Sam Haves
700da7c5bd
PiperOrigin-RevId: 789365870 Change-Id: I19cce03ec2ffc28cdf4252bfd02c8b5163bb5ba2
88 lines
3.0 KiB
ReStructuredText
88 lines
3.0 KiB
ReStructuredText
File Format Plugin
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=========================
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What is an SdfFileFormat plugin?
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--------------------------------
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In the OpenUSD framework, ``Sdf`` stands for Scene Description Foundations. It's the underlying layer that handles the
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serialization and composition of scene data. A ``SdfFileFormat`` plugin is a component that teaches USD how to read and
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write a specific file format.
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By default, USD comes with plugins for its own formats (``.usda``, ``.usdc``, ``.usdz``) and the community has created
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several plugin extension such as the `Adobe File Format Plugins
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<https://github.com/adobe/USD-Fileformat-plugins/tree/main>`__.
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The MJCF ``SdfFileFormat`` plugin allows USD-aware applications to directly understand and interact with MuJoCo's native
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``.xml`` (MJCF) files as if they were native USD files.
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What does it enable?
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------------------------
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This plugin enables:
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1. **Referencing MJCF files in USD:** Using standard USD composition arcs (like references, payloads) to include an
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MJCF file directly within a larger USD scene. For example, you can place a MuJoCo robot defined in an ``.xml`` file
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into a room scene modeled in USD.
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2. **Load MJCF files in USD tools:** Tools like ``usdview`` or other USD-based
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applications can open, inspect, and render MJCF files, translating the MJCF elements into USD prims and attributes
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on the fly.
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3. **Convert MJCF to USD:** The plugin can be used as a basis for converting MJCF files to persistent
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USD files (e.g., ``.usda`` or ``.usdc``).
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Essentially, it makes MJCF a first-class citizen in the USD ecosystem.
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Usage
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------------------
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1. **Installation:** refer to :doc:`building`.
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2. **Referencing in a USD file (e.g., ``.usda``):**
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.. code-block:: usd
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:caption: example.usda
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#usda 1.0
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(
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upAxis = "Z"
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)
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def Xform "world"
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{
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def "robot" (
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prepend references = @./my_robot.xml@
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)
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{
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}
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}
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In this example, ``my_robot.xml`` is an MJCF file in the same directory. USD will use the plugin to load and
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interpret its contents.
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3. **Opening in usdview:**
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.. code-block:: bash
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usdview my_robot.xml
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If the plugin is correctly set up, ``usdview`` will render the robot defined in the MJCF file.
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4. **Using in Python (with USD API):**
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.. code-block:: python
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from pxr import Usd
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# Load an MJCF file as a USD stage
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stage = Usd.Stage.Open('my_robot.xml')
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if stage:
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print(f"Successfully opened {stage.GetRootLayer().identifier}")
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# You can now inspect the stage as any other USD stage
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for prim in stage.TraverseAll():
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print(prim.GetPath())
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else:
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print("Failed to open MJCF file")
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This plugin significantly enhances the interoperability between MuJoCo and USD-based workflows, allowing
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seamless integration of physics assets defined in MJCF into broader 3D environments.
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