flatten-usd

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Flatten a composed USD stage into a single self-contained USD layer using the wu CLI. Use when the user wants to flatten a USD file, resolve sublayers, references, payloads, and inherits, merge USD composition into one file, or prepare a scene for sharing or rendering.

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Flatten USD

Flatten a composed USD stage with wu flatten-usd.

When to Use

Use when the user wants a composed USD layer written as one self-contained .usd, .usda, or .usdc file.
Use when sublayers, references, payloads, or inherits need to be resolved for sharing, debugging, or rendering.
Use before sending a composed stage to tooling that cannot resolve the original dependency chain.
Use render-usd when the user wants images, and print-usd when they only need inspection.

Limitations

The CLI accepts .usd, .usda, and .usdc inputs and outputs. It does not accept .usdz sources or write .usdz.
Flattening changes composition structure. It is useful for handoff, but not a substitute for preserving an editable layered asset.
Large composed stages can produce large outputs and may take a minute or more.
Existing destination files are not overwritten unless --force is set.

Prerequisites

Activate the repo Python environment and confirm wu is on PATH.
Ensure USD Python bindings are installed.
Confirm the source file exists and the destination directory is writable.

Instructions

Confirm the source extension is .usd, .usda, or .usdc.
Choose a destination path, or omit it to use <source>_flat.<ext>.
If the destination exists, ask before using --force.
Run with --verbose when the user needs stage details.
Verify the output exists and report its path.

Command Reference

wu flatten-usd <source.usd> [destination.usd] [OPTIONS]

Option	Description
`--force`, `-f`	Overwrite destination if it already exists.
`--verbose`, `-v`	Print additional stage and export information.

Common Workflows

# Flatten to <stem>_flat.<ext>.
wu flatten-usd scene.usd

# Flatten to a specific ASCII USD output.
wu flatten-usd scene.usd scene_flat.usda

# Overwrite an existing destination after the user confirms.
wu flatten-usd scene.usd scene_flat.usd --force

# Show additional details.
wu flatten-usd scene.usd --verbose

Output Format

Report:

Source path and destination path.
Whether the destination was defaulted or explicit.
Whether --force was used.
Output file size when available.
Any warning that did not block export, such as non-standard Kit metadata that cannot transfer during flatten.
Any failure cause, including missing source, unsupported extension, existing destination, or export failure.

Troubleshooting

Symptom	Cause	Fix
Unsupported extension	Source or destination is not `.usd`, `.usda`, or `.usdc`.	Choose a supported USD layer extension.
Destination already exists	The command refuses to overwrite by default.	Ask the user before rerunning with `--force`.
USD bindings missing	The active environment lacks `pxr`.	Activate the repo environment and install the USD extra if needed.
Large output	Flattening inlined the composed dependency chain.	Keep the layered source asset for editing and use the flat file for handoff.
Metadata warnings	Kit-authored custom metadata may not copy to the flattened layer.	Treat harmless `_CopyMetadata` warnings as informational unless export fails.