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Untold Engine

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Untold Engine is a Swift + Metal 3D engine for macOS, iOS, and visionOS — with native Apple Vision Pro support and a growing focus on spatial computing — built for developers who:

  • Want full control over rendering and systems
  • Prefer working directly with Swift + Metal
  • Are building XR, 3D, or visualization applications
  • Need to handle large scenes, streaming data, or custom pipelines

If you've hit the ceiling of what existing engines allow on Apple platforms, this is for you.

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Creator & Lead Developer:
Harold Serrano

Watch It in Action — Apple Vision Pro Demos

Try the Engine Right Now

The fastest way to experience Untold Engine is to run the demo project.

Clone the repository and launch the demo:

git clone https://github.com/untoldengine/UntoldEngine.git
cd UntoldEngine
swift run untolddemo

The demo UI lets you see the engine in action right away. Using the Remote Scene drop-down menu, you can choose a scene to stream directly into the demo through the engine's Asset Remote Streaming support.

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I want to try my own USDZ

Untold Engine uses its own native asset format: .untold.

To try your own USDZ file, first convert it to .untold using the Tools section in the demo UI.

After the export is complete, open the Local Scene Browse drop-down menu, choose .untold, then browse for and select your exported .untold file.

Note: The exporter requires Blender.

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Getting Started

To create your own project using the Untold Engine, see Getting Started.

Core Direction

Untold Engine is built around three focused goals:

  • Spatial Engine First — Designed for spatial computing applications. LOD, geometry streaming, and static batching exist to support large, real-world-scale environments where presence and performance both matter.

  • XR / visionOS Support — Spatial input, AR workflows, and Vision Pro support are functional today and expanding with each release.

  • Metal-First Architecture — The rendering layer stays close to Metal to maintain performance and control, without abstraction layers getting in the way.

Example Use Cases

Untold Engine is well-suited for:

  • XR applications (Vision Pro, ARKit-based apps)
  • Large-scale scene visualization (cities, archviz, datasets)
  • Custom rendering pipelines and experiments
  • Simulation tools and interactive 3D systems

Current Features

  • Apple Platform Coverage — Unified Swift + Metal codebase for macOS, iOS, and visionOS
  • Rendering Pipeline — Metal renderer with PBR/IBL workflows and post-processing across standard and XR paths
  • AR and XR Runtime Support — Built-in AR workflows plus visionOS integration and spatial interaction support
  • ECS + Scene Graph Core — Component-based architecture with hierarchical transforms and scene root transform controls
  • Async Content Loading — Asynchronous loading pipeline for scenes and assets to improve responsiveness on large worlds
  • LOD and Streaming — LOD support with geometry streaming, streaming regions, and memory budget management
  • Static Batching and Culling — Static batching, octree acceleration, and occlusion culling for large-scene performance
  • Advanced Picking — Scene, ground, and GPU ray picking with octree-backed intersection paths
  • Spatial Input Features — XR spatial input helpers including anchored pinch drag, distance tracking, and two-hand rotation
  • Scripting System (USC) — Untold Script Core with multi-script support plus camera, math, and physics APIs (Experimental)
  • Gameplay Systems — Physics, animation, camera waypoint, and input systems (keyboard, mouse, touch, and gamepad)
  • Gaussian Splat Rendering — Native Metal support for rendering and compositing 3D Gaussian content
  • Tooling Integration — Optional Untold Editor workflow and Swift Package Manager integration

Roadmap

See open issues for planned features and known improvements.

Contributing

Contributions are welcome — whether that's fixing bugs, improving systems, writing documentation, or proposing ideas.

Before submitting a pull request, please review the Contributing Guidelines.

All contributions are licensed under MPL-2.0.

GitHub Sponsors

A huge thanks to the people helping shape the Untold Engine.

MioLabs

License

Untold Engine is licensed under the Mozilla Public License 2.0 (MPL-2.0).

This allows developers to build commercial applications while ensuring improvements to the engine itself remain open.

Use Case Allowed Obligation
Build games Yes Game code can remain proprietary
Commercial apps Yes No royalties
Modify engine Yes Modified engine files remain MPL
Create plugins Yes Any license allowed

Full license: https://www.mozilla.org/MPL/2.0/

Questions & Discussions