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Preflight Documentation

USD Platform Support

One of the most persistent misconceptions in USD development is that OpenUSD and its Hydra rendering engine are too complex or heavyweight to run on mobile and spatial platforms like iOS and visionOS.

Preflight is built on the fact that this is no longer true. The apple/SwiftUsd distribution provides first-class support for these platforms, enabling the “Dual Viewport” experience that defines the Preflight workflow across the entire Apple ecosystem.

Support Matrix

Section titled “Support Matrix”
FeaturemacOSiOS 17+visionOS 1+
OpenUSD Core (Sdf, Usd, Pcp)✅✅✅
Hydra Framework (Hd)✅✅✅
Storm Renderer (HdSt)✅✅✅
Metal Backend (HgiMetal)✅✅✅
glTF / OBJ / STL Plugins✅✅*✅*
FBX Plugin✅✅*✅*
Embree Raytracer (HdEmbree)✅❌❌
Python Bindings✅❌❌

* Requires recompilation for the target platform SDK.

Technical Findings

Section titled “Technical Findings”

1. Hydra on Mobile is Metal-Native

Section titled “1. Hydra on Mobile is Metal-Native”

The standard Pixar OpenUSD distribution relies heavily on OpenGL. However, Apple’s SwiftUsd distribution includes HgiMetal (Hydra Graphics Interface for Metal). This allows the Hydra rendering pipeline to drive Apple’s Metal API directly, providing desktop-class rendering performance on iPhone, iPad, and Apple Vision Pro.

2. Compiled for arm64 Silicon

Section titled “2. Compiled for arm64 Silicon”

The apple/SwiftUsd package provides pre-built xcframeworks targeting:

  • macos-arm64_x86_64
  • ios-arm64
  • xros-arm64 (visionOS)

This confirms that the entire USD stack—not just the data model—is compiled and optimized for Apple’s mobile and spatial silicon.

3. Conversion Plugins on visionOS

Section titled “3. Conversion Plugins on visionOS”

Preflight’s conversion pipeline (glTF, FBX, OBJ, STL) is designed with portability in mind:

  • Static Linking: All third-party dependencies are statically baked into the plugins, making them self-contained and “App Store safe.”
  • FBX Support: Contrary to legacy assumptions, a native iOS FBX SDK exists from Autodesk. This allows Preflight to achieve full conversion parity even on mobile devices.
  • On-Device Import: Because these plugins can run natively on visionOS, Preflight supports “Live Conversion”—allowing you to drag a raw .gltf or .fbx into your spatial workspace and see it instantly rendered via Hydra.

Why it Matters

Section titled “Why it Matters”

Because the Hydra engine runs natively on these platforms, Preflight can provide a “Source of Truth” viewport even on mobile devices. This eliminates the discrepancy between what a developer sees on their desktop and what the end-user sees in the app.

On visionOS specifically, this means you can validate and “Preflight” your assets inside the headset, ensuring that textures, animations, and scale are perfect before you ever hit “Publish.”

Credits & Sources

Section titled “Credits & Sources”