RigidLink#

class genesis.engine.entities.rigid_entity.rigid_link.RigidLink(entity: RigidEntity, idx: int, parent_idx: int, root_idx: int | None, joint_start: int, n_joints: int, geom_start: int, cell_start: int, vert_start: int, face_start: int, edge_start: int, free_verts_state_start: int, fixed_verts_state_start: int, vgeom_start: int, vvert_start: int, vface_start: int, visualize_contact: bool, desc: RigidLinkDescription)[source]#

Bases: KinematicLink

RigidLink class. One RigidEntity consists of multiple RigidLinks, each of which is a rigid body and could consist of multiple RigidGeoms (link.geoms, for collision) and RigidVisGeoms (link.vgeoms for visualization).

get_verts()[source]#: Get the vertices of the link’s collision body (concatenation of all link.geoms) in the world frame.

get_AABB()[source]#: Get the vertex-based axis-aligned bounding box (AABB) of the link’s collision body in the world frame by aggregating all the collision geometries associated with this link (link.geoms).

apply_external_wrench(force=None, torque=None, envs_idx=None, *, pos=None, ref: link_ref_frame = link_ref_frame.link_origin, local: bool = False)[source]#

Apply an external wrench over one simulation step on the link.

Parameters:

force (None | array_like, optional) – The linear force to apply. None for a pure torque. Defaults to None.
torque (None | array_like, optional) – The torque to apply, on top of the moment induced by the linear force. Defaults to None.
envs_idx (None | array_like, optional) – The indices of the environments. If None, all environments will be considered. Defaults to None.
pos (None | array_like, optional) – Where the linear force is applied, which sets the moment arm of the induced torque. With local=True, an offset from the origin of the ref frame, so the point follows the link as it moves; otherwise a world position. None applies the force at the origin of the ref frame. Defaults to None.
ref (gs.link_ref_frame, optional) – The reference frame: the origin of the link (‘link_origin’), or its center of mass (‘link_COM’). It fixes where the linear force acts when pos is None, and the axes of the input coordinates when local=True. Defaults to ‘link_origin’.
local (bool, optional) – Whether force, torque and pos are expressed in the coordinates of the ref frame rather than the world frame. Defaults to False.

apply_external_force(force, envs_idx=None, *, pos=None, ref: link_ref_frame = link_ref_frame.link_origin, local: bool = False)[source]#

Apply an external linear force over one simulation step on the link.

Refer to RigidLink.apply_external_wrench for details.

apply_external_torque(torque, envs_idx=None, *, ref: link_ref_frame = link_ref_frame.link_origin, local: bool = False)[source]#

Apply an external torque over one simulation step on the link.

Refer to RigidLink.apply_external_wrench for details.

set_mass(mass: tuple[float, ...])[source]#

Set the mass of the link, in kg.

The inertia of the link is left unchanged, so use set_inertia to change it too. RigidEntity.set_mass scales the inertia of every link of an entity instead, by the same factor as its mass, which is how a body of the same shape made heavier behaves.

Parameters:: mass (float | array_like, shape (n_envs,)) – The mass to set. Per-environment values require RigidOptions.batch_links_info=True.

set_COM(com)[source]#

Set the center of mass (COM) of the link, as an offset in the link’s local frame.

Parameters:: com (array_like, shape (3,) or (n_envs, 3)) – The center of mass to set. Per-environment values require RigidOptions.batch_links_info=True.

set_inertia(inertia)[source]#

Set the inertia matrix of the link, expressed in its inertial frame.

Parameters:: inertia (array_like, shape (3, 3) or (n_envs, 3, 3)) – The inertia matrix to set, which must be symmetric positive definite. Per-environment values require RigidOptions.batch_links_info=True.

get_invweight(envs_idx=None)[source]#

Get the constraint inverse weights of the link: one for forces, one for torques.

See RigidEntity.get_links_invweight for what an inverse weight is and where its value comes from.

Parameters:: envs_idx (None | array_like, optional) – The indices of the environments. If None, all environments are returned. Defaults to None.
Returns:: invweight – The translational and rotational inverse weight of the link, per environment for a batched scene whose link info is batched.
Return type:: torch.Tensor, shape (2,) or (n_envs, 2)

get_mass(envs_idx=None)[source]#

Get the mass of the link, in kg.

Parameters:: envs_idx (None | array_like, optional) – The indices of the environments. If None, all environments are returned. Defaults to None.
Returns:: mass – The mass of the link, per environment for a batched scene whose link info is batched.
Return type:: torch.Tensor, shape (n_envs,) or scalar

set_friction(friction)[source]#: Set the friction of all the link’s geoms.

set_friction_torsional(friction_torsional)[source]#: Set the torsional friction of all the link’s geoms (see ‘gs.materials.Rigid’).

set_friction_rolling(friction_rolling)[source]#: Set the rolling friction of all the link’s geoms (see ‘gs.materials.Rigid’).

property visualize_contact: bool#: Whether to visualize the contact of the link.

property geoms: list[genesis.engine.entities.rigid_entity.rigid_geom.RigidGeom]#: The list of the link’s collision geometries (RigidGeom).

property n_geoms: int#: Number of the link’s collision geometries.

property geom_start: int#: The start index of the link’s collision geometries in the RigidSolver.

property geom_end: int#: The end index of the link’s collision geometries in the RigidSolver.

property n_cells#: Number of sdf cells of all the link’s geoms.

property n_verts: int#: Number of vertices of all the link’s geoms.

property n_faces: int#: Number of faces of all the link’s geoms.

property n_edges: int#: Number of edges of all the link’s geoms.

property is_free#

RigidLink#

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