I’m trying to get clarity on the current state of runtime USD support in UE 5.5–5.6, specifically when using UsdStageActor to load USD files directly at runtime (no import, no baking, no uassets).
We’ve built Unreal from source, enabled the documented USD runtime flags, and confirmed:
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UsdStageActor loads correctly
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SetRootLayer() succeeds at runtime
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USD modules compile in Runtime, not just Editor
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Editor-only plugins are disabled
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USD libs/DLLs are packaged correctly
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No content is imported into the Content Browser
Despite this, UE 5.5–5.6 consistently prioritizes asset import & cached meshes over the live USD stage. Even when:
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Loading a USD file at runtime
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Cached assets are removed
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Auto-import is disabled
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Editor-only code paths are stripped
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The USD loads cleanly in the USD Stage panel
Unreal tends to resolve geometry/materials from the cached import pipeline instead of the USD being loaded at runtime. This makes USD behave inconsistently or unpredictably — essentially blocking USD from functioning as a live scene graph.
Context: This used to work reliably
Back in UE 5.1–5.2, using the Omniverse Live Link workflow, this exact behavior did work:
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USD stages streamed into Unreal
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Geometry updated live without baking
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Materials (even basic Preview Surface) propagated
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No import/cache pipeline interference
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UsdStageActor behaved like a true live USD host
That earlier workflow showcased what many of us expect from USD:
live updates, no baking, no asset import pipeline in the way.
It seems the newer engine versions shift more toward import/caching pipelines and away from runtime USD as a first-class path.
My questions:
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Is this change intentional in UE 5.5/5.6?
Is Unreal moving away from supporting live USD workflows in favor of import/cache-driven pipelines? -
Is there still a fully supported path for using USD as a live stage at runtime (via UsdStageActor), without auto-import or cached assets taking priority?
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Are there additional flags, build settings, or plugin modifications needed to re-enable fully functional runtime USD behavior?
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If Live USD was supported in 5.1–5.2 (including via Omniverse Live Link), is there a recommended migration or replacement strategy for developers relying on runtime USD integration?
We’re trying to understand Unreal’s intended direction so we can align our pipeline correctly.
Any guidance from Epic or developers working heavily with USD would be hugely appreciated.