2 Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
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.
16 #ifndef BT_BACKWARD_EULER_OBJECTIVE_H
17 #define BT_BACKWARD_EULER_OBJECTIVE_H
18 //#include "btConjugateGradient.h"
19 #include "btDeformableLagrangianForce.h"
20 #include "btDeformableMassSpringForce.h"
21 #include "btDeformableGravityForce.h"
22 #include "btDeformableCorotatedForce.h"
23 #include "btDeformableMousePickingForce.h"
24 #include "btDeformableLinearElasticityForce.h"
25 #include "btDeformableNeoHookeanForce.h"
26 #include "btDeformableContactProjection.h"
27 #include "btPreconditioner.h"
28 // #include "btDeformableMultiBodyDynamicsWorld.h"
29 #include "LinearMath/btQuickprof.h"
31 class btDeformableBackwardEulerObjective
40 typedef btAlignedObjectArray<btVector3> TVStack;
42 btAlignedObjectArray<btDeformableLagrangianForce*> m_lf;
43 btAlignedObjectArray<btSoftBody*>& m_softBodies;
44 Preconditioner* m_preconditioner;
45 btDeformableContactProjection m_projection;
46 const TVStack& m_backupVelocity;
47 btAlignedObjectArray<btSoftBody::Node*> m_nodes;
49 MassPreconditioner* m_massPreconditioner;
50 KKTPreconditioner* m_KKTPreconditioner;
52 btDeformableBackwardEulerObjective(btAlignedObjectArray<btSoftBody*>& softBodies, const TVStack& backup_v);
54 virtual ~btDeformableBackwardEulerObjective();
58 // compute the rhs for CG solve, i.e, add the dt scaled implicit force to residual
59 void computeResidual(btScalar dt, TVStack& residual);
61 // add explicit force to the velocity
62 void applyExplicitForce(TVStack& force);
64 // apply force to velocity and optionally reset the force to zero
65 void applyForce(TVStack& force, bool setZero);
67 // compute the norm of the residual
68 btScalar computeNorm(const TVStack& residual) const;
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);
74 void multiply(const TVStack& x, TVStack& b) const;
76 // set initial guess for CG solve
77 void initialGuess(TVStack& dv, const TVStack& residual);
79 // reset data structure and reset dt
80 void reinitialize(bool nodeUpdated, btScalar dt);
82 void setDt(btScalar dt);
84 // add friction force to residual
85 void applyDynamicFriction(TVStack& r);
88 void updateVelocity(const TVStack& dv);
90 //set constraints as projections
91 void setConstraints(const btContactSolverInfo& infoGlobal);
93 // update the projections and project the residual
94 void project(TVStack& r)
96 BT_PROFILE("project");
97 m_projection.project(r);
100 // perform precondition M^(-1) x = b
101 void precondition(const TVStack& x, TVStack& b)
103 m_preconditioner->operator()(x, b);
106 // reindex all the vertices
107 virtual void updateId()
112 for (int i = 0; i < m_softBodies.size(); ++i)
114 btSoftBody* psb = m_softBodies[i];
115 for (int j = 0; j < psb->m_nodes.size(); ++j)
117 psb->m_nodes[j].index = node_id;
118 m_nodes.push_back(&psb->m_nodes[j]);
121 for (int j = 0; j < psb->m_faces.size(); ++j)
123 psb->m_faces[j].m_index = face_id;
129 const btAlignedObjectArray<btSoftBody::Node*>* getIndices() const
134 void setImplicit(bool implicit)
136 m_implicit = implicit;
139 // Calculate the total potential energy in the system
140 btScalar totalEnergy(btScalar dt);
142 void addLagrangeMultiplier(const TVStack& vec, TVStack& extended_vec)
144 extended_vec.resize(vec.size() + m_projection.m_lagrangeMultipliers.size());
145 for (int i = 0; i < vec.size(); ++i)
147 extended_vec[i] = vec[i];
149 int offset = vec.size();
150 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
152 extended_vec[offset + i].setZero();
156 void addLagrangeMultiplierRHS(const TVStack& residual, const TVStack& m_dv, TVStack& extended_residual)
158 extended_residual.resize(residual.size() + m_projection.m_lagrangeMultipliers.size());
159 for (int i = 0; i < residual.size(); ++i)
161 extended_residual[i] = residual[i];
163 int offset = residual.size();
164 for (int i = 0; i < m_projection.m_lagrangeMultipliers.size(); ++i)
166 const LagrangeMultiplier& lm = m_projection.m_lagrangeMultipliers[i];
167 extended_residual[offset + i].setZero();
168 for (int d = 0; d < lm.m_num_constraints; ++d)
170 for (int n = 0; n < lm.m_num_nodes; ++n)
172 extended_residual[offset + i][d] += lm.m_weights[n] * m_dv[lm.m_indices[n]].dot(lm.m_dirs[d]);
178 void calculateContactForce(const TVStack& dv, const TVStack& rhs, TVStack& f)
181 for (int i = 0; i < m_softBodies.size(); ++i)
183 btSoftBody* psb = m_softBodies[i];
184 for (int j = 0; j < psb->m_nodes.size(); ++j)
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;
191 for (int i = 0; i < m_lf.size(); ++i)
193 // add damping matrix
194 m_lf[i]->addScaledDampingForceDifferential(-m_dt, dv, f);
197 for (; counter < f.size(); ++counter)
199 f[counter] = rhs[counter] - f[counter];
204 #endif /* btBackwardEulerObjective_h */