Usd Editor

Guide for modifying USD ASCII (.usda) files, including prims, properties, composition arcs, variants, and transforms. Use when editing or reviewing .usda fil...

Security Scan

The skill's instructions, files, and requirements are consistent with its stated purpose of guiding safe manual edits to USD ASCII (.usda) files and using official USD tools.

Purpose & Capability

The skill's name/description match the included instructions and reference docs for USD editing. One minor mismatch: the SKILL.md instructs use of USD command-line tools but the skill declares no required binaries — this is reasonable for an instruction-only skill but means the agent will need those tools available at runtime to follow the guidance.

Instruction Scope

Runtime instructions are focused on editing .usda files, preserving composition, and using USD CLI tools. They do not direct reading unrelated system files, exfiltration, or contacting external endpoints.

Install Mechanism

No install spec and no code files — lowest-risk pattern for an instruction-only skill. The skill only contains documentation and examples.

Credentials

No environment variables, credentials, or config paths are requested. The references to USD tools are proportional to the stated task.

Persistence & Privilege

always is false and the skill is user-invocable. It does not request persistent privileges or modify other skills or system settings.

Assessment

This skill appears coherent and instruction-only: it provides guidance and examples for editing .usda files and recommends using official USD CLI tools. Before installing/using it, ensure the USD command-line tools (usdcat, usdedit, usdtree, usdchecker, usdzip, usdrecord, etc.) are available on the agent environment if you expect the agent to run them. Because the skill can be invoked by the agent to edit files, confirm the agent has appropriate file access and that you keep backups or use usdedit --noeffect to preview changes. There are no requests for credentials or external endpoints; nevertheless review any outputs the agent proposes to write and avoid granting the agent unrelated system or network privileges.

Description and Goals

This skill guides safe, minimal edits to USD ASCII (.usda) files and the proper use of official USD command-line tools. It focuses on preserving stage structure, using correct specifiers and property types, and avoiding composition mistakes while making targeted changes.

Goals

• Make precise edits without disrupting existing USD composition
• Preserve file formatting and authoring style
• Use correct prim specifiers, property types, and relationships
• Avoid common USD pitfalls (wrong paths, missing xformOpOrder, broken connections)
• Guide safe manipulation and inspection of USD assets using the command-line tools

What This Skill Should Do

When asked to modify a .usda file, this skill should:

1. Inspect the stage structure - Identify root prims, scopes, and relevant paths.
2. Choose the correct specifier - Use over for edits to existing prims, def for new prims.
3. Edit only what is necessary - Preserve unrelated content and formatting.
4. Respect composition - Avoid changing subLayers, references, or variants unless asked.
5. Validate connections and paths - Ensure SdfPath targets are valid and type-compatible.

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

Quick Start Workflow

1. Locate the prim path you need to edit (search by prim name or SdfPath).
2. Determine whether you should over an existing prim or def a new one.
3. Apply the smallest possible change (attribute value, relationship target, or child prim).
4. If adding transforms, update xformOpOrder to match your new ops.
5. Re-check any paths or connections you touched.

Information About the Skill

Core Concepts

Stage and Layer

A USD stage is composed of one or more layers. A .usda file is a single ASCII layer that can sublayer or reference others.

Prim and Specifier

A prim is a scene graph node. Specifiers control behavior: def creates, over modifies, class defines a reusable template.

Properties

Attributes store typed data; relationships (rel) point to other prims.

Composition Arc

Mechanisms like sublayers, references, and payloads that bring other USD data into the stage.

SdfPath

A path to a prim or property, written like </Root/Child> or </Root/Mat.outputs:surface>.

List Editing

USD list ops (prepend, append, delete, add) modify lists without replacing them.

Variants

Variant sets provide alternative content branches for a prim.

Time Samples

Animated or time-varying data stored in timeSamples dictionaries.

Reference Tables

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/up axis metadata.
time-samples	When modifying animated/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.

Implementation Patterns

Override an Existing Prim

over "Mesh"
{
    token visibility = "invisible"
}

Add a Simple Xform with Translate

def Xform "Pivot"
{
    double3 xformOp:translate = (0.0, 0.1, 0.0)
    uniform token[] xformOpOrder = ["xformOp:translate"]
}

Bind a Material Relationship

rel material:binding = </Materials/Mat>

Pitfalls and Checks

• Don't replace a prim with def when you only need an over.
• Keep xformOpOrder consistent with the ops you add or remove.
• Verify SdfPath targets exist and match the expected property type.
• Avoid editing composition arcs unless explicitly requested.
• Preserve existing formatting and comments to minimize diff noise.