OpenUsd

A high-performance, NativeAOT-compatible .NET data and rendering stack for OpenUSD, plus an Avalonia desktop viewer.

OpenUsd keeps OpenUSD C++ types behind a versioned, project-owned C ABI. Its managed surface covers stages, layers, prims, typed values, composition, focused schema facades, ordered live authoring, and renderer-neutral state. Hydra/Storm is the primary renderer; Hydra-fed Silk.NET backends provide D3D12, Vulkan, and Metal alternatives without putting per-element P/Invoke on scene or render hot paths.

Current distribution: public source repository, version 0.1.0-alpha, and pre-1.0 APIs. Packages are built and exercised through local feeds and CI, but this project does not currently advertise a public NuGet or GitHub Packages installation path.

✨ Highlights

• Idiomatic data API for stage and layer lifecycle, prims, attributes, relationships, variants, metadata, composition arcs, world bounds, and bulk values.
• Focused schemas for UsdGeom, UsdShade, UsdLux, and UsdSkel.
• Owned native boundary with opaque handles, bulk buffers, explicit lifetime rules, and no exposure of OpenUSD C++ layouts.
• Ordered shared-stage access through UsdStageScheduler, change notifications, and retained render sources for live editing.
• Renderer-neutral viewer state for camera, time, selection, picking, diagnostics, and failover.
• Cross-platform packaging gates for win-x64, linux-x64, and osx-arm64.
• NativeAOT and trimming analyzers across production libraries targeting .NET 8, 9, and 10.

🚀 Start from source

The repository pins .NET SDK 10.0.301. The managed baseline does not build OpenUSD itself:

git clone https://github.com/marcschier/openusd-dotnet.git
cd openusd-dotnet
dotnet --version
dotnet build OpenUsd.slnx -c Release
./eng/run-managed-tests.ps1 -Configuration Release
dotnet build samples/OpenUsd.HelloStage/OpenUsd.HelloStage.csproj -c Release -f net10.0

dotnet --version must print 10.0.301. If it is unavailable, use ./eng/install-dotnet.ps1 on Windows or bash ./eng/install-dotnet.sh on macOS/Linux. Managed projects compile without OpenUSD; executing OpenUsd.HelloStage requires the matching Core runtime.

For the native-backed API, inspect and build the locked runtime for the current RID:

./eng/build-native.ps1 -Rid win-x64 -PlanOnly
./eng/fetch-native.ps1 -Rid win-x64
./eng/build-native.ps1 -Rid win-x64
./eng/run-native-probe.ps1 -Rid win-x64

The public API used by the native probe and package consumers starts like this:

using OpenUsd;

using UsdStage stage = UsdStage.Create("scene.usda");
UsdPrim world = stage.DefinePrim("/World", "Xform");
world.SetString("custom:greeting", "hello");
stage.SetDefaultPrim("/World");
stage.Save();

See Getting started for platform prerequisites, native staging, the viewer, and NativeAOT commands. The runnable source setup is in the HelloStage guide, and the complete API walkthrough is in Data API.

🏗️ Architecture

flowchart LR
    App[Application or sample] --> Data[OpenUsd data API]
    Viewer[Avalonia Viewer] --> Data
    Viewer --> Neutral[OpenUsd.Rendering]
    Data --> Interop[OpenUsd.Interop]
    Interop --> CABI[Project-owned C ABI]
    CABI --> USD[OpenUSD C++]
    Neutral --> Storm[Hydra / Storm]
    Neutral --> Silk[Hydra / hdSilk pages]
    Storm --> Interop
    Silk --> Interop
    Silk --> RHI[D3D12 / Vulkan / Metal]

Loading

The data facade, renderer-neutral contracts, Hydra translation, and concrete RHIs remain separate. Large scene and render payloads cross owned bulk boundaries rather than one native call per element. See Architecture and Rendering.

📦 Package matrix

All package IDs below are buildable from this repository. They are not currently published to a public package feed.

Package	TFM	Purpose
OpenUsd.Interop	8/9/10	Generated NativeAOT-safe C ABI declarations
OpenUsd	8/9/10	Managed stage, layer, prim, value, and schema API
OpenUsd.Rendering	8/9/10	Renderer-neutral state, capabilities, picking, and failover
OpenUsd.Rendering.Storm	8/9/10	Hydra/Storm adapter
OpenUsd.Rendering.Silk	8/9/10	Hydra-fed managed renderer and backend-neutral RHI
OpenUsd.Rendering.Silk.D3D12	8/9/10	Direct3D 12 backend
OpenUsd.Rendering.Silk.Vulkan	8/9/10	Vulkan backend
OpenUsd.Rendering.Silk.Metal	8/9/10	Metal backend
OpenUsd.Runtime.Core.win-x64	8 carrier	Windows OpenUSD core runtime and data plugins
OpenUsd.Runtime.Core.linux-x64	8 carrier	Linux OpenUSD core runtime and data plugins
OpenUsd.Runtime.Core.osx-arm64	8 carrier	macOS OpenUSD core runtime and data plugins
OpenUsd.Runtime.Imaging.win-x64	8 carrier	Windows Hydra, Storm, hdSilk, and plugins
OpenUsd.Runtime.Imaging.linux-x64	8 carrier	Linux Hydra, Storm, hdSilk, and plugins
OpenUsd.Runtime.Imaging.osx-arm64	8 carrier	macOS Hydra, Storm, hdSilk, and plugins

Runtime projects use net8.0 as their NuGet asset-carrier TFM; the managed libraries they accompany target .NET 8, 9, and 10. Package layout and clean-consumer gates are documented in Packaging.

🎯 Target frameworks

Surface	net8.0	net9.0	net10.0	Notes
Packable managed libraries	✅	✅	✅	AOT, trim, and single-file analyzers enabled
OpenUsd.LiveAuthoring sample library	✅	✅	✅	Source sample, not a package
Runtime asset carrier projects	Carrier	—	—	RID assets consumed by supported applications
Viewer, executable samples, probes	—	—	✅	Repository development and evidence tools

🖥️ RID and viewer matrix

The package prefix in the runtime columns is OpenUsd.Runtime..

RID	Core package	Imaging package	Viewer choices	Evidence
win-x64	Core.win-x64	Imaging.win-x64	Storm, D3D12, Vulkan	Native, package, render gates
linux-x64	Core.linux-x64	Imaging.linux-x64	Storm, Vulkan	Native, package, render gates
osx-arm64	Core.osx-arm64	Imaging.osx-arm64	Storm, Metal	Hosted end-to-end proof still pending

See Support matrix for the distinction between implemented source, workflow-defined gates, and hosted execution evidence.

🎨 Renderer and backend matrix

Viewer kind	Scene source	Presentation/API	RID	Role
Storm	Hydra/Storm	WGL, GLX, or NSOpenGL host	all supported	Primary
D3D12	Hydra to hdSilk pages	Direct3D 12	win-x64	Managed fallback
Vulkan	Hydra to hdSilk pages	Vulkan	win-x64, linux-x64	Managed fallback
Metal	Hydra to hdSilk pages	Metal	osx-arm64	Managed fallback

The renderer-neutral capability declarations are:

Capability	Storm	D3D12	Vulkan	Metal
Presentation	✅	✅	✅	✅
Offscreen	—	✅	✅	✅
Compute	—	✅	✅	✅
Multisampling	Up to 8x	1x	1x	1x
Shadows	✅	—	—	—
Device-loss detection	✅	✅	✅	✅
One-pixel picking	✅	✅	✅	✅
Selection display	Storm highlight	Visible outline	Visible outline	Visible outline

An em dash means the capability is not advertised by the current renderer-neutral descriptor, not that the underlying graphics API can never provide it.

🧩 Feature matrix

Area	Current alpha coverage	Status
Stage and layer lifecycle	Create, open, masked open, save, reload, export, edit targets, muting	Implemented
Prim lifecycle	Define, override, class prims, traversal, children, active/load/instance state	Implemented
Values	Scalars, arrays, matrices, vectors, quaternions, colors, tokens, time samples	Implemented
Relationships	Create, enumerate, replace, read, and clear targets	Implemented
Composition	References, payloads, inherits, specializes, sublayers, population masks	Implemented
Variants and metadata	Variant sets/selections plus typed prim and layer metadata	Implemented
UsdGeom	Xform, xformable, imageable, mesh, camera, bounds, transforms	Focused facade
UsdShade	Materials, shaders, preview surface, UV texture, connections, binding	Focused facade
UsdLux	Distant, sphere, rect, disk, dome, cylinder, common light/shaping API	Focused facade
UsdSkel	Root, skeleton, animation, binding, joints, transforms, influences	Focused facade
Shared-stage authoring	Scheduler, change feed, retained render source, bounded sample queue	Implemented
Viewer	Hierarchy, properties, layers, timeline, cameras, switching, diagnostics	Implemented
Primitive picking	Storm and hdSilk backend paths with stale-result handling	Implemented
Face picking	hdSilk preserves authored triangle/subprim identity	Implemented on Silk
Edge and point picking	Valid requests report unsupported	Not supported
Selection outlines	Visible-only hdSilk outline; Storm uses its native highlight	Implemented
X-ray selection	Explicitly rejected by the current outline contract	Not supported
NativeAOT	Compile gates on all RIDs; package-only execution gates per RID	Alpha-gated

🗺️ Repository map

Path	Contents
src/	Managed data, interop, rendering packages, runtime packages, and Viewer
native/	Project C ABI shims, Hydra integration, CMake inputs, and native tests
samples/	Managed smoke and ordered live-authoring examples
tests/	Managed, native, package, rendering, performance, and Viewer evidence
benchmarks/	BenchmarkDotNet workloads
eng/	SDK, native, shader, packaging, test, performance, and Viewer scripts
test-assets/	Repository-owned USD fixtures and fuzz seeds
docs/	Architecture, API, rendering, packaging, testing, and contributor guides

🧪 Samples

Sample	Purpose	Native runtime
OpenUsd.HelloStage	Create/save/open round trip	Required to run
OpenUsd.LiveAuthoring	Ordered update adapter	No for build/tests
OpenUsd.LiveAuthoring.Sample	End-to-end authoring	Required

See the samples overview for prerequisites, expected output, and package versus source consumption.

📚 Documentation

Start here	Use it for
Documentation hub	Audience-oriented routes through all project docs
Getting started	Source build, native staging, Viewer, and AOT
Support matrix	Framework, RID, renderer, backend, and feature status
Architecture	Layering, ownership, and bulk native boundaries
Programming model	Ownership, scheduling, cancellation, errors, paths, and AOT
Data API	Public stage, prim, value, composition, and schema APIs
Live authoring	Ordered batches, backpressure, consumers, and disposal
Rendering	Renderer-neutral contracts, Storm, hdSilk, picking, and selection
Viewer	Desktop workflows, camera controls, editing, and diagnostics
Samples	Runnable data API and live-authoring examples
Native build	Locked OpenUSD inputs, toolchains, and native probes
Packaging	Runtime asset layout and clean package consumers
Versioning	Managed, ABI, package, runtime, and plugin compatibility
Shader pipeline	Reproducible DXIL, SPIR-V, and Metal inputs
Performance	Boundary shape, allocation gates, resources, and benchmarks
Testing	Managed runner, conformance, performance, and platform evidence
Troubleshooting	Native loading, plugins, platforms, AOT, and evidence triage

🛠️ Build, test, and NativeAOT

dotnet restore OpenUsd.slnx
dotnet build OpenUsd.slnx -c Release --no-restore
./eng/run-managed-tests.ps1 -Configuration Release
dotnet format OpenUsd.slnx --verify-no-changes --no-restore
./eng/check-line-length.ps1
./eng/test-documentation.ps1
./eng/run-performance.ps1

Managed tests use TUnit on Microsoft.Testing.Platform. Use eng/run-managed-tests.ps1, not a bare dotnet test, for the repository's verified execution path. Targeted commands are in Testing.

The same NativeAOT compile smoke used by CI can be reproduced with the platform AOT toolchain. On Windows, run it from an x64 Visual Studio developer shell:

dotnet publish samples/OpenUsd.HelloStage/OpenUsd.HelloStage.csproj -c Release -f net10.0 -r win-x64 -p:PublishAot=true

Native-backed execution additionally requires the matching locked runtime and shim. Use eng/run-native-probe.ps1 after the native build rather than manually assembling loader paths.

🚧 Non-goals

• A stable public package or API compatibility promise before 1.0.
• Direct bindings to the OpenUSD C++ ABI or exposure of C++ object layouts.
• Per-prim, per-vertex, or per-element P/Invoke on scene and render hot paths.
• Complete generated coverage of every OpenUSD schema and optional component.
• A replacement for usdview, a full DCC, or a general-purpose game engine.
• Runtime packages for RIDs outside win-x64, linux-x64, and osx-arm64 today.
• Bundling Python, usdview, tutorials, examples, Embree, Alembic, Draco, OpenVDB, or RenderMan in the locked native profile.

🔒 Security

Treat USD files, asset paths, plugin metadata, and native package contents as untrusted input. Report vulnerabilities privately through GitHub Security Advisories; do not open a public issue. See Security.

🤝 Contributing

Keep changes focused, analyzer-clean, deterministic, and separated across data, renderer-neutral, Hydra translation, and concrete backend layers. Native or public API changes require corresponding tests and documentation. See Contributing.

📄 License

MIT. OpenUSD and bundled third-party native dependencies retain their own licenses; see NOTICE.

Status

OpenUsd is a substantial public 0.1.0-alpha source baseline, not a stable release. Data, rendering, Viewer, package, NativeAOT, shader, and performance gates exist, but public API and package identities may change before 1.0. Workflow badges above are the authoritative status for the default branch.