1 files changed, 185 insertions, 0 deletions
diff --git a/thirdparty/bullet/src/BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.cpp b/thirdparty/bullet/src/BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.cpp
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+++ b/thirdparty/bullet/src/BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.cpp
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+/*
+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 "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)
+{
+    init();
+}
+
+
+btGeneric6DofSpringConstraint::btGeneric6DofSpringConstraint(btRigidBody& rbB, const btTransform& frameInB, bool useLinearReferenceFrameB)
+        : btGeneric6DofConstraint(rbB, frameInB, useLinearReferenceFrameB)
+{
+    init();
+}
+
+
+void btGeneric6DofSpringConstraint::init()
+{
+	m_objectType = D6_SPRING_CONSTRAINT_TYPE;
+
+	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();
+	int i;
+
+	for( i = 0; i < 3; i++)
+	{
+		m_equilibriumPoint[i] = m_calculatedLinearDiff[i];
+	}
+	for(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] = m_calculatedAxisAngleDiff[index - 3];
+	}
+}
+
+void btGeneric6DofSpringConstraint::setEquilibriumPoint(int index, btScalar val)
+{
+	btAssert((index >= 0) && (index < 6));
+	m_equilibriumPoint[index] = val;
+}
+
+
+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);
+}
+
+
+void btGeneric6DofSpringConstraint::setAxis(const btVector3& axis1,const btVector3& axis2)
+{
+	btVector3 zAxis = axis1.normalized();
+	btVector3 yAxis = axis2.normalized();
+	btVector3 xAxis = yAxis.cross(zAxis); // we want right coordinate system
+
+	btTransform frameInW;
+	frameInW.setIdentity();
+	frameInW.getBasis().setValue(	xAxis[0], yAxis[0], zAxis[0],	
+                                xAxis[1], yAxis[1], zAxis[1],
+                                xAxis[2], yAxis[2], zAxis[2]);
+
+	// now get constraint frame in local coordinate systems
+	m_frameInA = m_rbA.getCenterOfMassTransform().inverse() * frameInW;
+	m_frameInB = m_rbB.getCenterOfMassTransform().inverse() * frameInW;
+
+  calculateTransforms();
+}
+
+
+