105 lines
3 KiB
C++
105 lines
3 KiB
C++
/*
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Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2019 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_DEFORMABLE_GRAVITY_FORCE_H
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#define BT_DEFORMABLE_GRAVITY_FORCE_H
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#include "btDeformableLagrangianForce.h"
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class btDeformableGravityForce : public btDeformableLagrangianForce
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{
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public:
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typedef btAlignedObjectArray<btVector3> TVStack;
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btVector3 m_gravity;
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btDeformableGravityForce(const btVector3& g) : m_gravity(g)
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{
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}
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virtual void addScaledForces(btScalar scale, TVStack& force)
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{
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addScaledGravityForce(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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addScaledGravityForce(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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}
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virtual void addScaledElasticForceDifferential(btScalar scale, const TVStack& dx, TVStack& df)
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{
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}
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virtual void addScaledDampingForceDifferential(btScalar scale, const TVStack& dv, TVStack& df)
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{
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}
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virtual void buildDampingForceDifferentialDiagonal(btScalar scale, TVStack& diagA) {}
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virtual void addScaledGravityForce(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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btSoftBody* psb = m_softBodies[i];
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if (!psb->isActive())
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{
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continue;
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}
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for (int j = 0; j < psb->m_nodes.size(); ++j)
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{
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btSoftBody::Node& n = psb->m_nodes[j];
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size_t id = n.index;
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btScalar mass = (n.m_im == 0) ? 0 : 1. / n.m_im;
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btVector3 scaled_force = scale * m_gravity * mass * m_softBodies[i]->m_gravityFactor;
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force[id] += scaled_force;
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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_GRAVITY_FORCE;
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}
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// the gravitational potential energy
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virtual double totalEnergy(btScalar dt)
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{
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double e = 0;
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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btSoftBody* psb = m_softBodies[i];
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if (!psb->isActive())
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{
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continue;
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}
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for (int j = 0; j < psb->m_nodes.size(); ++j)
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{
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const btSoftBody::Node& node = psb->m_nodes[j];
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if (node.m_im > 0)
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{
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e -= m_gravity.dot(node.m_q) / node.m_im;
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}
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}
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}
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return e;
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}
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};
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#endif /* BT_DEFORMABLE_GRAVITY_FORCE_H */
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