240 lines
8.6 KiB
C++
240 lines
8.6 KiB
C++
/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2013 Erwin Coumans 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_MULTIBODY_LINK_H
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#define BT_MULTIBODY_LINK_H
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#include "LinearMath/btQuaternion.h"
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#include "LinearMath/btVector3.h"
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#include "BulletCollision/CollisionDispatch/btCollisionObject.h"
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enum btMultiBodyLinkFlags
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{
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BT_MULTIBODYLINKFLAGS_DISABLE_PARENT_COLLISION = 1,
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BT_MULTIBODYLINKFLAGS_DISABLE_ALL_PARENT_COLLISION = 2,
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};
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//both defines are now permanently enabled
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#define BT_MULTIBODYLINK_INCLUDE_PLANAR_JOINTS
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#define TEST_SPATIAL_ALGEBRA_LAYER
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//
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// Various spatial helper functions
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//
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//namespace {
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#include "LinearMath/btSpatialAlgebra.h"
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//}
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//
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// Link struct
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//
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struct btMultibodyLink
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{
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BT_DECLARE_ALIGNED_ALLOCATOR();
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btScalar m_mass; // mass of link
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btVector3 m_inertiaLocal; // inertia of link (local frame; diagonal)
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int m_parent; // index of the parent link (assumed to be < index of this link), or -1 if parent is the base link.
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btQuaternion m_zeroRotParentToThis; // rotates vectors in parent-frame to vectors in local-frame (when q=0). constant.
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btVector3 m_dVector; // vector from the inboard joint pos to this link's COM. (local frame.) constant.
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//this is set to zero for planar joint (see also m_eVector comment)
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// m_eVector is constant, but depends on the joint type:
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// revolute, fixed, prismatic, spherical: vector from parent's COM to the pivot point, in PARENT's frame.
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// planar: vector from COM of parent to COM of this link, WHEN Q = 0. (local frame.)
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// todo: fix the planar so it is consistent with the other joints
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btVector3 m_eVector;
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btSpatialMotionVector m_absFrameTotVelocity, m_absFrameLocVelocity;
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enum eFeatherstoneJointType
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{
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eRevolute = 0,
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ePrismatic = 1,
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eSpherical = 2,
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ePlanar = 3,
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eFixed = 4,
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eInvalid
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};
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// "axis" = spatial joint axis (Mirtich Defn 9 p104). (expressed in local frame.) constant.
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// for prismatic: m_axesTop[0] = zero;
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// m_axesBottom[0] = unit vector along the joint axis.
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// for revolute: m_axesTop[0] = unit vector along the rotation axis (u);
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// m_axesBottom[0] = u cross m_dVector (i.e. COM linear motion due to the rotation at the joint)
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//
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// for spherical: m_axesTop[0][1][2] (u1,u2,u3) form a 3x3 identity matrix (3 rotation axes)
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// m_axesBottom[0][1][2] cross u1,u2,u3 (i.e. COM linear motion due to the rotation at the joint)
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//
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// for planar: m_axesTop[0] = unit vector along the rotation axis (u); defines the plane of motion
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// m_axesTop[1][2] = zero
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// m_axesBottom[0] = zero
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// m_axesBottom[1][2] = unit vectors along the translational axes on that plane
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btSpatialMotionVector m_axes[6];
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void setAxisTop(int dof, const btVector3 &axis) { m_axes[dof].m_topVec = axis; }
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void setAxisBottom(int dof, const btVector3 &axis)
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{
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m_axes[dof].m_bottomVec = axis;
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}
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void setAxisTop(int dof, const btScalar &x, const btScalar &y, const btScalar &z)
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{
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m_axes[dof].m_topVec.setValue(x, y, z);
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}
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void setAxisBottom(int dof, const btScalar &x, const btScalar &y, const btScalar &z)
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{
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m_axes[dof].m_bottomVec.setValue(x, y, z);
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}
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const btVector3 &getAxisTop(int dof) const { return m_axes[dof].m_topVec; }
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const btVector3 &getAxisBottom(int dof) const { return m_axes[dof].m_bottomVec; }
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int m_dofOffset, m_cfgOffset;
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btQuaternion m_cachedRotParentToThis; // rotates vectors in parent frame to vectors in local frame
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btVector3 m_cachedRVector; // vector from COM of parent to COM of this link, in local frame.
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btVector3 m_appliedForce; // In WORLD frame
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btVector3 m_appliedTorque; // In WORLD frame
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btVector3 m_appliedConstraintForce; // In WORLD frame
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btVector3 m_appliedConstraintTorque; // In WORLD frame
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btScalar m_jointPos[7];
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//m_jointTorque is the joint torque applied by the user using 'addJointTorque'.
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//It gets set to zero after each internal stepSimulation call
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btScalar m_jointTorque[6];
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class btMultiBodyLinkCollider *m_collider;
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int m_flags;
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int m_dofCount, m_posVarCount; //redundant but handy
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eFeatherstoneJointType m_jointType;
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struct btMultiBodyJointFeedback *m_jointFeedback;
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btTransform m_cachedWorldTransform; //this cache is updated when calling btMultiBody::forwardKinematics
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const char *m_linkName; //m_linkName memory needs to be managed by the developer/user!
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const char *m_jointName; //m_jointName memory needs to be managed by the developer/user!
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const void *m_userPtr; //m_userPtr ptr needs to be managed by the developer/user!
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btScalar m_jointDamping; //todo: implement this internally. It is unused for now, it is set by a URDF loader. User can apply manual damping.
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btScalar m_jointFriction; //todo: implement this internally. It is unused for now, it is set by a URDF loader. User can apply manual friction using a velocity motor.
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btScalar m_jointLowerLimit; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
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btScalar m_jointUpperLimit; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
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btScalar m_jointMaxForce; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
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btScalar m_jointMaxVelocity; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
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// ctor: set some sensible defaults
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btMultibodyLink()
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: m_mass(1),
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m_parent(-1),
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m_zeroRotParentToThis(0, 0, 0, 1),
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m_cachedRotParentToThis(0, 0, 0, 1),
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m_collider(0),
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m_flags(0),
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m_dofCount(0),
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m_posVarCount(0),
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m_jointType(btMultibodyLink::eInvalid),
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m_jointFeedback(0),
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m_linkName(0),
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m_jointName(0),
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m_userPtr(0),
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m_jointDamping(0),
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m_jointFriction(0),
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m_jointLowerLimit(0),
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m_jointUpperLimit(0),
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m_jointMaxForce(0),
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m_jointMaxVelocity(0)
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{
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m_inertiaLocal.setValue(1, 1, 1);
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setAxisTop(0, 0., 0., 0.);
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setAxisBottom(0, 1., 0., 0.);
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m_dVector.setValue(0, 0, 0);
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m_eVector.setValue(0, 0, 0);
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m_cachedRVector.setValue(0, 0, 0);
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m_appliedForce.setValue(0, 0, 0);
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m_appliedTorque.setValue(0, 0, 0);
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m_appliedConstraintForce.setValue(0, 0, 0);
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m_appliedConstraintTorque.setValue(0, 0, 0);
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//
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m_jointPos[0] = m_jointPos[1] = m_jointPos[2] = m_jointPos[4] = m_jointPos[5] = m_jointPos[6] = 0.f;
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m_jointPos[3] = 1.f; //"quat.w"
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m_jointTorque[0] = m_jointTorque[1] = m_jointTorque[2] = m_jointTorque[3] = m_jointTorque[4] = m_jointTorque[5] = 0.f;
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m_cachedWorldTransform.setIdentity();
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}
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// routine to update m_cachedRotParentToThis and m_cachedRVector
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void updateCacheMultiDof(btScalar *pq = 0)
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{
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btScalar *pJointPos = (pq ? pq : &m_jointPos[0]);
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switch (m_jointType)
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{
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case eRevolute:
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{
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m_cachedRotParentToThis = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
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m_cachedRVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector);
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break;
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}
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case ePrismatic:
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{
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// m_cachedRotParentToThis never changes, so no need to update
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m_cachedRVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector) + pJointPos[0] * getAxisBottom(0);
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break;
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}
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case eSpherical:
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{
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m_cachedRotParentToThis = btQuaternion(pJointPos[0], pJointPos[1], pJointPos[2], -pJointPos[3]) * m_zeroRotParentToThis;
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m_cachedRVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector);
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break;
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}
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case ePlanar:
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{
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m_cachedRotParentToThis = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
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m_cachedRVector = quatRotate(btQuaternion(getAxisTop(0), -pJointPos[0]), pJointPos[1] * getAxisBottom(1) + pJointPos[2] * getAxisBottom(2)) + quatRotate(m_cachedRotParentToThis, m_eVector);
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break;
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}
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case eFixed:
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{
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m_cachedRotParentToThis = m_zeroRotParentToThis;
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m_cachedRVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector);
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break;
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}
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default:
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{
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//invalid type
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btAssert(0);
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}
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}
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}
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};
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#endif //BT_MULTIBODY_LINK_H
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