/* | |
Bullet Continuous Collision Detection and Physics Library, http://bulletphysics.org | |
Copyright (C) 2006, 2007 Sony Computer Entertainment Inc. | |
This software is provided 'as-is', without any express or implied warranty. | |
In no event will the authors be held liable for any damages arising from the use of this software. | |
Permission is granted to anyone to use this software for any purpose, | |
including commercial applications, and to alter it and redistribute it freely, | |
subject to the following restrictions: | |
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. | |
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. | |
3. This notice may not be removed or altered from any source distribution. | |
*/ | |
#include "BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.h" | |
#include "BulletDynamics/Dynamics/btRigidBody.h" | |
#include "LinearMath/btTransformUtil.h" | |
btGeneric6DofSpringConstraint::btGeneric6DofSpringConstraint(btRigidBody& rbA, btRigidBody& rbB, const btTransform& frameInA, const btTransform& frameInB ,bool useLinearReferenceFrameA) | |
: btGeneric6DofConstraint(rbA, rbB, frameInA, frameInB, useLinearReferenceFrameA) | |
{ | |
for(int i = 0; i < 6; i++) | |
{ | |
m_springEnabled[i] = false; | |
m_equilibriumPoint[i] = btScalar(0.f); | |
m_springStiffness[i] = btScalar(0.f); | |
m_springDamping[i] = btScalar(1.f); | |
} | |
} | |
void btGeneric6DofSpringConstraint::enableSpring(int index, bool onOff) | |
{ | |
btAssert((index >= 0) && (index < 6)); | |
m_springEnabled[index] = onOff; | |
if(index < 3) | |
{ | |
m_linearLimits.m_enableMotor[index] = onOff; | |
} | |
else | |
{ | |
m_angularLimits[index - 3].m_enableMotor = onOff; | |
} | |
} | |
void btGeneric6DofSpringConstraint::setStiffness(int index, btScalar stiffness) | |
{ | |
btAssert((index >= 0) && (index < 6)); | |
m_springStiffness[index] = stiffness; | |
} | |
void btGeneric6DofSpringConstraint::setDamping(int index, btScalar damping) | |
{ | |
btAssert((index >= 0) && (index < 6)); | |
m_springDamping[index] = damping; | |
} | |
void btGeneric6DofSpringConstraint::setEquilibriumPoint() | |
{ | |
calculateTransforms(); | |
for(int i = 0; i < 3; i++) | |
{ | |
m_equilibriumPoint[i] = m_calculatedLinearDiff[i]; | |
} | |
for(int i = 0; i < 3; i++) | |
{ | |
m_equilibriumPoint[i + 3] = m_calculatedAxisAngleDiff[i]; | |
} | |
} | |
void btGeneric6DofSpringConstraint::setEquilibriumPoint(int index) | |
{ | |
btAssert((index >= 0) && (index < 6)); | |
calculateTransforms(); | |
if(index < 3) | |
{ | |
m_equilibriumPoint[index] = m_calculatedLinearDiff[index]; | |
} | |
else | |
{ | |
m_equilibriumPoint[index + 3] = m_calculatedAxisAngleDiff[index]; | |
} | |
} | |
void btGeneric6DofSpringConstraint::internalUpdateSprings(btConstraintInfo2* info) | |
{ | |
// it is assumed that calculateTransforms() have been called before this call | |
int i; | |
btVector3 relVel = m_rbB.getLinearVelocity() - m_rbA.getLinearVelocity(); | |
for(i = 0; i < 3; i++) | |
{ | |
if(m_springEnabled[i]) | |
{ | |
// get current position of constraint | |
btScalar currPos = m_calculatedLinearDiff[i]; | |
// calculate difference | |
btScalar delta = currPos - m_equilibriumPoint[i]; | |
// spring force is (delta * m_stiffness) according to Hooke's Law | |
btScalar force = delta * m_springStiffness[i]; | |
btScalar velFactor = info->fps * m_springDamping[i] / btScalar(info->m_numIterations); | |
m_linearLimits.m_targetVelocity[i] = velFactor * force; | |
m_linearLimits.m_maxMotorForce[i] = btFabs(force) / info->fps; | |
} | |
} | |
for(i = 0; i < 3; i++) | |
{ | |
if(m_springEnabled[i + 3]) | |
{ | |
// get current position of constraint | |
btScalar currPos = m_calculatedAxisAngleDiff[i]; | |
// calculate difference | |
btScalar delta = currPos - m_equilibriumPoint[i+3]; | |
// spring force is (-delta * m_stiffness) according to Hooke's Law | |
btScalar force = -delta * m_springStiffness[i+3]; | |
btScalar velFactor = info->fps * m_springDamping[i+3] / btScalar(info->m_numIterations); | |
m_angularLimits[i].m_targetVelocity = velFactor * force; | |
m_angularLimits[i].m_maxMotorForce = btFabs(force) / info->fps; | |
} | |
} | |
} | |
void btGeneric6DofSpringConstraint::getInfo2(btConstraintInfo2* info) | |
{ | |
// this will be called by constraint solver at the constraint setup stage | |
// set current motor parameters | |
internalUpdateSprings(info); | |
// do the rest of job for constraint setup | |
btGeneric6DofConstraint::getInfo2(info); | |
} | |