Namespaces  
benchmarks  
constraint  
contact_solvers  
fem  
hydroelastics  
meshcat  
parsing  
test  
test_utilities  
Classes  
struct  AddMultibodyPlantSceneGraphResult 
Temporary result from AddMultibodyPlantSceneGraph . More...  
class  AngleBetweenVectorsConstraint 
Constrains that the angle between a vector a and another vector b is between [θ_lower, θ_upper]. More...  
class  AngleBetweenVectorsCost 
Implements a cost of the form c*(1cosθ), where θ is the angle between two vectors a and b . More...  
class  ArticulatedBodyInertia 
Articulated Body Inertia is the inertia that a body appears to have when it is the base (or root) of a rigidbody system, also referred to as Articulated Body in the context of articulated body algorithms. More...  
class  BallRpyJoint 
This Joint allows two bodies to rotate freely relative to one another. More...  
class  Body 
Body provides the general abstraction of a body with an API that makes no assumption about whether a body is rigid or deformable and neither does it make any assumptions about the underlying physical model or approximation. More...  
class  BodyFrame 
A BodyFrame is a material Frame that serves as the unique reference frame for a Body. More...  
struct  CalcGridPointsOptions 
class  CentroidalMomentumConstraint 
Impose the constraint CentroidalMomentum(q, v)  h_WC = 0 with decision variables [q;v;h_WC] or CentroidalAngularMomentum(q, v)  k_WC = 0 with decision variables [q; v; k_WC] h_WC is the 6D spatial momentum (linear and angular momentum about the center of mass C) expressed in the world frame (W). More...  
class  ComInPolyhedronConstraint 
Constrains the center of mass to lie within a polyhedron lb <= A * p_EC <= ub where p_EC is the position of the centerofmass (C) expressed in a frame E. More...  
class  ComPositionConstraint 
Impose the constraint p_EScm(q)  p_EC = 0, where p_EScm(q) is a function that computes the centerofmass (COM) position from robot generalized position q, expressed in a frame E. More...  
class  ContactResults 
A container class storing the contact results information for each contact pair for a given state of the simulation. More...  
class  ContactResultsToLcmSystem 
A System that encodes ContactResults into a lcmt_contact_results_for_viz message. More...  
struct  ContactWrench 
Stores the contact wrench (spatial force) from Body A to Body B applied at point Cb. More...  
class  ContactWrenchEvaluator 
class  ContactWrenchFromForceInWorldFrameEvaluator 
The contact wrench is τ_AB_W = 0, f_AB_W = λ Namely we assume that λ is the contact force from A to B, applied directly at B's witness point. More...  
class  CoulombFriction 
Parameters for Coulomb's Law of Friction, namely: More...  
class  DeformableModel 
DeformableModel implements the interface in PhysicalModel and provides the functionalities to specify deformable bodies. More...  
class  DistanceConstraint 
Constrains the distance between a pair of geometries to be within a range [distance_lower, distance_upper]. More...  
class  DoorHinge 
This ForceElement models a revolute DoorHinge joint that could exhibit different force/torque characteristics at different states due to the existence of different type of torques on the joint. More...  
struct  DoorHingeConfig 
Configuration structure for the DoorHinge. More...  
struct  ExternallyAppliedSpatialForce 
class  ExternallyAppliedSpatialForceMultiplexer 
Concatenates multiple std::vector<>'s of ExternallyAppliedSpatialForce<T>. More...  
class  FixedOffsetFrame 
FixedOffsetFrame represents a material frame F whose pose is fixed with respect to a parent material frame P. More...  
class  ForceElement 
A ForceElement allows modeling state and time dependent forces in a MultibodyTree model. More...  
class  Frame 
Frame is an abstract class representing a material frame (also called a physical frame), meaning that the Frame's origin is a material point of a Body. More...  
class  FrameBase 
FrameBase is an abstract representation of the concept of a frame in multibody dynamics. More...  
class  GaussianTriangleQuadratureRule 
class  GazeTargetConstraint 
Constrains a target point T to be within a cone K. More...  
struct  GeometryPairContactWrenchEvaluatorBinding 
class  GlobalInverseKinematics 
Solves the inverse kinematics problem as a mixed integer convex optimization problem. More...  
class  HydroelasticContactInfo 
A class containing information regarding contact and contact response between two geometries attached to a pair of bodies. More...  
struct  HydroelasticQuadraturePointData 
Results from intermediate calculations used during the quadrature routine. More...  
class  InverseKinematics 
Solves an inverse kinematics (IK) problem on a MultibodyPlant, to find the postures of the robot satisfying certain constraints. More...  
class  Joint 
A Joint models the kinematical relationship which characterizes the possible relative motion between two bodies. More...  
class  JointActuator 
The JointActuator class is mostly a simple bookkeeping structure to represent an actuator acting on a given Joint. More...  
class  LinearBushingRollPitchYaw 
This ForceElement models a massless flexible bushing that connects a frame A of a link (body) L0 to a frame C of a link (body) L1. More...  
class  LinearSpringDamper 
This ForceElement models a springdamper attached between two points on two different bodies. More...  
class  ManipulatorEquationConstraint 
A Constraint to impose the manipulator equation: 0 = (Buₙ₊₁ + ∑ᵢ (Jᵢ_WBᵀ(qₙ₊₁)ᵀ * Fᵢ_AB_W(λᵢ,ₙ₊₁)) More...  
class  MinimumDistanceConstraint 
Constrain the signed distance between all candidate pairs of geometries (according to the logic of SceneGraphInspector::GetCollisionCandidates()) to be no smaller than a specified minimum distance. More...  
class  MultibodyElement 
A class representing an element (subcomponent) of a MultibodyPlant or (internally) a MultibodyTree. More...  
class  MultibodyForces 
A class to hold a set of forces applied to a MultibodyTree system. More...  
class  MultibodyPlant 
MultibodyPlant is a Drake system framework representation (see systems::System) for the model of a physical system consisting of a collection of interconnected bodies. More...  
struct  MultibodyPlantConfig 
The set of configurable properties on a MultibodyPlant. More...  
class  MultibodyPlantTester 
class  OrientationConstraint 
Constrains that the angle difference θ between the orientation of frame A and the orientation of frame B to satisfy θ ≤ θ_bound. More...  
class  OrientationCost 
Implements a cost of the form c * (1  cos(θ)) , where θ is the angle between the orientation of frame A and the orientation of frame B, and c is a cost scaling. More...  
class  PackageMap 
Maps ROS package names to their full path on the local file system. More...  
class  Parser 
Parses model description input into a MultibodyPlant and (optionally) a SceneGraph. More...  
class  PhysicalModel 
(Internal) PhysicalModel provides the functionalities to extend the type of physical model of MultibodyPlant. More...  
class  PlanarJoint 
This joint models a planar joint allowing two bodies to translate and rotate relative to one another in a plane with three degrees of freedom. More...  
class  PointPairContactInfo 
A class containing information regarding contact response between two bodies including: More...  
class  PointToPointDistanceConstraint 
Constrain that the distance between a point P1 on frame B1 and another point P2 on frame B2 is within a range [distance_lower, distance_upper]. More...  
class  PolyhedronConstraint 
Constrain the position of points P1, P2, ..., Pn to satisfy the constraint A. More...  
class  PositionConstraint 
Constrains the position of a point Q, rigidly attached to a frame B, to be within a bounding box measured and expressed in frame A. More...  
class  PositionCost 
Implements a cost of the form (p_AP  p_AQ)ᵀ C (p_AP  p_AQ), where point P is specified relative to frame A and point Q is specified relative to frame B, and the cost is evaluated in frame A. More...  
class  PrismaticJoint 
This Joint allows two bodies to translate relative to one another along a common axis. More...  
class  PrismaticSpring 
This ForceElement models a linear spring attached to a PrismaticJoint and applies a force to that joint according to. More...  
class  Propeller 
A System that connects to the MultibodyPlant in order to model the effects of one or more controlled propellers acting on a Body. More...  
struct  PropellerInfo 
Parameters that describe the kinematic frame and forceproduction properties of a single propeller. More...  
class  QuaternionEulerIntegrationConstraint 
If we have a body with orientation quaternion z₁ at time t₁, and a quaternion z₂ at time t₂ = t₁ + h, with the angular velocity ω (expressed in the world frame), we impose the constraint that the body rotates at a constant velocity ω from quaternion z₁ to quaternion z₂ within time interval h. More...  
class  QuaternionFloatingJoint 
This Joint allows two bodies to move freely relatively to one another. More...  
class  RationalForwardKinematics 
For certain robots (whose joint transforms are algebraic functions of joint variables, for example revolute/prismatic/floatingbase joints), we can represent the pose (position, orientation) of each body, as rational functions, namely n(s) / d(s) where both the numerator n(s) and denominator d(s) are polynomials of s, and s is some variable related to the generalized position. More...  
class  RevoluteJoint 
This Joint allows two bodies to rotate relatively to one another around a common axis. More...  
class  RevoluteSpring 
This ForceElement models a torsional spring attached to a RevoluteJoint and applies a torque to that joint. More...  
class  RigidBody 
The term rigid body implies that the deformations of the body under consideration are so small that they have no significant effect on the overall motions of the body and therefore deformations can be neglected. More...  
class  RotationalInertia 
This class describes the mass distribution (inertia properties) of a body or composite body about a particular point. More...  
class  ScrewJoint 
This joint models a screw joint allowing two bodies to rotate about one axis while translating along that same axis with one degree of freedom. More...  
struct  SignedDistanceWithTimeDerivative 
The struct containing the signed distance and its time derivative between a pair of geometries. More...  
class  SpatialAcceleration 
This class represents a spatial acceleration A and has 6 elements with an angular (rotational) acceleration α (3element vector) on top of a translational (linear) acceleration 𝐚 (3element vector). More...  
class  SpatialForce 
This class represents a spatial force F (also called a wrench) and has 6 elements with a torque 𝛕 (3element vector) on top of a force 𝐟 (3element vector). More...  
class  SpatialInertia 
This class represents the physical concept of a Spatial Inertia. More...  
class  SpatialMomentum 
This class represents a spatial momentum L and has 6 elements with an angular (rotational) momentum 𝐡 (3element vector) on top of a translational (linear) momentum 𝐥 (3element vector). More...  
class  SpatialVector 
This class represents a spatial vector and has 6 elements, with a 3element rotational vector on top of a 3element translational vector. More...  
class  SpatialVelocity 
This class represents a spatial velocity V (also called a twist) and has 6 elements with an angular (rotational) velocity ω (3element vector) on top of a translational (linear) velocity v (3element vector). More...  
class  SpatialVelocityConstraint 
Constrains the spatial velocity of a frame C, rigidly attached to a frame B, measured and expressed in frame A. More...  
class  StaticEquilibriumConstraint 
Impose the static equilibrium constraint 0 = τ_g + Bu + ∑J_WBᵀ(q) * Fapp_B_W. More...  
class  StaticEquilibriumProblem 
Finds the static equilibrium pose of a multibody system through optimization. More...  
class  StaticFrictionConeConstraint 
Formulates the nonlinear friction cone constraint fₜ ≤ μ*fₙ, where fₜ is the tangential contact force, fₙ is the normal contact force, and μ is the friction coefficient. More...  
class  TamsiSolver 
struct  TamsiSolverIterationStats 
Struct used to store information about the iteration process performed by TamsiSolver. More...  
struct  TamsiSolverParameters 
These are the parameters controlling the iteration process of the TamsiSolver solver. More...  
class  Toppra 
Solves a Time Optimal Path Parameterization based on Reachability Analysis (TOPPRA) to find the fastest traversal of a given path, satisfying the given constraints. More...  
class  TriangleQuadrature 
A class for integrating a function using numerical quadrature over triangular domains. More...  
class  TriangleQuadratureRule 
A "rule" (weights and quadrature points) for computing quadrature over triangular domains. More...  
class  UniformGravityFieldElement 
This ForceElement allows modeling the effect of a uniform gravity field as felt by bodies on the surface of the Earth. More...  
class  UnitInertia 
This class is used to represent rotational inertias for unit mass bodies. More...  
class  UnitQuaternionConstraint 
Constrains the quaternion to have a unit length. More...  
class  UniversalJoint 
This joint models a universal joint allowing two bodies to rotate relative to one another with two degrees of freedom. More...  
class  WeldJoint 
This Joint fixes the relative pose between two frames as if "welding" them together. More...  
class  Wing 
A System that connects to the MultibodyPlant in order to model the simplified dynamics of an airfoil (or hydrofoil). More...  
Typedefs  
using  MinimumDistancePenaltyFunction = solvers::MinimumValuePenaltyFunction 
Computes the penalty function φ(x) and its derivatives dφ(x)/dx. More...  
using  DeformableBodyId = Identifier< class DeformableBodyTag > 
Uniquely identifies a deformable body. More...  
using  DeformableBodyIndex = TypeSafeIndex< class DeformableBodyTag > 
Internally indexes deformable bodies, only used after Finalize(). More...  
template<typename T >  
using  PhysicalModelPointerVariant = std::variant< const DeformableModel< T > *, std::monostate > 
using  FrameIndex = TypeSafeIndex< class FrameTag > 
Type used to identify frames by index in a multibody tree system. More...  
using  BodyIndex = TypeSafeIndex< class BodyTag > 
Type used to identify bodies by index in a multibody tree system. More...  
using  ForceElementIndex = TypeSafeIndex< class ForceElementTag > 
Type used to identify force elements by index within a multibody tree system. More...  
using  JointIndex = TypeSafeIndex< class JointElementTag > 
Type used to identify joints by index within a multibody tree system. More...  
using  JointActuatorIndex = TypeSafeIndex< class JointActuatorElementTag > 
Type used to identify actuators by index within a multibody tree system. More...  
using  ConstraintIndex = TypeSafeIndex< class ConstraintTag > 
Type used to identify constraints by index within a multibody system. More...  
using  ModelInstanceIndex = TypeSafeIndex< class ModelInstanceTag > 
Type used to identify model instances by index within a multibody tree system. More...  
Enumerations  
enum  ToppraDiscretization { kCollocation, kInterpolation } 
Selects how linear constraints are enforced for TOPPRA's optimization. More...  
enum  ContactModel { kHydroelastic, kPoint, kHydroelasticWithFallback, kHydroelasticsOnly = kHydroelastic, kPointContactOnly = kPoint } 
Enumeration for contact model options. More...  
enum  DiscreteContactSolver { kTamsi, kSap } 
The type of the contact solver used for a discrete MultibodyPlant model. More...  
enum  TamsiSolverResult { kSuccess = 0, kMaxIterationsReached = 1, kLinearSolverFailed = 2 } 
The result from TamsiSolver::SolveWithGuess() used to report the success or failure of the solver. More...  
enum  JacobianWrtVariable { kQDot, kV } 
Enumeration that indicates whether the Jacobian is partial differentiation with respect to q̇ (timederivatives of generalized positions) or with respect to v (generalized velocities). More...  
Functions  
template<typename T >  
void  AddUnitQuaternionConstraintOnPlant (const MultibodyPlant< T > &plant, const Eigen::Ref< const VectorX< symbolic::Variable >> &q_vars, solvers::MathematicalProgram *prog)  
Add unit length constraints to all the variables representing quaternion in q_vars . More...  
std::pair< solvers::Binding< internal::SlidingFrictionComplementarityNonlinearConstraint >, solvers::Binding< StaticFrictionConeConstraint > >  AddSlidingFrictionComplementarityExplicitContactConstraint (const ContactWrenchEvaluator *contact_wrench_evaluator, double complementarity_tolerance, const Eigen::Ref< const VectorX< symbolic::Variable >> &q_vars, const Eigen::Ref< const VectorX< symbolic::Variable >> &v_vars, const Eigen::Ref< const VectorX< symbolic::Variable >> &lambda_vars, solvers::MathematicalProgram *prog)  
For a pair of geometries in explicit contact, adds the sliding friction complementarity constraint explained in sliding_friction_complementarity_constraint to an optimization program. More...  
std::pair< solvers::Binding< internal::SlidingFrictionComplementarityNonlinearConstraint >, solvers::Binding< internal::StaticFrictionConeComplementarityNonlinearConstraint > >  AddSlidingFrictionComplementarityImplicitContactConstraint (const ContactWrenchEvaluator *contact_wrench_evaluator, double complementarity_tolerance, const Eigen::Ref< const VectorX< symbolic::Variable >> &q_vars, const Eigen::Ref< const VectorX< symbolic::Variable >> &v_vars, const Eigen::Ref< const VectorX< symbolic::Variable >> &lambda_vars, solvers::MathematicalProgram *prog)  
For a pair of geometries in implicit contact (they may or may not be in contact, adds the sliding friction complementarity constraint explained in sliding_friction_complementarity_constraint. More...  
solvers::Binding< internal::StaticFrictionConeComplementarityNonlinearConstraint >  AddStaticFrictionConeComplementarityConstraint (const ContactWrenchEvaluator *contact_wrench_evaluator, double complementarity_tolerance, const Eigen::Ref< const VectorX< symbolic::Variable >> &q_vars, const Eigen::Ref< const VectorX< symbolic::Variable >> &lambda_vars, solvers::MathematicalProgram *prog)  
Adds the complementarity constraint on the static friction force between a pair of contacts ft_W <= μ * n_Wᵀ * f_W (static friction force in the friction cone). More...  
SignedDistanceWithTimeDerivative  CalcDistanceAndTimeDerivative (const multibody::MultibodyPlant< double > &plant, const SortedPair< geometry::GeometryId > &geometry_pair, const systems::Context< double > &context)  
Given a pair of geometries and the generalized position/velocity of the plant, compute the signed distance between the pair of geometries and the time derivative of the signed distance. More...  
template<typename T >  
CoulombFriction< T >  CalcContactFrictionFromSurfaceProperties (const CoulombFriction< T > &surface_properties1, const CoulombFriction< T > &surface_properties2)  
Given the surface properties of two different surfaces, this method computes the Coulomb's law coefficients of friction characterizing the interaction by friction of the given surface pair. More...  
template<typename T >  
bool  operator== (const HydroelasticQuadraturePointData< T > &data1, const HydroelasticQuadraturePointData< T > &data2)  
Returns true if all of the corresponding individual fields of data1 and data2 are equal (i.e., using their corresponding operator==() functions). More...  
AddMultibodyPlantSceneGraphResult< double >  AddMultibodyPlant (const MultibodyPlantConfig &config, systems::DiagramBuilder< double > *builder)  
Adds a new MultibodyPlant and SceneGraph to the given builder . More...  
SpatialInertia< double >  CalcSpatialInertia (const geometry::Shape &shape, double density)  
Computes the SpatialInertia of a body made up of a homogeneous material (of given density in kg/m³) uniformly distributed in the volume of the given shape . More...  
SpatialInertia< double >  CalcSpatialInertia (const geometry::TriangleSurfaceMesh< double > &mesh, double density=1.0)  
Computes the SpatialInertia of a body made up of a homogeneous material (of given density in kg/m³) uniformly distributed in the volume of the given mesh . More...  
BodyIndex  world_index ()  
For every MultibodyPlant the world body always has this unique index and it is always zero. More...  
FrameIndex  world_frame_index ()  
For every MultibodyPlant the world frame always has this unique index and it is always zero. More...  
ModelInstanceIndex  world_model_instance ()  
Returns the model instance containing the world body. More...  
ModelInstanceIndex  default_model_instance ()  
Returns the model instance which contains all tree elements with no explicit model instance specified. More...  
Visualizing contact results  
These functions extend a Diagram with the required components to publish contact results (as reported by MultibodyPlant) to a visualizer (either meldis or drake_visualizer). We recommend using these functions instead of assembling the requisite components by hand. These must be called during Diagram building. Each function makes modifications to the diagram being constructed by
The two overloads differ in the following way:
The parameters have the following semantics:
 
systems::lcm::LcmPublisherSystem *  ConnectContactResultsToDrakeVisualizer (systems::DiagramBuilder< double > *builder, const MultibodyPlant< double > &plant, const geometry::SceneGraph< double > &scene_graph, lcm::DrakeLcmInterface *lcm=nullptr, std::optional< double > publish_period=std::nullopt)  
MultibodyPlantconnecting overload. More...  
systems::lcm::LcmPublisherSystem *  ConnectContactResultsToDrakeVisualizer (systems::DiagramBuilder< double > *builder, const MultibodyPlant< double > &plant, const geometry::SceneGraph< double > &scene_graph, const systems::OutputPort< double > &contact_results_port, lcm::DrakeLcmInterface *lcm=nullptr, std::optional< double > publish_period=std::nullopt)  
OutputPortconnecting overload. More...  
using BodyIndex = TypeSafeIndex<class BodyTag> 
Type used to identify bodies by index in a multibody tree system.
using ConstraintIndex = TypeSafeIndex<class ConstraintTag> 
Type used to identify constraints by index within a multibody system.
using DeformableBodyId = Identifier<class DeformableBodyTag> 
Uniquely identifies a deformable body.
It is valid before and after Finalize().
using DeformableBodyIndex = TypeSafeIndex<class DeformableBodyTag> 
Internally indexes deformable bodies, only used after Finalize().
using ForceElementIndex = TypeSafeIndex<class ForceElementTag> 
Type used to identify force elements by index within a multibody tree system.
using FrameIndex = TypeSafeIndex<class FrameTag> 
Type used to identify frames by index in a multibody tree system.
using JointActuatorIndex = TypeSafeIndex<class JointActuatorElementTag> 
Type used to identify actuators by index within a multibody tree system.
using JointIndex = TypeSafeIndex<class JointElementTag> 
Type used to identify joints by index within a multibody tree system.
Computes the penalty function φ(x) and its derivatives dφ(x)/dx.
Valid penalty functions must meet the following criteria:
using ModelInstanceIndex = TypeSafeIndex<class ModelInstanceTag> 
Type used to identify model instances by index within a multibody tree system.
using PhysicalModelPointerVariant = std::variant<const DeformableModel<T>*, std::monostate> 

strong 
Enumeration for contact model options.
Enumerator  

kHydroelastic  Contact forces are computed using the Hydroelastic model. Contact between unsupported geometries will cause a runtime exception. 
kPoint  Contact forces are computed using a point contact model, see Numerical Approximation of Point Contact. 
kHydroelasticWithFallback  Contact forces are computed using the hydroelastic model, where possible. For most other unsupported colliding pairs, the point model from kPoint is used. See geometry::QueryObject::ComputeContactSurfacesWithFallback for more details. 
kHydroelasticsOnly  Legacy alias. TODO(jwnimmertri) Deprecate this constant. 
kPointContactOnly  Legacy alias. TODO(jwnimmertri) Deprecate this constant. 

strong 
The type of the contact solver used for a discrete MultibodyPlant model.
Note: the SAP solver only fully supports scalar type double
. For scalar type AutoDiffXd
, the SAP solver throws if any constraint (including contact) is detected. As a consequence, one can only run dynamic simulations without any constraints under the combination of SAP and AutoDiffXd
. The SAP solver does not support symbolic calculations.
Enumerator  

kTamsi  TAMSI solver, see [Castro et al., 2019]. 
kSap  SAP solver, see [Castro et al., 2022]. 

strong 

strong 
The result from TamsiSolver::SolveWithGuess() used to report the success or failure of the solver.

strong 
Selects how linear constraints are enforced for TOPPRA's optimization.
kCollocation  enforces constraints only at each gridpoint. kInterpolation  enforces constrants at each gridpoint and at the following gridpoint using forward integration. Yields higher accuracy at minor computational cost.
Enumerator  

kCollocation  
kInterpolation 
AddMultibodyPlantSceneGraphResult<double> drake::multibody::AddMultibodyPlant  (  const MultibodyPlantConfig &  config, 
systems::DiagramBuilder< double > *  builder  
) 
Adds a new MultibodyPlant and SceneGraph to the given builder
.
The plant's settings such as time_step
are set using the given config
.
void drake::multibody::AddUnitQuaternionConstraintOnPlant  (  const MultibodyPlant< T > &  plant, 
const Eigen::Ref< const VectorX< symbolic::Variable >> &  q_vars,  
solvers::MathematicalProgram *  prog  
) 
Add unit length constraints to all the variables representing quaternion in q_vars
.
Namely the quaternions for floating base joints in plant
will be enforced to have a unit length.
plant  The plant on which we impose the unit quaternion constraints. 
q_vars  The decision variables for the generalized position of the plant. 
prog  The unit quaternion constraints are added to this prog. 
T  The scalar type, which must be one of the default scalars. 
CoulombFriction<T> drake::multibody::CalcContactFrictionFromSurfaceProperties  (  const CoulombFriction< T > &  surface_properties1, 
const CoulombFriction< T > &  surface_properties2  
) 
Given the surface properties of two different surfaces, this method computes the Coulomb's law coefficients of friction characterizing the interaction by friction of the given surface pair.
The surface properties are specified by individual Coulomb's law coefficients of friction. As outlined in the class's documentation for CoulombFriction, friction coefficients characterize a surface pair and not individual surfaces. However, we find it useful in practice to associate the abstract idea of friction coefficients to a single surface. Please refer to the documentation for CoulombFriction for details on this topic.
More specifically, this method computes the contact coefficients for the given surface pair as:
μ = 2μₘμₙ/(μₘ + μₙ)
where the operation above is performed separately on the static and dynamic friction coefficients.
[in]  surface_properties1  Surface properties for surface 1. Specified as an individual set of Coulomb's law coefficients of friction. 
[in]  surface_properties2  Surface properties for surface 2. Specified as an individual set of Coulomb's law coefficients of friction. 
SignedDistanceWithTimeDerivative drake::multibody::CalcDistanceAndTimeDerivative  (  const multibody::MultibodyPlant< double > &  plant, 
const SortedPair< geometry::GeometryId > &  geometry_pair,  
const systems::Context< double > &  context  
) 
Given a pair of geometries and the generalized position/velocity of the plant, compute the signed distance between the pair of geometries and the time derivative of the signed distance.
This function is similar to QueryObject::ComputeSignedDistancePairClosestPoints(), but it also provides the time derivative of the signed distance.
plant  The plant on which the geometries are attached. This plant must have been connected to a SceneGraph.  
geometry_pair  The pair of geometries whose distance and time derivative are computed.  
context  The context of the plant. This must store both q and v. This context must have been extracted from the diagram context which contains both MultibodyPlant and SceneGraph contexts.  
[out]  distance  The signed distance between the pair of geometry. 
[out]  distance_time_derivative  The time derivative of the signed distance. 
SpatialInertia<double> drake::multibody::CalcSpatialInertia  (  const geometry::Shape &  shape, 
double  density  
) 
Computes the SpatialInertia of a body made up of a homogeneous material (of given density
in kg/m³) uniformly distributed in the volume of the given shape
.
The shape
is defined in its canonical frame S and the body in frame B. The two frames are coincident and aligned (i.e., X_SB = I).
Most shapes are defined such that their center of mass is coincident with So (and, therefore, Bo). These are the shapes that have symmetry across So along each of the axes Sx, Sy, Sz (e.g., geometry::Box, geometry::Sphere, etc.) For meshes, it depends on how the mesh is defined. For more discussion on the nuances of geometry::Mesh and geometry::Convex calculations see below.
Note: Spatial inertia calculations for the geometry::Convex type do not currently require that the underlying mesh actually be convex. Although certain collision calculations involving geometry::Convex may use the mesh's convex hull, this function uses the actual mesh.
M_BBo_B  The spatial inertia of the hypothetical body implied by the given shape . 
std::exception  if shape is an instance of geometry::HalfSpace or geometry::MeshcatCone. 
SpatialInertia<double> drake::multibody::CalcSpatialInertia  (  const geometry::TriangleSurfaceMesh< double > &  mesh, 
double  density = 1.0 

) 
Computes the SpatialInertia of a body made up of a homogeneous material (of given density
in kg/m³) uniformly distributed in the volume of the given mesh
.
The mesh
is defined in its canonical frame M and the body in frame B. The two frames are coincident and aligned (i.e., X_MB = I).
For the resultant spatial inertia to be meaningful, the mesh
must satisfy certain requirements:
If these requirements are not met, a value will be returned, but its value is meaningless.
ModelInstanceIndex drake::multibody::default_model_instance  (  ) 
Returns the model instance which contains all tree elements with no explicit model instance specified.
bool drake::multibody::operator==  (  const HydroelasticQuadraturePointData< T > &  data1, 
const HydroelasticQuadraturePointData< T > &  data2  
) 
Returns true
if all of the corresponding individual fields of data1
and data2
are equal (i.e., using their corresponding operator==()
functions).
FrameIndex drake::multibody::world_frame_index  (  ) 
For every MultibodyPlant the world frame always has this unique index and it is always zero.
BodyIndex drake::multibody::world_index  (  ) 
For every MultibodyPlant the world body always has this unique index and it is always zero.
ModelInstanceIndex drake::multibody::world_model_instance  (  ) 
Returns the model instance containing the world body.
For every MultibodyPlant the world body always has this unique model instance and it is always zero (as described in #3088).