2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2013 Erwin Coumans http://bulletphysics.org
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:
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.
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16 #ifndef BT_MULTIBODY_LINK_H
17 #define BT_MULTIBODY_LINK_H
19 #include "LinearMath/btQuaternion.h"
20 #include "LinearMath/btVector3.h"
21 #include "BulletCollision/CollisionDispatch/btCollisionObject.h"
23 enum btMultiBodyLinkFlags
25 BT_MULTIBODYLINKFLAGS_DISABLE_PARENT_COLLISION = 1,
26 BT_MULTIBODYLINKFLAGS_DISABLE_ALL_PARENT_COLLISION = 2,
29 //both defines are now permanently enabled
30 #define BT_MULTIBODYLINK_INCLUDE_PLANAR_JOINTS
31 #define TEST_SPATIAL_ALGEBRA_LAYER
34 // Various spatial helper functions
39 #include "LinearMath/btSpatialAlgebra.h"
47 struct btMultibodyLink
49 BT_DECLARE_ALIGNED_ALLOCATOR();
51 btScalar m_mass; // mass of link
52 btVector3 m_inertiaLocal; // inertia of link (local frame; diagonal)
54 int m_parent; // index of the parent link (assumed to be < index of this link), or -1 if parent is the base link.
56 btQuaternion m_zeroRotParentToThis; // rotates vectors in parent-frame to vectors in local-frame (when q=0). constant.
58 btVector3 m_dVector; // vector from the inboard joint pos to this link's COM. (local frame.) constant.
59 //this is set to zero for planar joint (see also m_eVector comment)
61 // m_eVector is constant, but depends on the joint type:
62 // revolute, fixed, prismatic, spherical: vector from parent's COM to the pivot point, in PARENT's frame.
63 // planar: vector from COM of parent to COM of this link, WHEN Q = 0. (local frame.)
64 // todo: fix the planar so it is consistent with the other joints
68 btSpatialMotionVector m_absFrameTotVelocity, m_absFrameLocVelocity;
70 enum eFeatherstoneJointType
80 // "axis" = spatial joint axis (Mirtich Defn 9 p104). (expressed in local frame.) constant.
81 // for prismatic: m_axesTop[0] = zero;
82 // m_axesBottom[0] = unit vector along the joint axis.
83 // for revolute: m_axesTop[0] = unit vector along the rotation axis (u);
84 // m_axesBottom[0] = u cross m_dVector (i.e. COM linear motion due to the rotation at the joint)
86 // for spherical: m_axesTop[0][1][2] (u1,u2,u3) form a 3x3 identity matrix (3 rotation axes)
87 // m_axesBottom[0][1][2] cross u1,u2,u3 (i.e. COM linear motion due to the rotation at the joint)
89 // for planar: m_axesTop[0] = unit vector along the rotation axis (u); defines the plane of motion
90 // m_axesTop[1][2] = zero
91 // m_axesBottom[0] = zero
92 // m_axesBottom[1][2] = unit vectors along the translational axes on that plane
93 btSpatialMotionVector m_axes[6];
94 void setAxisTop(int dof, const btVector3 &axis) { m_axes[dof].m_topVec = axis; }
95 void setAxisBottom(int dof, const btVector3 &axis)
97 m_axes[dof].m_bottomVec = axis;
99 void setAxisTop(int dof, const btScalar &x, const btScalar &y, const btScalar &z)
101 m_axes[dof].m_topVec.setValue(x, y, z);
103 void setAxisBottom(int dof, const btScalar &x, const btScalar &y, const btScalar &z)
105 m_axes[dof].m_bottomVec.setValue(x, y, z);
107 const btVector3 &getAxisTop(int dof) const { return m_axes[dof].m_topVec; }
108 const btVector3 &getAxisBottom(int dof) const { return m_axes[dof].m_bottomVec; }
110 int m_dofOffset, m_cfgOffset;
112 btQuaternion m_cachedRotParentToThis; // rotates vectors in parent frame to vectors in local frame
113 btVector3 m_cachedRVector; // vector from COM of parent to COM of this link, in local frame.
115 // predicted verstion
116 btQuaternion m_cachedRotParentToThis_interpolate; // rotates vectors in parent frame to vectors in local frame
117 btVector3 m_cachedRVector_interpolate; // vector from COM of parent to COM of this link, in local frame.
119 btVector3 m_appliedForce; // In WORLD frame
120 btVector3 m_appliedTorque; // In WORLD frame
122 btVector3 m_appliedConstraintForce; // In WORLD frame
123 btVector3 m_appliedConstraintTorque; // In WORLD frame
125 btScalar m_jointPos[7];
126 btScalar m_jointPos_interpolate[7];
128 //m_jointTorque is the joint torque applied by the user using 'addJointTorque'.
129 //It gets set to zero after each internal stepSimulation call
130 btScalar m_jointTorque[6];
132 class btMultiBodyLinkCollider *m_collider;
135 int m_dofCount, m_posVarCount; //redundant but handy
137 eFeatherstoneJointType m_jointType;
139 struct btMultiBodyJointFeedback *m_jointFeedback;
141 btTransform m_cachedWorldTransform; //this cache is updated when calling btMultiBody::forwardKinematics
143 const char *m_linkName; //m_linkName memory needs to be managed by the developer/user!
144 const char *m_jointName; //m_jointName memory needs to be managed by the developer/user!
145 const void *m_userPtr; //m_userPtr ptr needs to be managed by the developer/user!
147 btScalar m_jointDamping; //todo: implement this internally. It is unused for now, it is set by a URDF loader. User can apply manual damping.
148 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.
149 btScalar m_jointLowerLimit; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
150 btScalar m_jointUpperLimit; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
151 btScalar m_jointMaxForce; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
152 btScalar m_jointMaxVelocity; //todo: implement this internally. It is unused for now, it is set by a URDF loader.
154 // ctor: set some sensible defaults
158 m_zeroRotParentToThis(0, 0, 0, 1),
159 m_cachedRotParentToThis(0, 0, 0, 1),
160 m_cachedRotParentToThis_interpolate(0, 0, 0, 1),
165 m_jointType(btMultibodyLink::eInvalid),
172 m_jointLowerLimit(0),
173 m_jointUpperLimit(0),
175 m_jointMaxVelocity(0)
177 m_inertiaLocal.setValue(1, 1, 1);
178 setAxisTop(0, 0., 0., 0.);
179 setAxisBottom(0, 1., 0., 0.);
180 m_dVector.setValue(0, 0, 0);
181 m_eVector.setValue(0, 0, 0);
182 m_cachedRVector.setValue(0, 0, 0);
183 m_cachedRVector_interpolate.setValue(0, 0, 0);
184 m_appliedForce.setValue(0, 0, 0);
185 m_appliedTorque.setValue(0, 0, 0);
186 m_appliedConstraintForce.setValue(0, 0, 0);
187 m_appliedConstraintTorque.setValue(0, 0, 0);
189 m_jointPos[0] = m_jointPos[1] = m_jointPos[2] = m_jointPos[4] = m_jointPos[5] = m_jointPos[6] = 0.f;
190 m_jointPos[3] = 1.f; //"quat.w"
191 m_jointTorque[0] = m_jointTorque[1] = m_jointTorque[2] = m_jointTorque[3] = m_jointTorque[4] = m_jointTorque[5] = 0.f;
192 m_cachedWorldTransform.setIdentity();
195 // routine to update m_cachedRotParentToThis and m_cachedRVector
196 void updateCacheMultiDof(btScalar *pq = 0)
198 btScalar *pJointPos = (pq ? pq : &m_jointPos[0]);
199 btQuaternion& cachedRot = m_cachedRotParentToThis;
200 btVector3& cachedVector = m_cachedRVector;
205 cachedRot = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
206 cachedVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector);
212 // m_cachedRotParentToThis never changes, so no need to update
213 cachedVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector) + pJointPos[0] * getAxisBottom(0);
219 cachedRot = btQuaternion(pJointPos[0], pJointPos[1], pJointPos[2], -pJointPos[3]) * m_zeroRotParentToThis;
220 cachedVector = m_dVector + quatRotate(cachedRot, m_eVector);
226 cachedRot = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
227 cachedVector = quatRotate(btQuaternion(getAxisTop(0), -pJointPos[0]), pJointPos[1] * getAxisBottom(1) + pJointPos[2] * getAxisBottom(2)) + quatRotate(cachedRot, m_eVector);
233 cachedRot = m_zeroRotParentToThis;
234 cachedVector = m_dVector + quatRotate(cachedRot, m_eVector);
244 m_cachedRotParentToThis_interpolate = m_cachedRotParentToThis;
245 m_cachedRVector_interpolate = m_cachedRVector;
248 void updateInterpolationCacheMultiDof()
250 btScalar *pJointPos = &m_jointPos_interpolate[0];
252 btQuaternion& cachedRot = m_cachedRotParentToThis_interpolate;
253 btVector3& cachedVector = m_cachedRVector_interpolate;
258 cachedRot = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
259 cachedVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector);
265 // m_cachedRotParentToThis never changes, so no need to update
266 cachedVector = m_dVector + quatRotate(m_cachedRotParentToThis, m_eVector) + pJointPos[0] * getAxisBottom(0);
272 cachedRot = btQuaternion(pJointPos[0], pJointPos[1], pJointPos[2], -pJointPos[3]) * m_zeroRotParentToThis;
273 cachedVector = m_dVector + quatRotate(cachedRot, m_eVector);
279 cachedRot = btQuaternion(getAxisTop(0), -pJointPos[0]) * m_zeroRotParentToThis;
280 cachedVector = quatRotate(btQuaternion(getAxisTop(0), -pJointPos[0]), pJointPos[1] * getAxisBottom(1) + pJointPos[2] * getAxisBottom(2)) + quatRotate(cachedRot, m_eVector);
286 cachedRot = m_zeroRotParentToThis;
287 cachedVector = m_dVector + quatRotate(cachedRot, m_eVector);
303 #endif //BT_MULTIBODY_LINK_H