# Copyright (c) 2022-2025, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause
"""Utilities for creating and manipulating USD prims."""
from __future__ import annotations
import functools
import inspect
import logging
import re
from collections.abc import Callable, Sequence
from typing import TYPE_CHECKING, Any
import omni
import omni.kit.commands
import omni.usd
import usdrt # noqa: F401
from isaacsim.core.cloner import Cloner
from omni.usd.commands import DeletePrimsCommand, MovePrimCommand
from pxr import PhysxSchema, Sdf, Usd, UsdGeom, UsdPhysics, UsdShade
from isaaclab.utils.string import to_camel_case
from isaaclab.utils.version import get_isaac_sim_version
from .queries import find_matching_prim_paths
from .semantics import add_labels
from .stage import attach_stage_to_usd_context, get_current_stage, get_current_stage_id
if TYPE_CHECKING:
from isaaclab.sim.spawners.spawner_cfg import SpawnerCfg
# import logger
logger = logging.getLogger(__name__)
"""
General Utils
"""
[docs]def create_prim(
prim_path: str,
prim_type: str = "Xform",
position: Sequence[float] | None = None,
translation: Sequence[float] | None = None,
orientation: Sequence[float] | None = None,
scale: Sequence[float] | None = None,
usd_path: str | None = None,
semantic_label: str | None = None,
semantic_type: str = "class",
attributes: dict | None = None,
stage: Usd.Stage | None = None,
) -> Usd.Prim:
"""Creates a prim in the provided USD stage.
The method applies the specified transforms, the semantic label and sets the specified attributes.
Args:
prim_path: The path of the new prim.
prim_type: Prim type name
position: prim position (applied last)
translation: prim translation (applied last)
orientation: prim rotation as quaternion
scale: scaling factor in x, y, z.
usd_path: Path to the USD that this prim will reference.
semantic_label: Semantic label.
semantic_type: set to "class" unless otherwise specified.
attributes: Key-value pairs of prim attributes to set.
stage: The stage to create the prim in. Defaults to None, in which case the current stage is used.
Returns:
The created USD prim.
Raises:
ValueError: If there is already a prim at the provided prim_path.
Example:
>>> import isaaclab.sim as sim_utils
>>>
>>> # create a cube (/World/Cube) of size 2 centered at (1.0, 0.5, 0.0)
>>> sim_utils.create_prim(
... prim_path="/World/Cube",
... prim_type="Cube",
... position=(1.0, 0.5, 0.0),
... attributes={"size": 2.0}
... )
Usd.Prim(</World/Cube>)
"""
# Note: Imported here to prevent cyclic dependency in the module.
from isaacsim.core.prims import XFormPrim
# obtain stage handle
stage = get_current_stage() if stage is None else stage
# check if prim already exists
if stage.GetPrimAtPath(prim_path).IsValid():
raise ValueError(f"A prim already exists at path: '{prim_path}'.")
# create prim in stage
prim = stage.DefinePrim(prim_path, prim_type)
if not prim.IsValid():
raise ValueError(f"Failed to create prim at path: '{prim_path}' of type: '{prim_type}'.")
# apply attributes into prim
if attributes is not None:
for k, v in attributes.items():
prim.GetAttribute(k).Set(v)
# add reference to USD file
if usd_path is not None:
add_usd_reference(prim_path=prim_path, usd_path=usd_path, stage=stage)
# add semantic label to prim
if semantic_label is not None:
add_labels(prim, labels=[semantic_label], instance_name=semantic_type)
# apply the transformations
from isaacsim.core.api.simulation_context.simulation_context import SimulationContext
if SimulationContext.instance() is None:
# FIXME: remove this, we should never even use backend utils especially not numpy ones
import isaacsim.core.utils.numpy as backend_utils
device = "cpu"
else:
backend_utils = SimulationContext.instance().backend_utils
device = SimulationContext.instance().device
if position is not None:
position = backend_utils.expand_dims(backend_utils.convert(position, device), 0)
if translation is not None:
translation = backend_utils.expand_dims(backend_utils.convert(translation, device), 0)
if orientation is not None:
orientation = backend_utils.expand_dims(backend_utils.convert(orientation, device), 0)
if scale is not None:
scale = backend_utils.expand_dims(backend_utils.convert(scale, device), 0)
XFormPrim(prim_path, positions=position, translations=translation, orientations=orientation, scales=scale)
return prim
[docs]def delete_prim(prim_path: str | Sequence[str], stage: Usd.Stage | None = None) -> None:
"""Removes the USD Prim and its descendants from the scene if able.
Args:
prim_path: The path of the prim to delete. If a list of paths is provided,
the function will delete all the prims in the list.
stage: The stage to delete the prim in. Defaults to None, in which case the current stage is used.
Example:
>>> import isaaclab.sim as sim_utils
>>>
>>> sim_utils.delete_prim("/World/Cube")
"""
# convert prim_path to list if it is a string
if isinstance(prim_path, str):
prim_path = [prim_path]
# get stage handle
stage = get_current_stage() if stage is None else stage
# delete prims
DeletePrimsCommand(prim_path, stage=stage).do()
[docs]def move_prim(path_from: str, path_to: str, keep_world_transform: bool = True, stage: Usd.Stage | None = None) -> None:
"""Moves a prim from one path to another within a USD stage.
This function moves the prim from the source path to the destination path. If the :attr:`keep_world_transform`
is set to True, the world transform of the prim is kept. This implies that the prim's local transform is reset
such that the prim's world transform is the same as the source path's world transform. If it is set to False,
the prim's local transform is preserved.
.. warning::
Reparenting or moving prims in USD is an expensive operation that may trigger
significant recomposition costs, especially in large or deeply layered stages.
Args:
path_from: Path of the USD Prim you wish to move
path_to: Final destination of the prim
keep_world_transform: Whether to keep the world transform of the prim. Defaults to True.
stage: The stage to move the prim in. Defaults to None, in which case the current stage is used.
Example:
>>> import isaaclab.sim as sim_utils
>>>
>>> # given the stage: /World/Cube. Move the prim Cube outside the prim World
>>> sim_utils.move_prim("/World/Cube", "/Cube")
"""
# get stage handle
stage = get_current_stage() if stage is None else stage
# move prim
MovePrimCommand(
path_from=path_from, path_to=path_to, keep_world_transform=keep_world_transform, stage_or_context=stage
).do()
"""
USD Prim properties and attributes.
"""
[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 '/').
"""
# get stage handle
if stage is None:
stage = get_current_stage()
# 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 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 is instanced
if child_prim.IsInstance():
# make the prim uninstanceable
child_prim.SetInstanceable(False)
# add children to list
all_prims += child_prim.GetFilteredChildren(Usd.TraverseInstanceProxies())
[docs]def resolve_prim_pose(
prim: Usd.Prim, ref_prim: Usd.Prim | None = None
) -> tuple[tuple[float, float, float], tuple[float, float, float, float]]:
"""Resolve the pose of a prim with respect to another prim.
Note:
This function ignores scale and skew by orthonormalizing the transformation
matrix at the final step. However, if any ancestor prim in the hierarchy
has non-uniform scale, that scale will still affect the resulting position
and orientation of the prim (because it's baked into the transform before
scale removal).
In other words: scale **is not removed hierarchically**. If you need
completely scale-free poses, you must walk the transform chain and strip
scale at each level. Please open an issue if you need this functionality.
Args:
prim: The USD prim to resolve the pose for.
ref_prim: The USD prim to compute the pose with respect to.
Defaults to None, in which case the world frame is used.
Returns:
A tuple containing the position (as a 3D vector) and the quaternion orientation
in the (w, x, y, z) format.
Raises:
ValueError: If the prim or ref prim is not valid.
"""
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim.GetPath().pathString}' is not valid.")
# get prim xform
xform = UsdGeom.Xformable(prim)
prim_tf = xform.ComputeLocalToWorldTransform(Usd.TimeCode.Default())
# sanitize quaternion
# this is needed, otherwise the quaternion might be non-normalized
prim_tf = prim_tf.GetOrthonormalized()
if ref_prim is not None:
# check if ref prim is valid
if not ref_prim.IsValid():
raise ValueError(f"Ref prim at path '{ref_prim.GetPath().pathString}' is not valid.")
# get ref prim xform
ref_xform = UsdGeom.Xformable(ref_prim)
ref_tf = ref_xform.ComputeLocalToWorldTransform(Usd.TimeCode.Default())
# make sure ref tf is orthonormal
ref_tf = ref_tf.GetOrthonormalized()
# compute relative transform to get prim in ref frame
prim_tf = prim_tf * ref_tf.GetInverse()
# extract position and orientation
prim_pos = [*prim_tf.ExtractTranslation()]
prim_quat = [prim_tf.ExtractRotationQuat().real, *prim_tf.ExtractRotationQuat().imaginary]
return tuple(prim_pos), tuple(prim_quat)
[docs]def resolve_prim_scale(prim: Usd.Prim) -> tuple[float, float, float]:
"""Resolve the scale of a prim in the world frame.
At an attribute level, a USD prim's scale is a scaling transformation applied to the prim with
respect to its parent prim. This function resolves the scale of the prim in the world frame,
by computing the local to world transform of the prim. This is equivalent to traversing up
the prim hierarchy and accounting for the rotations and scales of the prims.
For instance, if a prim has a scale of (1, 2, 3) and it is a child of a prim with a scale of (4, 5, 6),
then the scale of the prim in the world frame is (4, 10, 18).
Args:
prim: The USD prim to resolve the scale for.
Returns:
The scale of the prim in the x, y, and z directions in the world frame.
Raises:
ValueError: If the prim is not valid.
"""
# check if prim is valid
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim.GetPath().pathString}' is not valid.")
# compute local to world transform
xform = UsdGeom.Xformable(prim)
world_transform = xform.ComputeLocalToWorldTransform(Usd.TimeCode.Default())
# extract scale
return tuple([*(v.GetLength() for v in world_transform.ExtractRotationMatrix())])
"""
Attribute - Setters.
"""
[docs]def set_prim_visibility(prim: Usd.Prim, visible: bool) -> None:
"""Sets the visibility of the prim in the opened stage.
.. note::
The method does this through the USD API.
Args:
prim: the USD prim
visible: flag to set the visibility of the usd prim in stage.
Example:
>>> import isaaclab.sim as sim_utils
>>>
>>> # given the stage: /World/Cube. Make the Cube not visible
>>> prim = sim_utils.get_prim_at_path("/World/Cube")
>>> sim_utils.set_prim_visibility(prim, False)
"""
imageable = UsdGeom.Imageable(prim)
if visible:
imageable.MakeVisible()
else:
imageable.MakeInvisible()
[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.
logger.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."
)
# early attach stage to usd context if stage is in memory
# since stage in memory is not supported by the "ChangePropertyCommand" kit command
attach_stage_to_usd_context(attaching_early=True)
# 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(),
)
"""
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 '/').
"""
# get stage handle
if stage is None:
stage = get_current_stage()
# 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 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()
"""
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 = 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:
logger.warning(
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):
# get stage handle
stage = get_current_stage()
# 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(" ", "_")
# add labels to the prim
add_labels(
prim, labels=[semantic_value_sanitized], instance_name=semantic_type_sanitized, overwrite=False
)
# activate rigid body contact sensors (lazy import to avoid circular import with schemas)
if hasattr(cfg, "activate_contact_sensors") and cfg.activate_contact_sensors: # type: ignore
from ..schemas import schemas as _schemas
_schemas.activate_contact_sensors(prim_paths[0])
# clone asset using cloner API
if len(prim_paths) > 1:
cloner = Cloner(stage=stage)
# check version of Isaac Sim to determine whether clone_in_fabric is valid
if get_isaac_sim_version().major < 5:
# clone the prim
cloner.clone(
prim_paths[0], prim_paths[1:], replicate_physics=False, copy_from_source=cfg.copy_from_source
)
else:
# clone the prim
clone_in_fabric = kwargs.get("clone_in_fabric", False)
replicate_physics = kwargs.get("replicate_physics", False)
cloner.clone(
prim_paths[0],
prim_paths[1:],
replicate_physics=replicate_physics,
copy_from_source=cfg.copy_from_source,
clone_in_fabric=clone_in_fabric,
)
# 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.
"""
# get stage handle
if stage is None:
stage = 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://isaac-sim.github.io/IsaacLab/main/source/api/lab/isaaclab.sim.html#isaaclab.sim.SimulationCfg.physics_material
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.
"""
# get stage handle
if stage is None:
stage = 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):
logger.debug(
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
"""
USD References and Variants.
"""
[docs]def add_usd_reference(
prim_path: str, usd_path: str, prim_type: str = "Xform", stage: Usd.Stage | None = None
) -> Usd.Prim:
"""Adds a USD reference at the specified prim path on the provided stage.
This function adds a reference to an external USD file at the specified prim path on the provided stage.
If the prim does not exist, it will be created with the specified type.
The function also handles stage units verification to ensure compatibility. For instance,
if the current stage is in meters and the referenced USD file is in centimeters, the function will
convert the units to match. This is done using the :mod:`omni.metrics.assembler` functionality.
Args:
prim_path: The prim path where the reference will be attached.
usd_path: The path to USD file to reference.
prim_type: The type of prim to create if it doesn't exist. Defaults to "Xform".
stage: The stage to add the reference to. Defaults to None, in which case the current stage is used.
Returns:
The USD prim at the specified prim path.
Raises:
FileNotFoundError: When the input USD file is not found at the specified path.
"""
# get current stage
stage = get_current_stage() if stage is None else stage
# get prim at path
prim = stage.GetPrimAtPath(prim_path)
if not prim.IsValid():
prim = stage.DefinePrim(prim_path, prim_type)
def _add_reference_to_prim(prim: Usd.Prim) -> Usd.Prim:
"""Helper function to add a reference to a prim."""
success_bool = prim.GetReferences().AddReference(usd_path)
if not success_bool:
raise RuntimeError(
f"Unable to add USD reference to the prim at path: {prim_path} from the USD file at path: {usd_path}"
)
return prim
# Compatibility with Isaac Sim 4.5 where omni.metrics is not available
if get_isaac_sim_version().major < 5:
return _add_reference_to_prim(prim)
# check if the USD file is valid and add reference to the prim
sdf_layer = Sdf.Layer.FindOrOpen(usd_path)
if not sdf_layer:
raise FileNotFoundError(f"Unable to open the usd file at path: {usd_path}")
# import metrics assembler interface
# note: this is only available in Isaac Sim 5.0 and above
from omni.metrics.assembler.core import get_metrics_assembler_interface
# obtain the stage ID
stage_id = get_current_stage_id()
# check if the layers are compatible (i.e. the same units)
ret_val = get_metrics_assembler_interface().check_layers(
stage.GetRootLayer().identifier, sdf_layer.identifier, stage_id
)
if ret_val["ret_val"]:
try:
import omni.metrics.assembler.ui
omni.kit.commands.execute(
"AddReference", stage=stage, prim_path=prim.GetPath(), reference=Sdf.Reference(usd_path)
)
return prim
except Exception:
return _add_reference_to_prim(prim)
else:
return _add_reference_to_prim(prim)
[docs]def get_usd_references(prim_path: str, stage: Usd.Stage | None = None) -> list[str]:
"""Gets the USD references at the specified prim path on the provided stage.
Args:
prim_path: The prim path to get the USD references from.
stage: The stage to get the USD references from. Defaults to None, in which case the current stage is used.
Returns:
A list of USD reference paths.
"""
# get stage handle
stage = get_current_stage() if stage is None else stage
# get prim at path
prim = stage.GetPrimAtPath(prim_path)
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# get USD references
references = []
for prim_spec in prim.GetPrimStack():
references.extend(prim_spec.referenceList.prependedItems.assetPath)
return references
[docs]def select_usd_variants(prim_path: str, variants: object | dict[str, str], stage: Usd.Stage | None = None):
"""Sets the variant selections from the specified variant sets on a USD prim.
`USD Variants`_ are a very powerful tool in USD composition that allows prims to have different options on
a single asset. This can be done by modifying variations of the same prim parameters per variant option in a set.
This function acts as a script-based utility to set the variant selections for the specified variant sets on a
USD prim.
The function takes a dictionary or a config class mapping variant set names to variant selections. For instance,
if we have a prim at ``"/World/Table"`` with two variant sets: "color" and "size", we can set the variant
selections as follows:
.. code-block:: python
select_usd_variants(
prim_path="/World/Table",
variants={
"color": "red",
"size": "large",
},
)
Alternatively, we can use a config class to define the variant selections:
.. code-block:: python
@configclass
class TableVariants:
color: Literal["blue", "red"] = "red"
size: Literal["small", "large"] = "large"
select_usd_variants(
prim_path="/World/Table",
variants=TableVariants(),
)
Args:
prim_path: The path of the USD prim.
variants: A dictionary or config class mapping variant set names to variant selections.
stage: The USD stage. Defaults to None, in which case, the current stage is used.
Raises:
ValueError: If the prim at the specified path is not valid.
.. _USD Variants: https://graphics.pixar.com/usd/docs/USD-Glossary.html#USDGlossary-Variant
"""
# get stage handle
if stage is None:
stage = get_current_stage()
# Obtain prim
prim = stage.GetPrimAtPath(prim_path)
if not prim.IsValid():
raise ValueError(f"Prim at path '{prim_path}' is not valid.")
# Convert to dict if we have a configclass object.
if not isinstance(variants, dict):
variants = variants.to_dict() # type: ignore
existing_variant_sets = prim.GetVariantSets()
for variant_set_name, variant_selection in variants.items(): # type: ignore
# Check if the variant set exists on the prim.
if not existing_variant_sets.HasVariantSet(variant_set_name):
logger.warning(f"Variant set '{variant_set_name}' does not exist on prim '{prim_path}'.")
continue
variant_set = existing_variant_sets.GetVariantSet(variant_set_name)
# Only set the variant selection if it is different from the current selection.
if variant_set.GetVariantSelection() != variant_selection:
variant_set.SetVariantSelection(variant_selection)
logger.info(
f"Setting variant selection '{variant_selection}' for variant set '{variant_set_name}' on"
f" prim '{prim_path}'."
)
