120 lines
4.5 KiB
C++
120 lines
4.5 KiB
C++
/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2016 Google Inc. http://bulletphysics.org
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This software is provided 'as-is', without any express or implied warranty.
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In no event will the authors be held liable for any damages arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it freely,
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subject to the following restrictions:
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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.
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2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef BT_MASS_SPRING_H
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#define BT_MASS_SPRING_H
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#include "btDeformableLagrangianForce.h"
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class btDeformableMassSpringForce : public btDeformableLagrangianForce
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{
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public:
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// using TVStack = btDeformableLagrangianForce::TVStack;
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typedef btAlignedObjectArray<btVector3> TVStack;
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btDeformableMassSpringForce()
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{
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}
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virtual void addScaledImplicitForce(btScalar scale, TVStack& force)
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{
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addScaledDampingForce(scale, force);
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}
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virtual void addScaledExplicitForce(btScalar scale, TVStack& force)
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{
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addScaledElasticForce(scale, force);
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}
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virtual void addScaledDampingForce(btScalar scale, TVStack& force)
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{
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int numNodes = getNumNodes();
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btAssert(numNodes <= force.size())
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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const btSoftBody* psb = m_softBodies[i];
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for (int j = 0; j < psb->m_links.size(); ++j)
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{
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const btSoftBody::Link& link = psb->m_links[j];
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btSoftBody::Node* node1 = link.m_n[0];
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btSoftBody::Node* node2 = link.m_n[1];
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size_t id1 = node1->index;
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size_t id2 = node2->index;
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// damping force
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btVector3 v_diff = (node2->m_v - node1->m_v);
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btScalar k_damp = psb->m_dampingCoefficient;
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btVector3 scaled_force = scale * v_diff * k_damp;
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force[id1] += scaled_force;
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force[id2] -= scaled_force;
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}
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}
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}
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virtual void addScaledElasticForce(btScalar scale, TVStack& force)
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{
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int numNodes = getNumNodes();
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btAssert(numNodes <= force.size())
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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const btSoftBody* psb = m_softBodies[i];
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for (int j = 0; j < psb->m_links.size(); ++j)
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{
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const btSoftBody::Link& link = psb->m_links[j];
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btSoftBody::Node* node1 = link.m_n[0];
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btSoftBody::Node* node2 = link.m_n[1];
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btScalar kLST = link.Feature::m_material->m_kLST;
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btScalar r = link.m_rl;
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size_t id1 = node1->index;
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size_t id2 = node2->index;
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// elastic force
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// explicit elastic force
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btVector3 dir = (node2->m_q - node1->m_q);
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btVector3 dir_normalized = dir.normalized();
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btVector3 scaled_force = scale * kLST * (dir - dir_normalized * r);
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force[id1] += scaled_force;
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force[id2] -= scaled_force;
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}
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}
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}
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virtual void addScaledForceDifferential(btScalar scale, const TVStack& dv, TVStack& df)
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{
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// implicit damping force differential
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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const btSoftBody* psb = m_softBodies[i];
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btScalar scaled_k_damp = psb->m_dampingCoefficient * scale;
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for (int j = 0; j < psb->m_links.size(); ++j)
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{
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const btSoftBody::Link& link = psb->m_links[j];
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btSoftBody::Node* node1 = link.m_n[0];
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btSoftBody::Node* node2 = link.m_n[1];
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size_t id1 = node1->index;
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size_t id2 = node2->index;
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btVector3 local_scaled_df = scaled_k_damp * (dv[id2] - dv[id1]);
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df[id1] += local_scaled_df;
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df[id2] -= local_scaled_df;
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}
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}
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}
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virtual btDeformableLagrangianForceType getForceType()
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{
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return BT_MASSSPRING_FORCE;
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}
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};
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#endif /* btMassSpring_h */
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