uLoader Node

uLoader reads a USD file and exposes the 3D scene it contains (meshes, materials, lights, cameras, animation) in Fusion. Its output connects to a uMerge or directly to a uRenderer for rendering.

Unlike the classic Loader, which reads images, the uLoader reads 3D content. It is the hub of the modern 3D workflow in compositing.

• Effects Library: Tools > USD > uLoader
• Quick add: right-click in the Node Editor → Add Tool > USD > uLoader

Universal Scene Description

An open format created by Pixar to describe complete 3D scenes. It has become an industry standard (Houdini, Maya, Blender, Unreal, Omniverse, etc.).

Layered / Composable

USD lets you have several layers that compose together: a USD asset + its separate USD animation + its separate USD shading = a modular scene.

Time-aware

USD natively supports animation: positions, mesh deformations and properties over time are stored in the file.

Variants

An asset can have several variants (LOD, versions, costumes) selectable at load time.

• No visual inputs; it is configured through parameters.
• Output (green) - the loaded USD scene, connectable to the other USD nodes.

Basic USD workflow:
uLoader (asset.usd) → uRenderer → MediaOut

Multi-asset:
uLoader (character.usd) ─┐
                          ├── uMerge ── uRenderer ── MediaOut
uLoader (set.usd) ───────┘

USD with layers:
uLoader (base.usd, Layer = animation_layer.usd)
   = base + animation layer composed at load time

USDZ archive:
uLoader (asset.usdz) = a self-contained archive (assets + textures included)
   = handy for sharing without dependencies

Filename (default: empty)

Path of the USD file to load. Use the browser on the right to pick it.

Sublayers

A list of additional layers to compose on top of the main file.

Variant Selection

If the USD contains variants, choose which one to load (e.g. LOD0, LOD1, costume A, costume B).

Time Offset (default: 0)

Offset of the USD animation relative to the Fusion timeline. Lets you shift the animation without modifying the USD.

Frame Rate (default: 24)

Frame rate of the animation. It must match the project for correct sync.

Stage Up Axis (default: Y)

Vertical axis of the coordinate system. Houdini/Maya = Y, Blender = Z. Adapt it to the source.

• Importing Houdini / Maya / Blender assets - assets exported as USD from any DCC = read directly in Fusion.
• Modern VFX pipeline - USD is the industry standard. Pro studios build their pipeline around USD.
• Omniverse / Unreal workflow - assets exported as USD from these engines load into Fusion for compositing.
• Standardized asset library - a library of USD assets shared between artists / projects.
• Complex modular scene - load a layered USD scene: base + animation + shading = flexible compositing.
• USDZ for clients / review - a self-contained USDZ archive you can send to the client, which opens in Fusion or another viewer.

• USD requires Resolve Studio - full USD support is in the Studio version. The free version has limited support or none at all.
• Correct Up Axis - Y vs Z depending on the source. A mismatch = a scene tipped over. Check when loading and adapt.
• USDZ = self-contained archive - prefer it for sharing: everything in one file (textures, mesh, etc.). Avoids broken paths.
• Performance - a heavy USD can slow things down. For massive scenes, consider Levels of Detail (LOD) through variants.
• Layers for a studio pipeline - in a pro pipeline, base (rig) + animation (per shot) + shading (per look) in separate layers = a non-destructive workflow.
• Time Offset for reuse - the same USD asset used at different moments: each uLoader with its own Time Offset.
• Check version compatibility - USD evolves (1.0, 1.1, 1.2...). Fusion supports a range of versions; a USD that is too recent may not load.
• For pro studio workflows, USD integrates with Shotgun, ftrack and Perforce for collaborative versioning.