**Stack 4/5** — base #4125. Part of the #4096 split; see #4096 for the
overall picture.
> Review after #4123, #4124 and #4125.
## What this is
The generic OPC UA to OpenUSD binding, scene materialization, and the
connector that drives a live stage from a running server.
## Contents
**Binding (Part 1)** — `Opc.Ua.OpenUsd` and `Opc.Ua.OpenUsd.Server`. A
server describes how its Variables drive USD prims, and serves the USD
layers it refers to as Part 5 files with a content digest.
**Scene materialization (Part 2)** — `Opc.Ua.OpenUsdScene` and
`Opc.Ua.OpenUsdScene.Server`, including the USDA writer.
- **Escaping fix**: string values, composition-arc references, variant
set names and selections, `doc` and prim names were all emitted
unescaped, so a value carrying a quote or a newline could author its own
layer syntax. Every emit site now goes through the escapers. The tests
assert the right property — not that the payload is absent (it
legitimately survives inside the escaped literal) but that no payload
becomes its own line of layer syntax.
**Client** — `Opc.Ua.OpenUsd.Client` streams live values into an
`IUsdSink`. `CompositeUsdSink` fans out to several sinks; the file sink
interpolates between server samples so motion is continuous rather than
stepped at the publishing interval.
**Connector** — `tools/Opc.Ua.OpenUsd.Connector` composes a stage from a
live server. The optional in-process viewport lives in a separate
assembly probed at run time, so the connector still runs — and says why
— when it is absent.
- **Fix**: the asset cache and PKI root moved off the shared temp
directory to `LocalApplicationData`.
**Sample** — `PumpDeviceIntegrationServer` gains an OpenUSD
representation of the pump.
## Notes for the reviewer
- The viewport assembly is net10.0-only. It is what exercises the
`Directory.Build.targets` change from 1/5: without it, the `net8.0` leg
of the per-TFM CI build fails with `CS0433` because the
`System.Threading.Lock` polyfill collides with the real type.
- `UsdAssetDelivery` hashes through `SHA256.Create` rather than the
static `HashData`, which does not exist on the net472/net48 targets this
test project also builds for.
## Validation
`dotnet build UA.slnx` — 0 errors, 0 warnings.
| Suite | Result |
| --- | --- |
| Opc.Ua.OpenUsd.Tests | 621 / 0 |
| Opc.Ua.Di.Tests | 321 / 0 |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8cbb8cd0-f0cb-4ab0-bea2-6202fbf69485
Marc Schier