esp::physics::BulletArticulatedObject class

Base classes

class ArticulatedObject
An articulated rigid object (i.e. kinematic chain). Abstract class to be derived by physics simulator specific implementations.

Constructors, destructors, conversion operators

BulletArticulatedObject(scene::SceneNode* rootNode, assets::ResourceManager& resMgr, int objectId, std::shared_ptr<btMultiBodyDynamicsWorld> bWorld, std::shared_ptr<std::map<const btCollisionObject*, int>> collisionObjToObjIds)
~BulletArticulatedObject() override

Public functions

void initializeFromURDF(URDFImporter& u2b, const Magnum::Matrix4& worldTransform, scene::SceneNode* physicsNode) override
Initialize this ArticulatedObject from a parsed URDF stored in a URDFImporter. Creates a btMultiBody.
void constructStaticRigidBaseObject()
Construct a Static btRigidObject to act as a proxy collision object for the fixed base.
void updateNodes(bool force = false) override
update the SceneNode state to match the simulation state
auto getCurrentStateInstanceAttr() -> std::shared_ptr<metadata::attributes::SceneAOInstanceAttributes> override
Return a metadata::attributes::SceneAOInstanceAttributes reflecting the current state of this Articulated Object.
auto getRootLinearVelocity() const -> Mn::Vector3 override
Get the linear velocity of the articulated object's root in the global frame.
void setRootLinearVelocity(const Mn::Vector3& linVel) override
Set the linear velocity of the articulated object's root in the global frame.
auto getRootAngularVelocity() const -> Mn::Vector3 override
Get the angular velocity (omega) of the articulated object's root in the global frame.
void setRootAngularVelocity(const Mn::Vector3& angVel) override
Set the angular velocity (omega) of the articulated object's root in the global frame.
void setJointForces(const std::vector<float>& forces) override
Set forces/torques for all joints indexed by degrees of freedom.
void addJointForces(const std::vector<float>& forces) override
Add forces/torques to all joints indexed by degrees of freedom.
auto getJointForces() -> std::vector<float> override
Get current forces/torques for all joints indexed by degrees of freedom.
void setJointVelocities(const std::vector<float>& vels) override
Set velocities for all joints indexed by degrees of freedom.
auto getJointVelocities() -> std::vector<float> override
Get current velocities for all joints indexed by degrees of freedom.
void setJointPositions(const std::vector<float>& positions) override
Set positions for all joints.
auto getJointPositions() -> std::vector<float> override
Get positions for all joints.
auto getJointMotorTorques(double fixedTimeStep) -> std::vector<float> override
Get the torques on each joint.
auto getJointPositionLimits() -> std::pair<std::vector<float>, std::vector<float>> override
Get position limits for all joints. (lower, upper)
void addArticulatedLinkForce(int linkId, Magnum::Vector3 force) override
Add linear force to a link's COM specified in the global frame.
auto getArticulatedLinkFriction(int linkId) -> float override
Get the friction coefficient for a link.
void setArticulatedLinkFriction(int linkId, float friction) override
Set the friction coefficient for a link.
auto getLinkJointType(int linkId) const -> JointType override
Get the type of the link's parent joint.
auto getLinkDoFOffset(int linkId) const -> int override
Get the starting position for this link's parent joint in the global DoFs array.
auto getLinkNumDoFs(int linkId) const -> int override
Get the number of DoFs for this link's parent joint.
auto getLinkJointPosOffset(int linkId) const -> int override
Get the starting position for this link's parent joint in the global positions array.
auto getLinkNumJointPos(int linkId) const -> int override
Get the number of positions for this link's parent joint.
void reset() override
reset the articulated object state by clearing forces and zeroing positions and velocities.
void setActive(bool active) override
Set an object as being actively simulated or sleeping.
auto isActive() const -> bool override
Check whether object is being actively simulated, or sleeping.
auto getCanSleep() -> bool override
Check if this object can be de-activated (i.e. sleep).
void setMotionType(MotionType mt) override
Set the MotionType of the object.
auto contactTest() -> bool override
Return result of a discrete contact test between the object and collision world.
void clampJointLimits() override
clamp current pose to joint limits
void overrideCollisionGroup(CollisionGroup group) override
Manually set the collision group for all links of the object.
auto supportsSingleDofJointMotor(int linkIx) const -> bool
auto createJointMotor(int linkIndex, const JointMotorSettings& settings) -> int override
Create a new JointMotor from a JointMotorSettings.
void removeJointMotor(int motorId) override
Remove and destroy a joint motor.
void updateJointMotor(int motorId, const JointMotorSettings& settings) override
Update a JointMotor with new settings.
auto createMotorsForAllDofs(const JointMotorSettings& settings = JointMotorSettings()) -> std::unordered_map<int, int> override
Create a new set of default JointMotors for all valid dofs in an ArticulatedObject.
void updateAllMotorTargets(const std::vector<float>& stateTargets, bool velocities = false) override
Update all motors targets for this object's joints which support motors (Revolute, Prismatic, Spherical) from a state array.
void resetStateFromSceneInstanceAttr() override
Set or reset the articulated object's state using the object's specified sceneAOInstanceAttributes_ (down cast in method).

Public variables

std::unique_ptr<btMultiBody> btMultiBody_
The Bullet multibody structure.

Protected functions

void setRootState(const Magnum::Matrix4& state) override
Called internally from syncPose() Used to update physics constructs when kinematic transformations are performed manually. See esp::physics::PhysicsObjectBase for the transformations.
void updateKinematicState()

Protected variables

int nextJointMotorId_
std::unordered_map<int, std::unique_ptr<btMultiBodyJointMotor>> articulatedJointMotors
std::unordered_map<int, std::unique_ptr<btMultiBodySphericalJointMotor>> articulatedSphericalJointMotors
std::unordered_map<int, JointLimitConstraintInfo> jointLimitConstraints
maps local link id to parent joint's limit constraint
btAlignedObjectArray<btQuaternion> scratch_q_
btAlignedObjectArray<btVector3> scratch_m_
std::shared_ptr<btMultiBodyDynamicsWorld> bWorld_
The containing Bullet world.
std::unique_ptr<btCompoundShape> bFixedObjectShape_
The collision shape for the fixed base rigid object.
std::unique_ptr<btRigidBody> bFixedObjectRigidBody_
A proxy rigid object to replace fixed base links as a perf optimization.
std::map<int, std::unique_ptr<btCompoundShape>> linkCompoundShapes_
std::map<int, std::vector<std::unique_ptr<btCollisionShape>>> linkChildShapes_
std::shared_ptr<std::map<const btCollisionObject*, int>> collisionObjToObjIds_

Function documentation

void esp::physics::BulletArticulatedObject::initializeFromURDF(URDFImporter& u2b, const Magnum::Matrix4& worldTransform, scene::SceneNode* physicsNode) override

Initialize this ArticulatedObject from a parsed URDF stored in a URDFImporter. Creates a btMultiBody.

Parameters
u2b The BulletURDFImporter which will initialize this object from a parsed URDF file.
worldTransform Desired global root state of the ArticulatedObject.
physicsNode The parent node of this object.

void esp::physics::BulletArticulatedObject::constructStaticRigidBaseObject()

Construct a Static btRigidObject to act as a proxy collision object for the fixed base.

This optimization reduces the collision island size for articulated objects with heavy branching (e.g. a counter with many drawers) resulting in better sleeping behavior (e.g. contact with the countertop should not activate all drawers and contained objects).

To utilize this feature, the object URDF should mark fixed link collision shapes as part of the Static collision group (e.g. <collision group="2">)

std::shared_ptr<metadata::attributes::SceneAOInstanceAttributes> esp::physics::BulletArticulatedObject::getCurrentStateInstanceAttr() override

Return a metadata::attributes::SceneAOInstanceAttributes reflecting the current state of this Articulated Object.

Returns a SceneAOInstanceAttributes reflecting this Articulated Object's current state

Mn::Vector3 esp::physics::BulletArticulatedObject::getRootLinearVelocity() const override

Get the linear velocity of the articulated object's root in the global frame.

Returns The root linear velocity.

void esp::physics::BulletArticulatedObject::setRootLinearVelocity(const Mn::Vector3& linVel) override

Set the linear velocity of the articulated object's root in the global frame.

Parameters
linVel The root linear velocity.

Mn::Vector3 esp::physics::BulletArticulatedObject::getRootAngularVelocity() const override

Get the angular velocity (omega) of the articulated object's root in the global frame.

Returns The root angular velocity (omega).

void esp::physics::BulletArticulatedObject::setRootAngularVelocity(const Mn::Vector3& angVel) override

Set the angular velocity (omega) of the articulated object's root in the global frame.

Parameters
angVel The root angular velocity (omega).

void esp::physics::BulletArticulatedObject::setJointForces(const std::vector<float>& forces) override

Set forces/torques for all joints indexed by degrees of freedom.

Parameters
forces The desired joint forces/torques.

Bullet clears joint forces/torques with each simulation step.

void esp::physics::BulletArticulatedObject::addJointForces(const std::vector<float>& forces) override

Add forces/torques to all joints indexed by degrees of freedom.

Parameters
forces The desired joint forces/torques to add.

Bullet clears joint forces/torques with each simulation step.

std::vector<float> esp::physics::BulletArticulatedObject::getJointForces() override

Get current forces/torques for all joints indexed by degrees of freedom.

Returns The current joint forces/torques.

Bullet clears joint forces/torques with each simulation step.

void esp::physics::BulletArticulatedObject::setJointVelocities(const std::vector<float>& vels) override

Set velocities for all joints indexed by degrees of freedom.

Parameters
vels The desired joint velocities.

std::vector<float> esp::physics::BulletArticulatedObject::getJointVelocities() override

Get current velocities for all joints indexed by degrees of freedom.

Returns The current joint velocities.

void esp::physics::BulletArticulatedObject::setJointPositions(const std::vector<float>& positions) override

Set positions for all joints.

Parameters
positions The desired joint positions.

Note that positions are not indexed by DoF because some joints (spherical) have a different number of DoFs from positions. For spherical joints, a block of 4 position values should specify the state as a unit quaternion (x y z w).

std::vector<float> esp::physics::BulletArticulatedObject::getJointPositions() override

Get positions for all joints.

Returns The current joint positions.

Note that positions are not indexed by DoF because some joints (spherical) have a different number of DoFs from positions. For spherical joints, a block of 4 position values should specify the state as a unit quaternion (x y z w).

std::vector<float> esp::physics::BulletArticulatedObject::getJointMotorTorques(double fixedTimeStep) override

Get the torques on each joint.

Parameters
fixedTimeStep The physics timestep used by the simulator. Necessary to convert impulse into torque.
Returns Array of torques on each joint

std::pair<std::vector<float>, std::vector<float>> esp::physics::BulletArticulatedObject::getJointPositionLimits() override

Get position limits for all joints. (lower, upper)

Returns The active joint position limits as a pair of vectors (lower, upper). When no limit is set, entry is inf or -inf.

void esp::physics::BulletArticulatedObject::addArticulatedLinkForce(int linkId, Magnum::Vector3 force) override

Add linear force to a link's COM specified in the global frame.

Parameters
linkId The link's index.
force The desired force to add.

float esp::physics::BulletArticulatedObject::getArticulatedLinkFriction(int linkId) override

Get the friction coefficient for a link.

Parameters
linkId The link's index.
Returns The link's friction coefficient.

void esp::physics::BulletArticulatedObject::setArticulatedLinkFriction(int linkId, float friction) override

Set the friction coefficient for a link.

Parameters
linkId The link's index.
friction The link's friction coefficient.

JointType esp::physics::BulletArticulatedObject::getLinkJointType(int linkId) const override

Get the type of the link's parent joint.

Parameters
linkId The link's index.
Returns The link's parent joint's type.

int esp::physics::BulletArticulatedObject::getLinkDoFOffset(int linkId) const override

Get the starting position for this link's parent joint in the global DoFs array.

Parameters
linkId The link's index.
Returns The link's starting DoF index.

int esp::physics::BulletArticulatedObject::getLinkNumDoFs(int linkId) const override

Get the number of DoFs for this link's parent joint.

Parameters
linkId The link's index.
Returns The number of DoFs for this link's parent joint.

int esp::physics::BulletArticulatedObject::getLinkJointPosOffset(int linkId) const override

Get the starting position for this link's parent joint in the global positions array.

Parameters
linkId The link's index.
Returns The link's starting position index.

int esp::physics::BulletArticulatedObject::getLinkNumJointPos(int linkId) const override

Get the number of positions for this link's parent joint.

Parameters
linkId The link's index.
Returns The number of positions for this link's parent joint.

void esp::physics::BulletArticulatedObject::setActive(bool active) override

Set an object as being actively simulated or sleeping.

Parameters
active Whether to activate or sleep the object

bool esp::physics::BulletArticulatedObject::isActive() const override

Check whether object is being actively simulated, or sleeping.

Returns true if active, false otherwise.

bool esp::physics::BulletArticulatedObject::getCanSleep() override

Check if this object can be de-activated (i.e. sleep).

Returns Whether or not the object is able to deactivate.

void esp::physics::BulletArticulatedObject::setMotionType(MotionType mt) override

Set the MotionType of the object.

Parameters
mt The desired MotionType.

Dynamic state is integrated by physics simulator. Kinematic state is manually set by user. Static state should not be changed. Object can be added to NavMesh.

bool esp::physics::BulletArticulatedObject::contactTest() override

Return result of a discrete contact test between the object and collision world.

Returns Whether or not the object is in contact with any other collision enabled objects.

See SimulationContactResultCallback

void esp::physics::BulletArticulatedObject::overrideCollisionGroup(CollisionGroup group) override

Manually set the collision group for all links of the object.

Parameters
group The desired CollisionGroup for the object.

bool esp::physics::BulletArticulatedObject::supportsSingleDofJointMotor(int linkIx) const

Bullet supports vel/pos control joint motors for revolute and prismatic joints (1 Dof) This is the suggested way to implement friction/damping at dof level

int esp::physics::BulletArticulatedObject::createJointMotor(int linkIndex, const JointMotorSettings& settings) override

Create a new JointMotor from a JointMotorSettings.

Parameters
linkIndex the index of the link for which the parent joint will have a motor attached
settings The settings for the joint motor. Must have JointMotorType correctly configured for the target joint.
Returns The motorId for the new joint motor

Note: No base implementation. See BulletArticulatedObject.

std::unordered_map<int, int> esp::physics::BulletArticulatedObject::createMotorsForAllDofs(const JointMotorSettings& settings = JointMotorSettings()) override

Create a new set of default JointMotors for all valid dofs in an ArticulatedObject.

Returns A map of motorIds to link/joint indices for the new motors.

Note: No base implementation. See BulletArticulatedObject.

void esp::physics::BulletArticulatedObject::updateAllMotorTargets(const std::vector<float>& stateTargets, bool velocities = false) override

Update all motors targets for this object's joints which support motors (Revolute, Prismatic, Spherical) from a state array.

Parameters
stateTargets Full length joint position or velocity array for this object.
velocities Whether to interpret stateTargets as velocities or positions.

By default, state is interpreted as position targets unless velocities is specified. Expected input is the full length position or velocity array for this object. This function will safely skip states for joints which don't support JointMotors.

Note: No base implementation. See BulletArticulatedObject.

void esp::physics::BulletArticulatedObject::updateKinematicState() protected

Performs forward kinematics, updates collision object states and broadphase aabbs for the object. Do this with manual state setters.