150 lines
5.3 KiB
C++
150 lines
5.3 KiB
C++
/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2003-2006 Erwin Coumans https://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_JACOBIAN_ENTRY_H
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#define BT_JACOBIAN_ENTRY_H
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#include "LinearMath/btMatrix3x3.h"
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//notes:
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// Another memory optimization would be to store m_1MinvJt in the remaining 3 w components
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// which makes the btJacobianEntry memory layout 16 bytes
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// if you only are interested in angular part, just feed massInvA and massInvB zero
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/// Jacobian entry is an abstraction that allows to describe constraints
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/// it can be used in combination with a constraint solver
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/// Can be used to relate the effect of an impulse to the constraint error
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ATTRIBUTE_ALIGNED16(class)
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btJacobianEntry
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{
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public:
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btJacobianEntry(){};
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//constraint between two different rigidbodies
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btJacobianEntry(
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const btMatrix3x3& world2A,
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const btMatrix3x3& world2B,
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const btVector3& rel_pos1, const btVector3& rel_pos2,
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const btVector3& jointAxis,
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const btVector3& inertiaInvA,
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const btScalar massInvA,
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const btVector3& inertiaInvB,
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const btScalar massInvB)
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: m_linearJointAxis(jointAxis)
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{
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m_aJ = world2A * (rel_pos1.cross(m_linearJointAxis));
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m_bJ = world2B * (rel_pos2.cross(-m_linearJointAxis));
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m_0MinvJt = inertiaInvA * m_aJ;
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m_1MinvJt = inertiaInvB * m_bJ;
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m_Adiag = massInvA + m_0MinvJt.dot(m_aJ) + massInvB + m_1MinvJt.dot(m_bJ);
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btAssert(m_Adiag > btScalar(0.0));
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}
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//angular constraint between two different rigidbodies
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btJacobianEntry(const btVector3& jointAxis,
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const btMatrix3x3& world2A,
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const btMatrix3x3& world2B,
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const btVector3& inertiaInvA,
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const btVector3& inertiaInvB)
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: m_linearJointAxis(btVector3(btScalar(0.), btScalar(0.), btScalar(0.)))
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{
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m_aJ = world2A * jointAxis;
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m_bJ = world2B * -jointAxis;
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m_0MinvJt = inertiaInvA * m_aJ;
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m_1MinvJt = inertiaInvB * m_bJ;
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m_Adiag = m_0MinvJt.dot(m_aJ) + m_1MinvJt.dot(m_bJ);
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btAssert(m_Adiag > btScalar(0.0));
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}
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//angular constraint between two different rigidbodies
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btJacobianEntry(const btVector3& axisInA,
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const btVector3& axisInB,
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const btVector3& inertiaInvA,
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const btVector3& inertiaInvB)
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: m_linearJointAxis(btVector3(btScalar(0.), btScalar(0.), btScalar(0.))), m_aJ(axisInA), m_bJ(-axisInB)
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{
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m_0MinvJt = inertiaInvA * m_aJ;
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m_1MinvJt = inertiaInvB * m_bJ;
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m_Adiag = m_0MinvJt.dot(m_aJ) + m_1MinvJt.dot(m_bJ);
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btAssert(m_Adiag > btScalar(0.0));
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}
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//constraint on one rigidbody
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btJacobianEntry(
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const btMatrix3x3& world2A,
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const btVector3& rel_pos1, const btVector3& rel_pos2,
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const btVector3& jointAxis,
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const btVector3& inertiaInvA,
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const btScalar massInvA)
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: m_linearJointAxis(jointAxis)
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{
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m_aJ = world2A * (rel_pos1.cross(jointAxis));
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m_bJ = world2A * (rel_pos2.cross(-jointAxis));
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m_0MinvJt = inertiaInvA * m_aJ;
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m_1MinvJt = btVector3(btScalar(0.), btScalar(0.), btScalar(0.));
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m_Adiag = massInvA + m_0MinvJt.dot(m_aJ);
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btAssert(m_Adiag > btScalar(0.0));
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}
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btScalar getDiagonal() const { return m_Adiag; }
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// for two constraints on the same rigidbody (for example vehicle friction)
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btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA) const
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{
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const btJacobianEntry& jacA = *this;
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btScalar lin = massInvA * jacA.m_linearJointAxis.dot(jacB.m_linearJointAxis);
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btScalar ang = jacA.m_0MinvJt.dot(jacB.m_aJ);
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return lin + ang;
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}
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// for two constraints on sharing two same rigidbodies (for example two contact points between two rigidbodies)
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btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA, const btScalar massInvB) const
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{
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const btJacobianEntry& jacA = *this;
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btVector3 lin = jacA.m_linearJointAxis * jacB.m_linearJointAxis;
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btVector3 ang0 = jacA.m_0MinvJt * jacB.m_aJ;
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btVector3 ang1 = jacA.m_1MinvJt * jacB.m_bJ;
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btVector3 lin0 = massInvA * lin;
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btVector3 lin1 = massInvB * lin;
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btVector3 sum = ang0 + ang1 + lin0 + lin1;
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return sum[0] + sum[1] + sum[2];
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}
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btScalar getRelativeVelocity(const btVector3& linvelA, const btVector3& angvelA, const btVector3& linvelB, const btVector3& angvelB)
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{
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btVector3 linrel = linvelA - linvelB;
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btVector3 angvela = angvelA * m_aJ;
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btVector3 angvelb = angvelB * m_bJ;
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linrel *= m_linearJointAxis;
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angvela += angvelb;
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angvela += linrel;
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btScalar rel_vel2 = angvela[0] + angvela[1] + angvela[2];
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return rel_vel2 + SIMD_EPSILON;
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}
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//private:
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btVector3 m_linearJointAxis;
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btVector3 m_aJ;
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btVector3 m_bJ;
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btVector3 m_0MinvJt;
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btVector3 m_1MinvJt;
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//Optimization: can be stored in the w/last component of one of the vectors
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btScalar m_Adiag;
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};
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#endif //BT_JACOBIAN_ENTRY_H
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