USD (Universal Scene Description) is Pixar's open 3D scene format, now the standard interchange format for VFX pipelines (Houdini, Katana, Clarisse), real-time engines (Omniverse), and Apple's AR platform (Reality Composer, ARKit). If you're working with 3D assets from CAD, game engines, or design tools and need to get them into a USD pipeline, Autoconverter converts STL, OBJ, FBX, SKP, STEP, GLTF, DAE, IFC, and 30+ other formats directly to USD, USDA, USDC, and USDZ on Windows.
USD vs USDA vs USDC vs USDZ: Which Variant to Use
USD comes in four file variants. Choosing the right one matters for your pipeline:
| Extension | Format | Best For |
|---|---|---|
| .usd | Can be either ASCII or binary - determined by the writing tool | Generic USD exchange; tool auto-selects encoding |
| .usda | ASCII text - human-readable USD | Development, debugging, manual editing, version control diffs |
| .usdc | Binary Crate format - Pixar's optimized binary encoding | Production pipelines, large scenes, faster loading than USDA |
| .usdz | ZIP package containing USD stage + textures + assets | Apple AR (ARKit, Reality Composer, Quick Look), web delivery, single-file sharing |
For Apple AR Quick Look and ARKit deployment, always use .usdz - it packages the USD stage and all textures in a single self-contained file that iOS and macOS can open directly. For Houdini, Omniverse, or DCC tool interchange, .usdc is faster to load and the standard production choice. For debugging and manual editing, .usda lets you inspect the scene graph structure directly.
What USD Carries vs Other Formats
USD is a scene description format, not just a mesh format - it stores more structure than FBX, OBJ, or GLTF in most cases:
- Scene hierarchy - prim (primitive) tree with parent-child relationships; assembly structure is preserved
- Polygon mesh geometry - vertex positions, face topology, normals, UV sets
- Subdivision meshes - Catmull-Clark and Loop subdivision surfaces with crease data (see the USD subdivision mesh guide)
- PBR materials - UsdPreviewSurface materials with diffuse, roughness, metallic, normal map, and emissive channels
- Textures - referenced externally in USD/USDA/USDC; embedded in USDZ
- Instance references - USD point instancers and scenegraph instancing for repeated geometry (compact representation of arrays of identical objects)
- Variants - USD variant sets allow a single asset to contain multiple configurations (e.g., different color options) selectable at load time
When converting from simpler formats (STL, OBJ, STEP) to USD, only the data present in the source format transfers. STL to USD produces a USD mesh prim with geometry only. FBX to USD produces geometry, materials, and hierarchy. SKP to USD preserves component instances as USD scenegraph instances.
Common 3D to USD Conversion Paths
STL to USD / USDZ
STL contains only triangulated geometry - no materials, no hierarchy, no names. Converting STL to USD or USDZ produces a single mesh prim. For Apple AR, apply a USD material in a USD-aware tool (Reality Composer, Blender with USD plugin) after conversion for realistic rendering. USDZ is the correct target for ARKit Quick Look.
OBJ to USD / USDZ
OBJ carries geometry, UV maps, and materials via the MTL file. Converting to USD preserves the geometry and creates UsdPreviewSurface materials from the MTL data. Texture images referenced by the MTL are embedded in USDZ output or placed alongside the USD file for USDA/USDC output.
FBX to USD
FBX is one of the richer source formats for USD conversion - it carries scene hierarchy, materials, UV maps, textures, and animation. Converting FBX to USDC produces a structured USD stage with the same object tree, materials mapped to UsdPreviewSurface, and animation data where present.
SKP to USDZ (SketchUp to Apple AR)
SketchUp architectural and product models convert to USDZ for deployment in Apple AR Quick Look - allowing clients to place models in real spaces on iPhone or iPad. SKP component instances are preserved as USD scenegraph instances in the output, keeping the USDZ file compact for AR delivery.
STEP to USD
STEP NURBS solids are tessellated to polygon mesh during conversion. The resulting USD contains mesh prims. For engineering visualization in Omniverse or other USD-based review tools, this provides a lightweight mesh representation of precision CAD geometry.
GLTF / GLB to USD
GLTF and GLB carry PBR materials that map cleanly to UsdPreviewSurface. Converting GLTF to USDC or USDZ is useful for bringing web 3D assets or game assets into Houdini or Omniverse USD pipelines.
How to Convert to USD Using Autoconverter
- Download and install Autoconverter on Windows and launch it.
- Go to File > Open and load your source file (STL, OBJ, FBX, SKP, STEP, GLTF, or any supported format).
- Go to File > Save As and choose the target USD variant from the format dropdown: USD (*.usd), USD ASCII (*.usda), USD Binary (*.usdc), or USD ZIP (*.usdz).
- Click Save. For USDZ, textures from the source model are automatically embedded in the package.
For batch conversion of multiple files to USD, use File > Batch Convert, select the source folder and target USD variant, and click Start.
Frequently Asked Questions
What is the difference between .usd and .usdc?
A .usd file can be either ASCII or binary - its actual encoding is determined by which tool wrote it. .usdc always means the binary Crate format. For production pipelines where you need guaranteed binary encoding for fast loading, save as .usdc explicitly rather than .usd.
Which USD variant should I use for Apple AR / ARKit?
USDZ (.usdz). Apple's ARKit, Reality Composer, and iOS Quick Look require USDZ - a ZIP package containing the USD stage and all texture assets. USDA or USDC with external textures will not open correctly in Apple's AR tools.
Does converting FBX to USD preserve animations?
No. Autoconverter does not read, process, or export animation data contained in the source FBX file. The software focuses on converting 3D geometry, materials, textures, and other model data, but animated objects, skeletal rigs, keyframes, morph targets, and animation timelines are not preserved during conversion.
Is there a free trial?
Yes. The free evaluation version of Autoconverter supports up to 10 file conversions including USD, USDA, USDC, and USDZ export. The full licensed version provides unlimited conversions and batch processing.
Summary
Autoconverter converts STL, OBJ, FBX, SKP, STEP, GLTF, DAE, IFC, and 30+ other formats to all four USD variants - .usd, .usda, .usdc, and .usdz. Use USDZ for Apple AR and single-file sharing; USDC for production pipeline interchange; USDA for development and debugging. Textures embed automatically in USDZ output. STEP and IGES NURBS solids tessellate to polygon mesh prims during conversion.
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