Editing Materials

Gantry lets you edit material properties directly in the inspector. Changes are applied in real-time to the RealityKit viewport preview and written as a new undo layer so they can be reversed with ⌘Z.

Property Types

Colors

Color properties (such as Diffuse Color or Emissive Color) open the macOS color picker. You can choose from the color wheel, enter exact RGB or hex values, or use the eyedropper to sample from anywhere on screen.

Values

Numeric properties (such as Metallic or Roughness) are adjusted with a slider or by clicking to enter a precise number. Values are clamped to their valid range (typically 0.0–1.0).

Textures

Texture-mapped properties show a thumbnail preview of the assigned image. You can drag a new texture file onto the thumbnail to replace it, or clear it to fall back to a solid color or value. Supported texture formats: PNG, JPEG, HEIC, TIFF, AVIF, BMP.

USD Preview Surface Inputs

USD Preview Surface is the standard USD material model and is the format Gantry edits most directly. The following inputs are supported:

Input	Type	Description
diffuseColor	Color / Texture	Base color of the surface (albedo)
emissiveColor	Color / Texture	Self-illumination color; adds light without a light source
metallic	Value / Texture	0 = dielectric (plastic), 1 = conductor (metal)
roughness	Value / Texture	0 = mirror-smooth, 1 = fully diffuse
clearcoat	Value / Texture	Intensity of a secondary specular layer (car paint, lacquer)
clearcoatRoughness	Value / Texture	Roughness of the clearcoat layer
opacity	Value / Texture	Surface transparency; 1 = fully opaque
normal	Texture	Tangent-space normal map for surface detail
occlusion	Texture	Ambient occlusion map; darkens crevices and contact shadows

Note: the specular workflow (specularColor / useSpecularWorkflow) is not currently supported by Apple’s RealityKit renderer. Use the metallic/roughness workflow instead.

Note: only a single UV map per material is supported. Multiple UV sets are not used.

Material Formats

Gantry supports four material formats. The inspector shows which format each material uses:

• USD Preview Surface — The standard USD PBR material. Full editing support. Best compatibility across USD tools and Apple platforms.
• MaterialX — An industry-standard material network format. Full editing support for standard PBR surface inputs.
• RealityKit — Apple’s native material format, optimised for the RealityKit renderer. Full editing support.
• OpenPBR — An emerging open standard for physically-based rendering. View support; editing of some parameters may be limited.

Edit Policy

The “When editing” dropdown in the inspector controls how Gantry applies changes to a material’s format:

• Preserve Authored Mode — Keeps the existing material format. Only the values you change are modified. This is the default and safest option.
• Canonicalize to PreviewSurface — Converts the material to USD Preview Surface before applying edits. Use this to standardise materials from mixed-format files.
• Convert to MaterialX PreviewSurface — Converts and edits within the MaterialX format.

Undo Edits

Press ⌘Z to undo the last material edit. Each change is written as a separate layer, so you can step back through individual edits.

Format Conversion Changes Appearance

Converting between material formats may alter the appearance of a material, because different formats support different features. Always review the result in the viewport before exporting.