OPCFoundation.NetStandard.Opc.Ua.Vision.OpenUsd

OPCFoundation.NetStandard.Opc.Ua.Vision.OpenUsd

Offscreen renderer for the draft OPC UA Vision companion server.

This package renders a USD stage camera's view through the OpenUSD Silk backend (D3D12 hardware, D3D12 WARP software, or Vulkan headless) and returns encoded PNG frames through a small ISceneCameraCaptureProvider abstraction. The Vision server can depend on the abstraction without referencing OpenUSD, and degrades to a non-rendering sensor when this optional package is not present.

What it does

The Opc.Ua.Vision.OpenUsd.OpenUsdSceneCameraCaptureProvider fulfills a capture request by:

1. Opening the USD stage from the supplied path or identifier.
2. Resolving the camera prim (view + off-centre projection built from UsdGeomCamera.GetState(time) and GetTransform(time)) - or rendering the automatic default framing when no prim path is supplied.
3. Creating a fresh OpenUsdSilkSession for the request (the SDK's reuse-with-different-camera path is known to silently render nothing).
4. Capturing an RGBA8 frame with SilkFrameCapture.Capture on a shared ISilkGraphicsDevice picked at construction time.
5. Encoding to PNG with an in-repo, dependency-free encoder.
6. Refusing to hand back an all-zero / no-mesh frame as if it succeeded - returning SceneCameraCaptureStatus.BlankFrame with a reason instead.

Device selection

OpenUsdSceneCameraCaptureProvider tries backends in the order that makes sense for the host:

• Windows: D3D12 hardware -> D3D12 WARP (software rasterizer, no GPU) -> Vulkan.
• Linux / other: Vulkan (which the OpenUSD runtime bundles the SwiftShader software ICD for, so CI without a GPU is still functional).

The provider reports the chosen backend and whether it is a software renderer through Backend, and when no backend is available reports IsAvailable = false with a reason. In that case every CaptureAsync returns SceneCameraCaptureStatus.NoRenderingBackend.

Registration

using Opc.Ua.Vision.OpenUsd;
using Microsoft.Extensions.DependencyInjection;

services.AddOpenUsdSceneCameraCaptureProvider(o =>
{
    o.PluginPath = "/path/to/plugin/usd"; // optional; auto-probes AppContext.BaseDirectory
    o.PreferSoftware = false;
});

or without DI:

using var provider = new OpenUsdSceneCameraCaptureProvider(
    new OpenUsdSceneCaptureOptions(), telemetry: null);
SceneCameraCaptureResult result = await provider.CaptureAsync(
    new SceneCameraCaptureRequest
    {
        StageIdentifier = "/path/to/scene.usda",
        PrimPath = "/World/Cam",
        Width = 640,
        Height = 360,
        TimeCode = 0.0,
        Format = SceneCameraImageFormat.Png,
    },
    cancellationToken);

Native payload

The OpenUSD runtime packages ship RID-specific native assets (win-x64, linux-x64, osx-arm64). Publish the consuming application with an explicit RuntimeIdentifier (e.g. dotnet publish -r linux-x64) so the plugin/usd/ tree and the backend native libraries land alongside the executable. The provider then auto-discovers them from AppContext.BaseDirectory.

When the payload is absent — the normal case on unadorned CI legs — the provider still starts, Backend.IsAvailable reports false and every capture returns SceneCameraCaptureStatus.NoRenderingBackend. This is the degrade path the Vision developer guide describes: the sensor stays visible in the address space, browses still work, and only the pixel bytes are absent, so a client can distinguish "no GPU" from a genuine rendering fault.

Related packages

License

OPC Foundation MIT License 1.00 — http://opcfoundation.org/License/MIT/1.00/