122 }
123
124 void btDeformableBackwardEulerObjective::updateVelocity(const TVStack& dv)
125 {
126 for (int i = 0; i < m_softBodies.size(); ++i)
127 {
128 btSoftBody* psb = m_softBodies[i];
129 for (int j = 0; j < psb->m_nodes.size(); ++j)
130 {
131 btSoftBody::Node& node = psb->m_nodes[j];
132 node.m_v = m_backupVelocity[node.index] + dv[node.index];
133 }
134 }
135 }
136
137 void btDeformableBackwardEulerObjective::applyForce(TVStack& force, bool setZero)
138 {
139 size_t counter = 0;
140 for (int i = 0; i < m_softBodies.size(); ++i)
141 {
142 btSoftBody* psb = m_softBodies[i];
143 if (!psb->isActive())
144 {
145 counter += psb->m_nodes.size();
146 continue;
147 }
148 if (m_implicit)
149 {
150 for (int j = 0; j < psb->m_nodes.size(); ++j)
151 {
152 if (psb->m_nodes[j].m_im != 0)
153 {
154 psb->m_nodes[j].m_v += psb->m_nodes[j].m_effectiveMass_inv * force[counter++];
155 }
156 }
157 }
158 else
159 {
160 for (int j = 0; j < psb->m_nodes.size(); ++j)
161 {
162 btScalar one_over_mass = (psb->m_nodes[j].m_im == 0) ? 0 : psb->m_nodes[j].m_im;
163 psb->m_nodes[j].m_v += one_over_mass * force[counter++];
164 }
165 }
166 }
167 if (setZero)
168 {
169 for (int i = 0; i < force.size(); ++i)
170 force[i].setZero();
171 }
172 }
173
174 void btDeformableBackwardEulerObjective::computeResidual(btScalar dt, TVStack& residual)
175 {
176 BT_PROFILE("computeResidual");
177 // add implicit force
178 for (int i = 0; i < m_lf.size(); ++i)
179 {
180 // Always integrate picking force implicitly for stability.
181 if (m_implicit || m_lf[i]->getForceType() == BT_MOUSE_PICKING_FORCE)
182 {
183 m_lf[i]->addScaledForces(dt, residual);
184 }
185 else
186 {
187 m_lf[i]->addScaledDampingForce(dt, residual);
188 }
189 }
190 // m_projection.project(residual);
191 }
192
193 btScalar btDeformableBackwardEulerObjective::computeNorm(const TVStack& residual) const
194 {
195 btScalar mag = 0;
196 for (int i = 0; i < residual.size(); ++i)
197 {
198 mag += residual[i].length2();
199 }
200 return std::sqrt(mag);
201 }
202
203 btScalar btDeformableBackwardEulerObjective::totalEnergy(btScalar dt)
204 {
205 btScalar e = 0;
206 for (int i = 0; i < m_lf.size(); ++i)
207 {
208 e += m_lf[i]->totalEnergy(dt);
209 }
210 return e;
211 }
212
213 void btDeformableBackwardEulerObjective::applyExplicitForce(TVStack& force)
214 {
215 for (int i = 0; i < m_softBodies.size(); ++i)
216 {
217 m_softBodies[i]->advanceDeformation();
218 }
219 if (m_implicit)
220 {
221 // apply forces except gravity force
222 btVector3 gravity;
223 for (int i = 0; i < m_lf.size(); ++i)
224 {
225 if (m_lf[i]->getForceType() == BT_GRAVITY_FORCE)
226 {
227 gravity = static_cast<btDeformableGravityForce*>(m_lf[i])->m_gravity;
228 }
229 else
230 {
231 m_lf[i]->addScaledForces(m_dt, force);
232 }
233 }
234 for (int i = 0; i < m_lf.size(); ++i)
235 {
236 m_lf[i]->addScaledHessian(m_dt);
237 }
238 for (int i = 0; i < m_softBodies.size(); ++i)
239 {
240 btSoftBody* psb = m_softBodies[i];
241 if (psb->isActive())
242 {
243 for (int j = 0; j < psb->m_nodes.size(); ++j)
244 {
245 // add gravity explicitly
246 psb->m_nodes[j].m_v += m_dt * psb->m_gravityFactor * gravity;
247 }
248 }
249 }
250 }
251 else
252 {
253 for (int i = 0; i < m_lf.size(); ++i)
254 {
255 m_lf[i]->addScaledExplicitForce(m_dt, force);
256 }
257 }
258 // calculate inverse mass matrix for all nodes
259 for (int i = 0; i < m_softBodies.size(); ++i)
260 {
261 btSoftBody* psb = m_softBodies[i];
262 if (psb->isActive())
263 {
264 for (int j = 0; j < psb->m_nodes.size(); ++j)
265 {
266 if (psb->m_nodes[j].m_im > 0)
267 {
268 psb->m_nodes[j].m_effectiveMass_inv = psb->m_nodes[j].m_effectiveMass.inverse();
269 }
270 }
271 }
272 }
273 applyForce(force, true);
274 }
275
276 void btDeformableBackwardEulerObjective::initialGuess(TVStack& dv, const TVStack& residual)
277 {
278 size_t counter = 0;
279 for (int i = 0; i < m_softBodies.size(); ++i)
280 {
281 btSoftBody* psb = m_softBodies[i];
282 for (int j = 0; j < psb->m_nodes.size(); ++j)
283 {
284 dv[counter] = psb->m_nodes[j].m_im * residual[counter];
285 ++counter;
286 }
287 }
288 }
289
290 //set constraints as projections
291 void btDeformableBackwardEulerObjective::setConstraints(const btContactSolverInfo& infoGlobal)
292 {
293 m_projection.setConstraints(infoGlobal);
294 }
295
296 void btDeformableBackwardEulerObjective::applyDynamicFriction(TVStack& r)
297 {
298 m_projection.applyDynamicFriction(r);
299 }
LagrangeMultiplier::m_num_constraints
int m_num_constraints
Definition: btDeformableContactProjection.h:30
btDeformableBackwardEulerObjective::m_lf
btAlignedObjectArray< btDeformableLagrangianForce * > m_lf
Definition: btDeformableBackwardEulerObjective.h:36
btDeformableContactProjection::reinitialize
virtual void reinitialize(bool nodeUpdated)
Definition: btDeformableContactProjection.cpp:614
btSoftBody::m_gravityFactor
btScalar m_gravityFactor
Definition: btSoftBody.h:842
btContactSolverInfo
Definition: btContactSolverInfo.h:76
btScalar
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:314
BT_GRAVITY_FORCE
@ BT_GRAVITY_FORCE
Definition: btDeformableLagrangianForce.h:25
btDeformableBackwardEulerObjective::setDt
void setDt(btScalar dt)
Definition: btDeformableBackwardEulerObjective.cpp:64
btDeformableBackwardEulerObjective::applyForce
void applyForce(TVStack &force, bool setZero)
Definition: btDeformableBackwardEulerObjective.cpp:137
btDeformableBackwardEulerObjective::m_implicit
bool m_implicit
Definition: btDeformableBackwardEulerObjective.h:42
btDeformableBackwardEulerObjective::m_projection
btDeformableContactProjection m_projection
Definition: btDeformableBackwardEulerObjective.h:39
btDeformableBackwardEulerObjective::btDeformableBackwardEulerObjective
btDeformableBackwardEulerObjective(btAlignedObjectArray< btSoftBody * > &softBodies, const TVStack &backup_v)
Definition: btDeformableBackwardEulerObjective.cpp:20
LagrangeMultiplier::m_dirs
btVector3 m_dirs[3]
Definition: btDeformableContactProjection.h:33
btDeformableContactProjection::applyDynamicFriction
virtual void applyDynamicFriction(TVStack &f)
Definition: btDeformableContactProjection.cpp:563
btDeformableBackwardEulerObjective::m_dt
btScalar m_dt
Definition: btDeformableBackwardEulerObjective.h:35
btDeformableBackwardEulerObjective::reinitialize
void reinitialize(bool nodeUpdated, btScalar dt)
Definition: btDeformableBackwardEulerObjective.cpp:34
btDeformableBackwardEulerObjective::m_preconditioner
Preconditioner * m_preconditioner
Definition: btDeformableBackwardEulerObjective.h:38
btDeformableBackwardEulerObjective::setConstraints
void setConstraints(const btContactSolverInfo &infoGlobal)
Definition: btDeformableBackwardEulerObjective.cpp:291
btSoftBody::Node
Definition: btSoftBody.h:268
BT_MOUSE_PICKING_FORCE
@ BT_MOUSE_PICKING_FORCE
Definition: btDeformableLagrangianForce.h:30
btDeformableBackwardEulerObjective::applyDynamicFriction
void applyDynamicFriction(TVStack &r)
Definition: btDeformableBackwardEulerObjective.cpp:296
btDeformableBackwardEulerObjective::updateId
virtual void updateId()
Definition: btDeformableBackwardEulerObjective.h:101
btDeformableContactProjection::m_lagrangeMultipliers
btAlignedObjectArray< LagrangeMultiplier > m_lagrangeMultipliers
Definition: btDeformableContactProjection.h:52
btDeformableBackwardEulerObjective::m_KKTPreconditioner
KKTPreconditioner * m_KKTPreconditioner
Definition: btDeformableBackwardEulerObjective.h:44
btDeformableBackwardEulerObjective::updateVelocity
void updateVelocity(const TVStack &dv)
Definition: btDeformableBackwardEulerObjective.cpp:124
btDeformableBackwardEulerObjective::computeResidual
void computeResidual(btScalar dt, TVStack &residual)
Definition: btDeformableBackwardEulerObjective.cpp:174
LagrangeMultiplier::m_num_nodes
int m_num_nodes
Definition: btDeformableContactProjection.h:31
btDeformableBackwardEulerObjective::m_softBodies
btAlignedObjectArray< btSoftBody * > & m_softBodies
Definition: btDeformableBackwardEulerObjective.h:37
btMatrix3x3
The btMatrix3x3 class implements a 3x3 rotation matrix, to perform linear algebra in combination with...
Definition: btMatrix3x3.h:50
btDeformableBackwardEulerObjective::computeNorm
btScalar computeNorm(const TVStack &residual) const
Definition: btDeformableBackwardEulerObjective.cpp:193
btDeformableBackwardEulerObjective::m_massPreconditioner
MassPreconditioner * m_massPreconditioner
Definition: btDeformableBackwardEulerObjective.h:43
btVector3
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:82
btSoftBody::Node::index
int index
Definition: btSoftBody.h:280
btDeformableBackwardEulerObjective::initialGuess
void initialGuess(TVStack &dv, const TVStack &residual)
Definition: btDeformableBackwardEulerObjective.cpp:276
btAlignedObjectArray< btSoftBody * >
LagrangeMultiplier::m_indices
int m_indices[3]
Definition: btDeformableContactProjection.h:34
KKTPreconditioner
Definition: btPreconditioner.h:85
btDeformableBackwardEulerObjective::~btDeformableBackwardEulerObjective
virtual ~btDeformableBackwardEulerObjective()
Definition: btDeformableBackwardEulerObjective.cpp:28
btDeformableGravityForce
Definition: btDeformableGravityForce.h:22
btDeformableBackwardEulerObjective::multiply
void multiply(const TVStack &x, TVStack &b) const
Definition: btDeformableBackwardEulerObjective.cpp:69
btSoftBody
The btSoftBody is an class to simulate cloth and volumetric soft bodies.
Definition: btSoftBody.h:75
btDeformableBackwardEulerObjective::totalEnergy
btScalar totalEnergy(btScalar dt)
Definition: btDeformableBackwardEulerObjective.cpp:203
btDeformableBackwardEulerObjective::m_backupVelocity
const TVStack & m_backupVelocity
Definition: btDeformableBackwardEulerObjective.h:40
btQuickprof.h
btCollisionObject::isActive
bool isActive() const
Definition: btCollisionObject.h:305
btMatrix3x3::setIdentity
void setIdentity()
Set the matrix to the identity.
Definition: btMatrix3x3.h:323
btDeformableBackwardEulerObjective::applyExplicitForce
void applyExplicitForce(TVStack &force)
Definition: btDeformableBackwardEulerObjective.cpp:213
LagrangeMultiplier::m_weights
btScalar m_weights[3]
Definition: btDeformableContactProjection.h:32
btDeformableBackwardEulerObjective::m_nodes
btAlignedObjectArray< btSoftBody::Node * > m_nodes
Definition: btDeformableBackwardEulerObjective.h:41
MassPreconditioner
Definition: btPreconditioner.h:45
LagrangeMultiplier
Definition: btDeformableContactProjection.h:29
btSoftBody::Node::m_im
btScalar m_im
Definition: btSoftBody.h:275
btSoftBody::Node::m_v
btVector3 m_v
Definition: btSoftBody.h:271
btPreconditioner.h
BT_PROFILE
#define BT_PROFILE(name)
Definition: btQuickprof.h:198
btDeformableBackwardEulerObjective.h
btDeformableContactProjection::setConstraints
virtual void setConstraints(const btContactSolverInfo &infoGlobal)
Definition: btDeformableContactProjection.cpp:90
btAlignedObjectArray::size
int size() const
return the number of elements in the array
Definition: btAlignedObjectArray.h:142
btSoftBody::m_nodes
tNodeArray m_nodes
Definition: btSoftBody.h:812