1 /* 2 Bullet Continuous Collision Detection and Physics Library, http://bulletphysics.org 3 Copyright (C) 2006, 2007 Sony Computer Entertainment Inc. 4 5 This software is provided 'as-is', without any express or implied warranty. 6 In no event will the authors be held liable for any damages arising from the use of this software. 7 Permission is granted to anyone to use this software for any purpose, 8 including commercial applications, and to alter it and redistribute it freely, 9 subject to the following restrictions: 10 11 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. 12 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. 13 3. This notice may not be removed or altered from any source distribution. 14 */ 15 16 #include "btGeneric6DofSpringConstraint.h" 17 #include "BulletDynamics/Dynamics/btRigidBody.h" 18 #include "LinearMath/btTransformUtil.h" 19 20 21 btGeneric6DofSpringConstraint::btGeneric6DofSpringConstraint(btRigidBody& rbA, btRigidBody& rbB, const btTransform& frameInA, const btTransform& frameInB ,bool useLinearReferenceFrameA) 22 : btGeneric6DofConstraint(rbA, rbB, frameInA, frameInB, useLinearReferenceFrameA) 23 { 24 init(); 25 } 26 27 28 btGeneric6DofSpringConstraint::btGeneric6DofSpringConstraint(btRigidBody& rbB, const btTransform& frameInB, bool useLinearReferenceFrameB) 29 : btGeneric6DofConstraint(rbB, frameInB, useLinearReferenceFrameB) 30 { 31 init(); 32 } 33 34 35 void btGeneric6DofSpringConstraint::init() 36 { 37 m_objectType = D6_SPRING_CONSTRAINT_TYPE; 38 39 for(int i = 0; i < 6; i++) 40 { 41 m_springEnabled[i] = false; 42 m_equilibriumPoint[i] = btScalar(0.f); 43 m_springStiffness[i] = btScalar(0.f); 44 m_springDamping[i] = btScalar(1.f); 45 } 46 } 47 48 49 void btGeneric6DofSpringConstraint::enableSpring(int index, bool onOff) 50 { 51 btAssert((index >= 0) && (index < 6)); 52 m_springEnabled[index] = onOff; 53 if(index < 3) 54 { 55 m_linearLimits.m_enableMotor[index] = onOff; 56 } 57 else 58 { 59 m_angularLimits[index - 3].m_enableMotor = onOff; 60 } 61 } 62 63 64 65 void btGeneric6DofSpringConstraint::setStiffness(int index, btScalar stiffness) 66 { 67 btAssert((index >= 0) && (index < 6)); 68 m_springStiffness[index] = stiffness; 69 } 70 71 72 void btGeneric6DofSpringConstraint::setDamping(int index, btScalar damping) 73 { 74 btAssert((index >= 0) && (index < 6)); 75 m_springDamping[index] = damping; 76 } 77 78 79 void btGeneric6DofSpringConstraint::setEquilibriumPoint() 80 { 81 calculateTransforms(); 82 int i; 83 84 for( i = 0; i < 3; i++) 85 { 86 m_equilibriumPoint[i] = m_calculatedLinearDiff[i]; 87 } 88 for(i = 0; i < 3; i++) 89 { 90 m_equilibriumPoint[i + 3] = m_calculatedAxisAngleDiff[i]; 91 } 92 } 93 94 95 96 void btGeneric6DofSpringConstraint::setEquilibriumPoint(int index) 97 { 98 btAssert((index >= 0) && (index < 6)); 99 calculateTransforms(); 100 if(index < 3) 101 { 102 m_equilibriumPoint[index] = m_calculatedLinearDiff[index]; 103 } 104 else 105 { 106 m_equilibriumPoint[index] = m_calculatedAxisAngleDiff[index - 3]; 107 } 108 } 109 110 void btGeneric6DofSpringConstraint::setEquilibriumPoint(int index, btScalar val) 111 { 112 btAssert((index >= 0) && (index < 6)); 113 m_equilibriumPoint[index] = val; 114 } 115 116 117 void btGeneric6DofSpringConstraint::internalUpdateSprings(btConstraintInfo2* info) 118 { 119 // it is assumed that calculateTransforms() have been called before this call 120 int i; 121 //btVector3 relVel = m_rbB.getLinearVelocity() - m_rbA.getLinearVelocity(); 122 for(i = 0; i < 3; i++) 123 { 124 if(m_springEnabled[i]) 125 { 126 // get current position of constraint 127 btScalar currPos = m_calculatedLinearDiff[i]; 128 // calculate difference 129 btScalar delta = currPos - m_equilibriumPoint[i]; 130 // spring force is (delta * m_stiffness) according to Hooke's Law 131 btScalar force = delta * m_springStiffness[i]; 132 btScalar velFactor = info->fps * m_springDamping[i] / btScalar(info->m_numIterations); 133 m_linearLimits.m_targetVelocity[i] = velFactor * force; 134 m_linearLimits.m_maxMotorForce[i] = btFabs(force) / info->fps; 135 } 136 } 137 for(i = 0; i < 3; i++) 138 { 139 if(m_springEnabled[i + 3]) 140 { 141 // get current position of constraint 142 btScalar currPos = m_calculatedAxisAngleDiff[i]; 143 // calculate difference 144 btScalar delta = currPos - m_equilibriumPoint[i+3]; 145 // spring force is (-delta * m_stiffness) according to Hooke's Law 146 btScalar force = -delta * m_springStiffness[i+3]; 147 btScalar velFactor = info->fps * m_springDamping[i+3] / btScalar(info->m_numIterations); 148 m_angularLimits[i].m_targetVelocity = velFactor * force; 149 m_angularLimits[i].m_maxMotorForce = btFabs(force) / info->fps; 150 } 151 } 152 } 153 154 155 void btGeneric6DofSpringConstraint::getInfo2(btConstraintInfo2* info) 156 { 157 // this will be called by constraint solver at the constraint setup stage 158 // set current motor parameters 159 internalUpdateSprings(info); 160 // do the rest of job for constraint setup 161 btGeneric6DofConstraint::getInfo2(info); 162 } 163 164 165 void btGeneric6DofSpringConstraint::setAxis(const btVector3& axis1,const btVector3& axis2) 166 { 167 btVector3 zAxis = axis1.normalized(); 168 btVector3 yAxis = axis2.normalized(); 169 btVector3 xAxis = yAxis.cross(zAxis); // we want right coordinate system 170 171 btTransform frameInW; 172 frameInW.setIdentity(); 173 frameInW.getBasis().setValue( xAxis[0], yAxis[0], zAxis[0], 174 xAxis[1], yAxis[1], zAxis[1], 175 xAxis[2], yAxis[2], zAxis[2]); 176 177 // now get constraint frame in local coordinate systems 178 m_frameInA = m_rbA.getCenterOfMassTransform().inverse() * frameInW; 179 m_frameInB = m_rbB.getCenterOfMassTransform().inverse() * frameInW; 180 181 calculateTransforms(); 182 } 183 184 185 186
