Importing Models

How to Open a File

There are several ways to import a 3D model into Gantry:

1. File menu: Choose File → Open (⌘O) and select your model
2. Toolbar: Click the Import button in the toolbar
3. Drag and drop: Drag a file from Finder into the Gantry window
4. Dock: Drag a file onto the Gantry icon in the Dock to open it, even if Gantry isn’t running

To work with multiple models at the same time, use File → New Window (⌘N) to open additional windows.

Opening Files on iOS and iPadOS

On iPhone and iPad, Gantry uses the system file picker. You can select either a single model file or a folder that contains model files.

When you select a folder, Gantry scans it for supported 3D models:

• If the folder contains one supported model, Gantry opens it directly.
• If the folder contains several supported models, Gantry shows a system list so you can choose which model to open.
• If the folder contains no supported models, Gantry asks you to pick a different file or folder.

Some formats reference files beside the main model. For example, a .gltf file may reference external .bin buffers for geometry and image files for textures, and an .obj file may reference a .mtl material file. iOS and iPadOS only grant Gantry access to the exact file or folder you choose, so Gantry may ask you to select the containing folder before it can load those companion files.

Gantry separates required companion files from optional ones:

• Required files are needed to open the model correctly. For glTF, external .bin buffers are required because they contain geometry data. If they are missing or inaccessible, Gantry asks for the folder that contains them.
• Optional files improve the result but are not always required to open the model. Texture images are usually optional. You can choose Open Without Textures to load the model without them.

If you choose a folder that contains only some of the companion files, Gantry uses the files it can access. It will continue only if all required files are available; otherwise it keeps asking for a folder that contains the missing required payloads.

Supported Import Formats

Universal Scene Description

• .usd — USD (auto-detects ASCII or binary encoding)
• .usda — USD ASCII (human-readable text)
• .usdc — USD Crate (compact binary)
• .usdz — USDZ archive (self-contained, used for AR and Apple platforms)

3D Interchange Formats

• .fbx — Filmbox, widely used for character and animation exchange
• .gltf / .glb — glTF, the Khronos Group open standard for runtime 3D
• .obj — Wavefront OBJ, a simple mesh format with optional .mtl materials
• .abc — Alembic, used for baked geometry and point caches

Specialized Formats

• .ply — Polygon File Format, common for scanned point clouds and meshes
• .stl — Stereolithography, commonly used in 3D printing workflows
• .sbsar — Adobe Substance material archive
• .spz — Gaussian Splat scene format

Format Conversion Notes

When importing non-USD formats, Gantry converts the file into USD for viewing and editing. Some format-specific features may not translate directly:

• Vertex colors are written to the displayColor attribute but are not used by the RealityKit renderer
• Opacity masks support only fully opaque (1.0) or fully transparent (0.0) values — intermediate alpha is not supported
• Double-sided geometry is not natively supported; faces must be duplicated to achieve this effect

After Importing

Once a model is loaded you’ll see:

• The model name in the window title
• A live 3D preview in the RealityKit viewport
• Material editing controls in the inspector panel
• Stage metadata (up-axis, scale, default prim) in the inspector’s Stage Properties section
• Animation and blend shape controls if the model contains them

Select Objects in the Viewport

Click any object in the viewport to select it. The inspector will update to show that object’s materials.