PxArticulationCache

Defined in include/PxArticulationReducedCoordinate.h

class PxArticulationCache

Data structure used to read and write internal articulation data.

See also

PxArticulationCacheFlag, PxArticulationReducedCoordinate::createCache, PxArticulationReducedCoordinate::applyCache, PxArticulationReducedCoordinate::copyInternalStateToCache

Public Functions

inline PxArticulationCache()
void release()

Releases an articulation cache.

See also

PxArticulationReducedCoordinate::createCache, PxArticulationReducedCoordinate::applyCache, PxArticulationReducedCoordinate::copyInternalStateToCache

Public Members

PxSpatialForce *externalForces

External forces acting on the articulation links for inverse dynamics computation.

  • N = getNbLinks().

  • Indexing follows the low-level link indices, see PxArticulationLink::getLinkIndex.

  • The forces are with respect to the center of mass of the link.

  • This field cannot be used to apply forces to links during the next PxScene::simulate() call. Use PxRigidBody::addForce and related functions instead.

See also

PxArticulationReducedCoordinate::computeGeneralizedExternalForce

PxReal *denseJacobian

Dense Jacobian data.

  • N = nbRows * nbCols = (6 * getNbLinks()) * (6 + getDofs()) -> size includes possible floating-base DOFs regardless of PxArticulationFlag::eFIX_BASE flag.

  • The links, i.e. rows are in order of the low-level link indices (minus one if PxArticulationFlag::eFIX_BASE is true), see PxArticulationLink::getLinkIndex. The corresponding spatial velocities are stacked [vx; vy; vz; wx; wy; wz], where vx and wx refer to the linear and rotational velocity in world X.

  • The DOFs, i.e. column indices correspond to the low-level DOF indices, see PxArticulationCache::jointVelocity.

See also

PxArticulationReducedCoordinate::computeDenseJacobian

PxReal *massMatrix

The generalized mass matrix used in inverse dynamics algorithms.

  • N = (getDofs() + 6) * (getDofs() + 6) -> size includes possible floating-base DOFs regardless of PxArticulationFlag::eFIX_BASE flag.

  • If PxArticulationFlag::eFIX_BASE is true, the terms corresponding to the root DoFs are included in the top left block of the matrix. For these terms, column indices correspond to linear acceleration first then angular acceleration, row indices correspond to force first then torque. The bottom right block of the matrix corresponds to the joint DoFs terms, column indices correspond to joint acceleration, row indices correspond to joint force.

  • If PxArticulationFlag::eFIX_BASE is false, only the terms corresponding to the joint DoFs are included, column indices correspond to joint acceleration, row indices correspond to joint force.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

  • The mass matrix is indexed [nCols * row + column].

See also

PxArticulationReducedCoordinate::computeMassMatrix, PxArticulationReducedCoordinate::computeGeneralizedMassMatrix

PxReal *coriolisForce

The Coriolis and centrifugal compensation forces used in inverse dynamics algorithms.

  • N = getDofs() + 6 -> size includes possible floating-base DOFs regardless of PxArticulationFlag::eFIX_BASE flag.

  • If PxArticulationFlag::eFIX_BASE is true, the terms corresponding to the root DoFs are included at the start of the array (force then torque), followed by the joint DoFs terms.

  • If PxArticulationFlag::eFIX_BASE is false, only the terms corresponding to the joint DoFs are included.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

See also

PxArticulationReducedCoordinate::computeCoriolisCompensation

PxReal *gravityCompensationForce

The gravity compensation forces used in inverse dynamics algorithms.

  • N = getDofs() + 6 -> size includes possible floating-base DOFs regardless of PxArticulationFlag::eFIX_BASE flag.

  • If PxArticulationFlag::eFIX_BASE is true, the terms corresponding to the root DoFs are included at the start of the array (force then torque), followed by the joint DoFs terms.

  • If PxArticulationFlag::eFIX_BASE is false, only the terms corresponding to the joint DoFs are included.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

See also

PxArticulationReducedCoordinate::computeGravityCompensation

PxReal *centroidalMomentumMatrix

The centroidal momentum matrix that maps velocities to centroidal momentum.

  • N = 6 * (getDofs() + 6).

  • Each row includes first the term related to the DOF of the root (linear, then angular), then the joint DOF following the internal DOF index order, see PxArticulationCache::jointVelocity.

  • The centroidal momentum includes first the linear and then the angular contribution.

See also

PxArticulationReducedCoordinate::computeCentroidalMomentumMatrix

PxReal *centroidalMomentumBias

The centroidal momentum bias force.

This is a second-order term to calculate the derivative of the centroidal momentum.

  • N = 6.

  • The centroidal momentum includes first the linear and then the angular contribution.

See also

PxArticulationReducedCoordinate::computeCentroidalMomentumMatrix

PxReal *jointVelocity

The articulation joint DOF velocities.

  • N = getDofs().

  • Read/write using PxArticulationCacheFlag::eVELOCITY.

  • The indexing follows the internal DOF index order. Therefore, the application should calculate the DOF data indices by summing the joint DOFs in the order of the links’ low-level indices (see the manual Section “Cache Indexing” for a snippet for this calculation): 

    Low-level link index:   | link 0 | link 1 | link 2 | link 3 | ... | <- PxArticulationLink::getLinkIndex()

    Link inbound joint DOF: | 0      | 1      | 2      | 1      | ... | <- PxArticulationLink::getInboundJointDof()

    Low-level DOF index:    | -      | 0      | 1, 2   | 3      | ... |
    The root link always has low-level index 0 and always has zero inbound joint DOFs. The link DOF indexing follows the order in PxArticulationAxis::Enum. For example, assume that low-level link 2 has an inbound spherical joint with two DOFs: eSWING1 and eSWING2. The corresponding low-level joint DOF indices are therefore 1 for eSWING1 and 2 for eSWING2.

PxReal *jointAcceleration

The articulation joint DOF accelerations.

  • N = getDofs().

  • Read using PxArticulationCacheFlag::eACCELERATION.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

  • Delta joint DOF velocities can be computed from acceleration * dt.

PxReal *jointPosition

The articulation joint DOF positions.

  • N = getDofs().

  • Read/write using PxArticulationCacheFlag::ePOSITION.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

  • For spherical joints, the joint position for each axis on the joint must be in range [-Pi, Pi].

PxReal *jointForce

The articulation joint DOF forces.

  • N = getDofs().

  • Read/Write using PxArticulationCacheFlag::eFORCE.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

  • Applied joint forces persist and are applied each frame until changed.

PxReal *jointTargetPositions

The articulation joint drive target positions.

  • N = getDofs().

  • Write using PxArticulationCacheFlag::eJOINT_TARGET_POSITIONS.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

PxReal *jointTargetVelocities

The articulation joint drive target velocities.

  • N = getDofs().

  • Write using PxArticulationCacheFlag::eJOINT_TARGET_VELOCITIES.

  • The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

PxSpatialVelocity *linkVelocity

Link spatial velocity.

  • N = getNbLinks().

  • Read using PxArticulationCacheFlag::eLINK_VELOCITY.

  • The indexing follows the internal link indexing, see PxArticulationLink::getLinkIndex.

  • The velocity is with respect to the link’s center of mass but represented in world space.

See also

PxRigidBody::getCMassLocalPose

PxSpatialVelocity *linkAcceleration

Link classical acceleration.

  • N = getNbLinks().

  • Read using PxArticulationCacheFlag::eLINK_ACCELERATION.

  • The indexing follows the internal link indexing, see PxArticulationLink::getLinkIndex.

  • The acceleration is with respect to the link’s center of mass.

See also

PxArticulationReducedCoordinate::getLinkAcceleration, PxRigidBody::getCMassLocalPose

PxSpatialForce *linkIncomingJointForce

Link incoming joint force, i.e.

the total force transmitted from the parent link to this link.

  • N = getNbLinks().

  • Read using PxArticulationCacheFlag::eLINK_INCOMING_JOINT_FORCE.

  • The indexing follows the internal link indexing, see PxArticulationLink::getLinkIndex.

  • The force is reported in the child joint frame of the link’s incoming joint.

See also

PxArticulationJointReducedCoordinate::getChildPose

Note

The root link reports a zero spatial force.

PxVec3 *linkForce

Link force, i.e.

an external force applied to the link’s center of mass.

  • N = getNbLinks().

  • Write using PxArticulationCacheFlag::eLINK_FORCE.

  • The indexing follows the internal link indexing, see PxArticulationLink::getLinkIndex.

  • The force is given in world space.

PxVec3 *linkTorque

Link torque, i.e.

an external torque applied to the link.

  • N = getNbLinks().

  • Write using PxArticulationCacheFlag::eLINK_TORQUE.

  • The indexing follows the internal link indexing, see PxArticulationLink::getLinkIndex.

  • The torque is given in world space.

PxArticulationRootLinkData *rootLinkData

Root link transform, velocities, and accelerations.

  • N = 1.

  • Read/write using PxArticulationCacheFlag::eROOT_TRANSFORM and PxArticulationCacheFlag::eROOT_VELOCITIES (accelerations are read-only).

See also

PxArticulationRootLinkData

PxReal *coefficientMatrix

Constraint coefficient matrix.

Deprecated:

The API related to loop joints will be removed in a future version once a replacement is made available.

  • N = getCoefficentMatrixSize().

  • The user needs to allocate memory and set this member to the allocated memory.

See also

PxArticulationReducedCoordinate::computeCoefficientMatrix

PxReal *lambda

Constraint lambda values (impulses applied by the respective constraints).

Deprecated:

The API related to loop joints will be removed in a future version once a replacement is made available.

  • N = getNbLoopJoints().

  • The user needs to allocate memory and set this member to the allocated memory.

See also

PxArticulationReducedCoordinate::computeLambda

void *scratchMemory

The scratch memory is used for internal calculations.

void *scratchAllocator

The scratch allocator is used for internal calculations.

PxU32 version

The cache version used internally to check compatibility with the articulation, i.e. detect if the articulation configuration changed after the cache was created.