usd-editor

name	usd-editor
description	Guide for modifying USD ASCII (.usda) files, including prims, properties, composition arcs, variants, and transforms. Use when editing or reviewing .usda files by hand.

USD Editor

Quick Start

Use this skill for minimal, text-level USD or USDA edits. Keep the change small and preserve existing composition unless the task explicitly says otherwise.

When authored Reality Composer Pro or USD content owns the scene, geometry, transform, animation, or material, keep that authored surface as the source of truth. Use Swift and RealityKit to load or adjust runtime state; do not recreate authored USD content in Swift unless the request is explicitly procedural.

If the change is material- or shader-specific for RealityKit, prefer shadergraph-editor.

Load References When

Reference	When to Use
usd-syntax	When you need a refresher on .usda syntax, values, and path formats.
prims-properties	When adding or editing prims, attributes, or relationships.
composition-variants	When touching sublayers, references, payloads, or variant sets.
transforms-units	When editing transforms, xformOps, or stage units and up-axis metadata.
time-samples	When modifying animated or time-sampled properties.
command-line-tools	When you need a quick reference for common USD command-line tools.
usdcat	When converting, flattening, or inspecting USD files.
usdchecker	When validating USD or USDZ assets, including RealityKit-focused checks.
usdrecord	When rendering images from USD files.
usdtree	When inspecting the prim hierarchy of a USD file.
usdzip	When creating or inspecting USDZ packages.
usdedit	When you need the official text-editing workflow for a USD-readable file.
visionos-runtime-loading.md	When the question is how the authored USD or USDZ actually loads and behaves in a visionOS app.
apple-runtime-boundaries.md	When deciding whether to edit authored USD / Reality Composer Pro content, load it through RealityKit, or validate it for Apple platforms.

Workflow

1. Identify the owner: authored USD / Reality Composer Pro asset, package resource, or runtime-only Swift-generated content.
2. Inspect the stage with usdtree, usdcat --loadOnly, or usdcat --flatten before editing, depending on the risk.
3. Locate the exact prim path and layer that owns the opinion.
4. Choose over, def, or a list edit deliberately.
5. Apply the minimum change needed.
6. Re-check paths, transforms, or composition edges that were touched.
7. Run the narrowest validation tool that matches the change, then run usdchecker --arkit for shipping visionOS USDZ assets.

Guardrails

• Do not replace a prim with def when over is the correct edit.
• Avoid composition-arc changes unless they are explicitly requested.
• If a RealityKit app loads the asset with Entity(named:in:), Entity(contentsOf:withName:), or a generated Reality Composer Pro content bundle, prefer fixing the authored asset and validating the bundle/package over building a parallel Swift scene graph.
• Do not hand-edit a .usdz package in place; inspect or unpack it, edit the source layer, rebuild the package, and validate the result.
• Validate final Apple-platform USDZ output with usdchecker --arkit --strict, not just a source-layer parse check.
• Preserve existing formatting and comments when possible.

Output Expectations

Provide:

• the prim or path edited
• which reference files were used
• the exact class of USD change made
• the validation step used
• routing to shadergraph-editor or runtime testing if needed