# Copyright (c) 2022-2024, The ORBIT Project Developers.
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause
"""Sub-module with USD-related utilities."""
from __future__ import annotations
import functools
import inspect
import re
from collections.abc import Callable
from typing import TYPE_CHECKING, Any
import carb
import omni.isaac.core.utils.stage as stage_utils
import omni.kit.commands
from omni.isaac.cloner import Cloner
from pxr import PhysxSchema, Sdf, Semantics, Usd, UsdGeom, UsdPhysics, UsdShade
from omni.isaac.orbit.utils.string import to_camel_case
from . import schemas
if TYPE_CHECKING:
from .spawners.spawner_cfg import SpawnerCfg
"""
Attribute - Setters.
"""
[docs]def safe_set_attribute_on_usd_schema(schema_api: Usd.APISchemaBase, name: str, value: Any, camel_case: bool):
"""Set the value of an attribute on its USD schema if it exists.
A USD API schema serves as an interface or API for authoring and extracting a set of attributes.
They typically derive from the :class:`pxr.Usd.SchemaBase` class. This function checks if the
attribute exists on the schema and sets the value of the attribute if it exists.
Args:
schema_api: The USD schema to set the attribute on.
name: The name of the attribute.
value: The value to set the attribute to.
camel_case: Whether to convert the attribute name to camel case.
Raises:
TypeError: When the input attribute name does not exist on the provided schema API.
"""
# if value is None, do nothing
if value is None:
return
# convert attribute name to camel case
if camel_case:
attr_name = to_camel_case(name, to="CC")
else:
attr_name = name
# retrieve the attribute
# reference: https://openusd.org/dev/api/_usd__page__common_idioms.html#Usd_Create_Or_Get_Property
attr = getattr(schema_api, f"Create{attr_name}Attr", None)
# check if attribute exists
if attr is not None:
attr().Set(value)
else:
# think: do we ever need to create the attribute if it doesn't exist?
# currently, we are not doing this since the schemas are already created with some defaults.
carb.log_error(f"Attribute '{attr_name}' does not exist on prim '{schema_api.GetPath()}'.")
raise TypeError(f"Attribute '{attr_name}' does not exist on prim '{schema_api.GetPath()}'.")
[docs]def safe_set_attribute_on_usd_prim(prim: Usd.Prim, attr_name: str, value: Any, camel_case: bool):
"""Set the value of a attribute on its USD prim.
The function creates a new attribute if it does not exist on the prim. This is because in some cases (such
as with shaders), their attributes are not exposed as USD prim properties that can be altered. This function
allows us to set the value of the attributes in these cases.
Args:
prim: The USD prim to set the attribute on.
attr_name: The name of the attribute.
value: The value to set the attribute to.
camel_case: Whether to convert the attribute name to camel case.
"""
# if value is None, do nothing
if value is None:
return
# convert attribute name to camel case
if camel_case:
attr_name = to_camel_case(attr_name, to="cC")
# resolve sdf type based on value
if isinstance(value, bool):
sdf_type = Sdf.ValueTypeNames.Bool
elif isinstance(value, int):
sdf_type = Sdf.ValueTypeNames.Int
elif isinstance(value, float):
sdf_type = Sdf.ValueTypeNames.Float
elif isinstance(value, (tuple, list)) and len(value) == 3 and any(isinstance(v, float) for v in value):
sdf_type = Sdf.ValueTypeNames.Float3
elif isinstance(value, (tuple, list)) and len(value) == 2 and any(isinstance(v, float) for v in value):
sdf_type = Sdf.ValueTypeNames.Float2
else:
raise NotImplementedError(
f"Cannot set attribute '{attr_name}' with value '{value}'. Please modify the code to support this type."
)
# change property
omni.kit.commands.execute(
"ChangePropertyCommand",
prop_path=Sdf.Path(f"{prim.GetPath()}.{attr_name}"),
value=value,
prev=None,
type_to_create_if_not_exist=sdf_type,
usd_context_name=prim.GetStage(),
)
"""
Decorators.
"""
[docs]def apply_nested(func: Callable) -> Callable:
"""Decorator to apply a function to all prims under a specified prim-path.
The function iterates over the provided prim path and all its children to apply input function
to all prims under the specified prim path.
If the function succeeds to apply to a prim, it will not look at the children of that prim.
This is based on the physics behavior that nested schemas are not allowed. For example, a parent prim
and its child prim cannot both have a rigid-body schema applied on them, or it is not possible to
have nested articulations.
While traversing the prims under the specified prim path, the function will throw a warning if it
does not succeed to apply the function to any prim. This is because the user may have intended to
apply the function to a prim that does not have valid attributes, or the prim may be an instanced prim.
Args:
func: The function to apply to all prims under a specified prim-path. The function
must take the prim-path and other arguments. It should return a boolean indicating whether
the function succeeded or not.
Returns:
The wrapped function that applies the function to all prims under a specified prim-path.
Raises:
ValueError: If the prim-path does not exist on the stage.
"""
@functools.wraps(func)
def wrapper(prim_path: str | Sdf.Path, *args, **kwargs):
# map args and kwargs to function signature so we can get the stage
# note: we do this to check if stage is given in arg or kwarg
sig = inspect.signature(func)
bound_args = sig.bind(prim_path, *args, **kwargs)
# get current stage
stage = bound_args.arguments.get("stage")
if stage is None:
stage = stage_utils.get_current_stage()
# get USD prim
prim: Usd.Prim = stage.GetPrimAtPath(prim_path)
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# add iterable to check if property was applied on any of the prims
count_success = 0
instanced_prim_paths = []
# iterate over all prims under prim-path
all_prims = [prim]
while len(all_prims) > 0:
# get current prim
child_prim = all_prims.pop(0)
child_prim_path = child_prim.GetPath().pathString # type: ignore
# check if prim is a prototype
if child_prim.IsInstance():
instanced_prim_paths.append(child_prim_path)
continue
# set properties
success = func(child_prim_path, *args, **kwargs)
# if successful, do not look at children
# this is based on the physics behavior that nested schemas are not allowed
if not success:
all_prims += child_prim.GetChildren()
else:
count_success += 1
# check if we were successful in applying the function to any prim
if count_success == 0:
carb.log_warn(
f"Could not perform '{func.__name__}' on any prims under: '{prim_path}'."
" This might be because of the following reasons:"
"\n\t(1) The desired attribute does not exist on any of the prims."
"\n\t(2) The desired attribute exists on an instanced prim."
f"\n\t\tDiscovered list of instanced prim paths: {instanced_prim_paths}"
)
return wrapper
[docs]def clone(func: Callable) -> Callable:
"""Decorator for cloning a prim based on matching prim paths of the prim's parent.
The decorator checks if the parent prim path matches any prim paths in the stage. If so, it clones the
spawned prim at each matching prim path. For example, if the input prim path is: ``/World/Table_[0-9]/Bottle``,
the decorator will clone the prim at each matching prim path of the parent prim: ``/World/Table_0/Bottle``,
``/World/Table_1/Bottle``, etc.
Note:
For matching prim paths, the decorator assumes that valid prims exist for all matching prim paths.
In case no matching prim paths are found, the decorator raises a ``RuntimeError``.
Args:
func: The function to decorate.
Returns:
The decorated function that spawns the prim and clones it at each matching prim path.
It returns the spawned source prim, i.e., the first prim in the list of matching prim paths.
"""
@functools.wraps(func)
def wrapper(prim_path: str | Sdf.Path, cfg: SpawnerCfg, *args, **kwargs):
# cast prim_path to str type in case its an Sdf.Path
prim_path = str(prim_path)
# check prim path is global
if not prim_path.startswith("/"):
raise ValueError(f"Prim path '{prim_path}' is not global. It must start with '/'.")
# resolve: {SPAWN_NS}/AssetName
# note: this assumes that the spawn namespace already exists in the stage
root_path, asset_path = prim_path.rsplit("/", 1)
# check if input is a regex expression
# note: a valid prim path can only contain alphanumeric characters, underscores, and forward slashes
is_regex_expression = re.match(r"^[a-zA-Z0-9/_]+$", root_path) is None
# resolve matching prims for source prim path expression
if is_regex_expression and root_path != "":
source_prim_paths = find_matching_prim_paths(root_path)
# if no matching prims are found, raise an error
if len(source_prim_paths) == 0:
raise RuntimeError(
f"Unable to find source prim path: '{root_path}'. Please create the prim before spawning."
)
else:
source_prim_paths = [root_path]
# resolve prim paths for spawning and cloning
prim_paths = [f"{source_prim_path}/{asset_path}" for source_prim_path in source_prim_paths]
# spawn single instance
prim = func(prim_paths[0], cfg, *args, **kwargs)
# set the prim visibility
if hasattr(cfg, "visible"):
imageable = UsdGeom.Imageable(prim)
if cfg.visible:
imageable.MakeVisible()
else:
imageable.MakeInvisible()
# set the semantic annotations
if hasattr(cfg, "semantic_tags") and cfg.semantic_tags is not None:
# note: taken from replicator scripts.utils.utils.py
for semantic_type, semantic_value in cfg.semantic_tags:
# deal with spaces by replacing them with underscores
semantic_type_sanitized = semantic_type.replace(" ", "_")
semantic_value_sanitized = semantic_value.replace(" ", "_")
# set the semantic API for the instance
instance_name = f"{semantic_type_sanitized}_{semantic_value_sanitized}"
sem = Semantics.SemanticsAPI.Apply(prim, instance_name)
# create semantic type and data attributes
sem.CreateSemanticTypeAttr()
sem.CreateSemanticDataAttr()
sem.GetSemanticTypeAttr().Set(semantic_type)
sem.GetSemanticDataAttr().Set(semantic_value)
# activate rigid body contact sensors
if hasattr(cfg, "activate_contact_sensors") and cfg.activate_contact_sensors:
schemas.activate_contact_sensors(prim_paths[0], cfg.activate_contact_sensors)
# clone asset using cloner API
if len(prim_paths) > 1:
cloner = Cloner()
# clone the prim
cloner.clone(prim_paths[0], prim_paths[1:], replicate_physics=False, copy_from_source=cfg.copy_from_source)
# return the source prim
return prim
return wrapper
"""
Material bindings.
"""
[docs]@apply_nested
def bind_visual_material(
prim_path: str | Sdf.Path,
material_path: str | Sdf.Path,
stage: Usd.Stage | None = None,
stronger_than_descendants: bool = True,
):
"""Bind a visual material to a prim.
This function is a wrapper around the USD command `BindMaterialCommand`_.
.. note::
The function is decorated with :meth:`apply_nested` to allow applying the function to a prim path
and all its descendants.
.. _BindMaterialCommand: https://docs.omniverse.nvidia.com/kit/docs/omni.usd/latest/omni.usd.commands/omni.usd.commands.BindMaterialCommand.html
Args:
prim_path: The prim path where to apply the material.
material_path: The prim path of the material to apply.
stage: The stage where the prim and material exist.
Defaults to None, in which case the current stage is used.
stronger_than_descendants: Whether the material should override the material of its descendants.
Defaults to True.
Raises:
ValueError: If the provided prim paths do not exist on stage.
"""
# resolve stage
if stage is None:
stage = stage_utils.get_current_stage()
# check if prim and material exists
if not stage.GetPrimAtPath(prim_path).IsValid():
raise ValueError(f"Target prim '{material_path}' does not exist.")
if not stage.GetPrimAtPath(material_path).IsValid():
raise ValueError(f"Visual material '{material_path}' does not exist.")
# resolve token for weaker than descendants
if stronger_than_descendants:
binding_strength = "strongerThanDescendants"
else:
binding_strength = "weakerThanDescendants"
# obtain material binding API
# note: we prefer using the command here as it is more robust than the USD API
success, _ = omni.kit.commands.execute(
"BindMaterialCommand",
prim_path=prim_path,
material_path=material_path,
strength=binding_strength,
stage=stage,
)
# return success
return success
[docs]@apply_nested
def bind_physics_material(
prim_path: str | Sdf.Path,
material_path: str | Sdf.Path,
stage: Usd.Stage | None = None,
stronger_than_descendants: bool = True,
):
"""Bind a physics material to a prim.
`Physics material`_ can be applied only to a prim with physics-enabled on them. This includes having
collision APIs, or deformable body APIs, or being a particle system. In case the prim does not have
any of these APIs, the function will not apply the material and return False.
.. note::
The function is decorated with :meth:`apply_nested` to allow applying the function to a prim path
and all its descendants.
.. _Physics material: https://docs.omniverse.nvidia.com/extensions/latest/ext_physics/simulation-control/physics-settings.html#physics-materials
Args:
prim_path: The prim path where to apply the material.
material_path: The prim path of the material to apply.
stage: The stage where the prim and material exist.
Defaults to None, in which case the current stage is used.
stronger_than_descendants: Whether the material should override the material of its descendants.
Defaults to True.
Raises:
ValueError: If the provided prim paths do not exist on stage.
"""
# resolve stage
if stage is None:
stage = stage_utils.get_current_stage()
# check if prim and material exists
if not stage.GetPrimAtPath(prim_path).IsValid():
raise ValueError(f"Target prim '{material_path}' does not exist.")
if not stage.GetPrimAtPath(material_path).IsValid():
raise ValueError(f"Physics material '{material_path}' does not exist.")
# get USD prim
prim = stage.GetPrimAtPath(prim_path)
# check if prim has collision applied on it
has_physics_scene_api = prim.HasAPI(PhysxSchema.PhysxSceneAPI)
has_collider = prim.HasAPI(UsdPhysics.CollisionAPI)
has_deformable_body = prim.HasAPI(PhysxSchema.PhysxDeformableBodyAPI)
has_particle_system = prim.IsA(PhysxSchema.PhysxParticleSystem)
if not (has_physics_scene_api or has_collider or has_deformable_body or has_particle_system):
carb.log_verbose(
f"Cannot apply physics material '{material_path}' on prim '{prim_path}'. It is neither a"
" PhysX scene, collider, a deformable body, nor a particle system."
)
return False
# obtain material binding API
if prim.HasAPI(UsdShade.MaterialBindingAPI):
material_binding_api = UsdShade.MaterialBindingAPI(prim)
else:
material_binding_api = UsdShade.MaterialBindingAPI.Apply(prim)
# obtain the material prim
material = UsdShade.Material(stage.GetPrimAtPath(material_path))
# resolve token for weaker than descendants
if stronger_than_descendants:
binding_strength = UsdShade.Tokens.strongerThanDescendants
else:
binding_strength = UsdShade.Tokens.weakerThanDescendants
# apply the material
material_binding_api.Bind(material, bindingStrength=binding_strength, materialPurpose="physics") # type: ignore
# return success
return True
"""
Exporting.
"""
[docs]def export_prim_to_file(
path: str | Sdf.Path,
source_prim_path: str | Sdf.Path,
target_prim_path: str | Sdf.Path | None = None,
stage: Usd.Stage | None = None,
):
"""Exports a prim from a given stage to a USD file.
The function creates a new layer at the provided path and copies the prim to the layer.
It sets the copied prim as the default prim in the target layer. Additionally, it updates
the stage up-axis and meters-per-unit to match the current stage.
Args:
path: The filepath path to export the prim to.
source_prim_path: The prim path to export.
target_prim_path: The prim path to set as the default prim in the target layer.
Defaults to None, in which case the source prim path is used.
stage: The stage where the prim exists. Defaults to None, in which case the
current stage is used.
Raises:
ValueError: If the prim paths are not global (i.e: do not start with '/').
"""
# automatically casting to str in case args
# are path types
path = str(path)
source_prim_path = str(source_prim_path)
if target_prim_path is not None:
target_prim_path = str(target_prim_path)
if not source_prim_path.startswith("/"):
raise ValueError(f"Source prim path '{source_prim_path}' is not global. It must start with '/'.")
if target_prim_path is not None and not target_prim_path.startswith("/"):
raise ValueError(f"Target prim path '{target_prim_path}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage: Usd.Stage = omni.usd.get_context().get_stage()
# get root layer
source_layer = stage.GetRootLayer()
# only create a new layer if it doesn't exist already
target_layer = Sdf.Find(path)
if target_layer is None:
target_layer = Sdf.Layer.CreateNew(path)
# open the target stage
target_stage = Usd.Stage.Open(target_layer)
# update stage data
UsdGeom.SetStageUpAxis(target_stage, UsdGeom.GetStageUpAxis(stage))
UsdGeom.SetStageMetersPerUnit(target_stage, UsdGeom.GetStageMetersPerUnit(stage))
# specify the prim to copy
source_prim_path = Sdf.Path(source_prim_path)
if target_prim_path is None:
target_prim_path = source_prim_path
# copy the prim
Sdf.CreatePrimInLayer(target_layer, target_prim_path)
Sdf.CopySpec(source_layer, source_prim_path, target_layer, target_prim_path)
# set the default prim
target_layer.defaultPrim = Sdf.Path(target_prim_path).name
# resolve all paths relative to layer path
omni.usd.resolve_paths(source_layer.identifier, target_layer.identifier)
# save the stage
target_layer.Save()
"""
USD Prim properties.
"""
[docs]def make_uninstanceable(prim_path: str | Sdf.Path, stage: Usd.Stage | None = None):
"""Check if a prim and its descendants are instanced and make them uninstanceable.
This function checks if the prim at the specified prim path and its descendants are instanced.
If so, it makes the respective prim uninstanceable by disabling instancing on the prim.
This is useful when we want to modify the properties of a prim that is instanced. For example, if we
want to apply a different material on an instanced prim, we need to make the prim uninstanceable first.
Args:
prim_path: The prim path to check.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# make paths str type if they aren't already
prim_path = str(prim_path)
# check if prim path is global
if not prim_path.startswith("/"):
raise ValueError(f"Prim path '{prim_path}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# get prim
prim: Usd.Prim = stage.GetPrimAtPath(prim_path)
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# iterate over all prims under prim-path
all_prims = [prim]
while len(all_prims) > 0:
# get current prim
child_prim = all_prims.pop(0)
# check if prim is instanced
if child_prim.IsInstance():
# make the prim uninstanceable
child_prim.SetInstanceable(False)
# add children to list
all_prims += child_prim.GetChildren()
"""
USD Stage traversal.
"""
[docs]def get_first_matching_child_prim(
prim_path: str | Sdf.Path, predicate: Callable[[Usd.Prim], bool], stage: Usd.Stage | None = None
) -> Usd.Prim | None:
"""Recursively get the first USD Prim at the path string that passes the predicate function
Args:
prim_path: The path of the prim in the stage.
predicate: The function to test the prims against. It takes a prim as input and returns a boolean.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
The first prim on the path that passes the predicate. If no prim passes the predicate, it returns None.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# make paths str type if they aren't already
prim_path = str(prim_path)
# check if prim path is global
if not prim_path.startswith("/"):
raise ValueError(f"Prim path '{prim_path}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# get prim
prim = stage.GetPrimAtPath(prim_path)
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# iterate over all prims under prim-path
all_prims = [prim]
while len(all_prims) > 0:
# get current prim
child_prim = all_prims.pop(0)
# check if prim passes predicate
if predicate(child_prim):
return child_prim
# add children to list
all_prims += child_prim.GetChildren()
return None
[docs]def get_all_matching_child_prims(
prim_path: str | Sdf.Path,
predicate: Callable[[Usd.Prim], bool] = lambda _: True,
depth: int | None = None,
stage: Usd.Stage | None = None,
) -> list[Usd.Prim]:
"""Performs a search starting from the root and returns all the prims matching the predicate.
Args:
prim_path: The root prim path to start the search from.
predicate: The predicate that checks if the prim matches the desired criteria. It takes a prim as input
and returns a boolean. Defaults to a function that always returns True.
depth: The maximum depth for traversal, should be bigger than zero if specified.
Defaults to None (i.e: traversal happens till the end of the tree).
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
A list containing all the prims matching the predicate.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# make paths str type if they aren't already
prim_path = str(prim_path)
# check if prim path is global
if not prim_path.startswith("/"):
raise ValueError(f"Prim path '{prim_path}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# get prim
prim = stage.GetPrimAtPath(prim_path)
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# check if depth is valid
if depth is not None and depth <= 0:
raise ValueError(f"Depth must be bigger than zero, got {depth}.")
# iterate over all prims under prim-path
# list of tuples (prim, current_depth)
all_prims_queue = [(prim, 0)]
output_prims = []
while len(all_prims_queue) > 0:
# get current prim
child_prim, current_depth = all_prims_queue.pop(0)
# check if prim passes predicate
if predicate(child_prim):
output_prims.append(child_prim)
# add children to list
if depth is None or current_depth < depth:
all_prims_queue += [(child, current_depth + 1) for child in child_prim.GetChildren()]
return output_prims
[docs]def find_first_matching_prim(prim_path_regex: str, stage: Usd.Stage | None = None) -> Usd.Prim | None:
"""Find the first matching prim in the stage based on input regex expression.
Args:
prim_path_regex: The regex expression for prim path.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
The first prim that matches input expression. If no prim matches, returns None.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# check prim path is global
if not prim_path_regex.startswith("/"):
raise ValueError(f"Prim path '{prim_path_regex}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# need to wrap the token patterns in '^' and '$' to prevent matching anywhere in the string
pattern = f"^{prim_path_regex}$"
compiled_pattern = re.compile(pattern)
# obtain matching prim (depth-first search)
for prim in stage.Traverse():
# check if prim passes predicate
if compiled_pattern.match(prim.GetPath().pathString) is not None:
return prim
return None
[docs]def find_matching_prims(prim_path_regex: str, stage: Usd.Stage | None = None) -> list[Usd.Prim]:
"""Find all the matching prims in the stage based on input regex expression.
Args:
prim_path_regex: The regex expression for prim path.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
A list of prims that match input expression.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# check prim path is global
if not prim_path_regex.startswith("/"):
raise ValueError(f"Prim path '{prim_path_regex}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# need to wrap the token patterns in '^' and '$' to prevent matching anywhere in the string
tokens = prim_path_regex.split("/")[1:]
tokens = [f"^{token}$" for token in tokens]
# iterate over all prims in stage (breath-first search)
all_prims = [stage.GetPseudoRoot()]
output_prims = []
for index, token in enumerate(tokens):
token_compiled = re.compile(token)
for prim in all_prims:
for child in prim.GetAllChildren():
if token_compiled.match(child.GetName()) is not None:
output_prims.append(child)
if index < len(tokens) - 1:
all_prims = output_prims
output_prims = []
return output_prims
[docs]def find_matching_prim_paths(prim_path_regex: str, stage: Usd.Stage | None = None) -> list[str]:
"""Find all the matching prim paths in the stage based on input regex expression.
Args:
prim_path_regex: The regex expression for prim path.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
A list of prim paths that match input expression.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
"""
# obtain matching prims
output_prims = find_matching_prims(prim_path_regex, stage)
# convert prims to prim paths
output_prim_paths = []
for prim in output_prims:
output_prim_paths.append(prim.GetPath().pathString)
return output_prim_paths
[docs]def find_global_fixed_joint_prim(
prim_path: str | Sdf.Path, check_enabled_only: bool = False, stage: Usd.Stage | None = None
) -> UsdPhysics.Joint | None:
"""Find the fixed joint prim under the specified prim path that connects the target to the simulation world.
A joint is a connection between two bodies. A fixed joint is a joint that does not allow relative motion
between the two bodies. When a fixed joint has only one target body, it is considered to attach the body
to the simulation world.
This function finds the fixed joint prim that has only one target under the specified prim path. If no such
fixed joint prim exists, it returns None.
Args:
prim_path: The prim path to search for the fixed joint prim.
check_enabled_only: Whether to consider only enabled fixed joints. Defaults to False.
If False, then all joints (enabled or disabled) are considered.
stage: The stage where the prim exists. Defaults to None, in which case the current stage is used.
Returns:
The fixed joint prim that has only one target. If no such fixed joint prim exists, it returns None.
Raises:
ValueError: If the prim path is not global (i.e: does not start with '/').
ValueError: If the prim path does not exist on the stage.
"""
# check prim path is global
if not prim_path.startswith("/"):
raise ValueError(f"Prim path '{prim_path}' is not global. It must start with '/'.")
# get current stage
if stage is None:
stage = stage_utils.get_current_stage()
# check if prim exists
prim = stage.GetPrimAtPath(prim_path)
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
fixed_joint_prim = None
# we check all joints under the root prim and classify the asset as fixed base if there exists
# a fixed joint that has only one target (i.e. the root link).
for prim in Usd.PrimRange(prim):
# note: ideally checking if it is FixedJoint would have been enough, but some assets use "Joint" as the
# schema name which makes it difficult to distinguish between the two.
joint_prim = UsdPhysics.Joint(prim)
if joint_prim:
# if check_enabled_only is True, we only consider enabled joints
if check_enabled_only and not joint_prim.GetJointEnabledAttr().Get():
continue
# check body 0 and body 1 exist
body_0_exist = joint_prim.GetBody0Rel().GetTargets() != []
body_1_exist = joint_prim.GetBody1Rel().GetTargets() != []
# if either body 0 or body 1 does not exist, we have a fixed joint that connects to the world
if not (body_0_exist and body_1_exist):
fixed_joint_prim = joint_prim
break
return fixed_joint_prim
