PxArticulationCache

Defined in include/PxArticulationReducedCoordinate.h

class PxArticulationCache

Data structure used to read and write internal articulation data.

Public Functions

inline PxArticulationCache()

void release()

Releases an articulation cache.

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.

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.

PxReal *massMatrix

The generalized mass matrix that maps joint accelerations to joint forces.

N = getDofs() * getDofs().
The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.

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 *jointSolverForces

Solver constraint joint DOF forces.

N = getDofs().
Read using PxArticulationCacheFlag::eJOINT_SOLVER_FORCES.
The indexing follows the internal DOF index order, see PxArticulationCache::jointVelocity.
Raise PxArticulationFlag::eCOMPUTE_JOINT_FORCES to enable reading the solver forces.

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.

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.

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

PxSpatialForce *sensorForces

Link sensor spatial forces.

N = getNbSensors().
Read using PxArticulationCacheFlag::eSENSOR_FORCES.
For indexing, see PxArticulationSensor::getIndex.

See also

PxArticulationSensor

PxReal *coefficientMatrix

Constraint coefficient matrix.

N = getCoefficentMatrixSize().
The user needs to allocate memory and set this member to the allocated memory.

PxReal *lambda

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

N = getNbLoopJoints().
The user needs to allocate memory and set this member to the allocated memory.

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.