# Across the capture-to-render chain, which time base, unit and naming assumptions must be written down because no format in the chain carries them for the next step?

- id: art_01M5MRM0KEPF7E2HQPQTP17ZPG
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T07, T11, T12, T15 · tags: none
- updated: 2026-10-23T16:13:34.694Z
- url: https://veyrul.com/articles/art_01M5MRM0KEPF7E2HQPQTP17ZPG

Across motion and render handoffs, time, units/axes and names are carried differently by each format (ARKit metres; Live Link Face timecode in recordings; Alembic sample times; the USD Alembic reader assuming Y-up and leaving units unset; UsdRender and EXR names as site conventions), so each step needs a user-authored mapping; this is the producer's synthesis over verified statements.

Across motion and render handoffs, time, units/axes and names are carried differently by each format (ARKit metres; Live Link Face timecode in recordings; Alembic sample times; the USD Alembic reader assuming Y-up and leaving units unset; UsdRender and EXR names as site conventions), so each step needs a user-authored mapping; this is the producer's synthesis over verified statements.

Curator qualifications: Zero-fetch review 2026-10-22; syntheses not executed. C3D 59.94 Hz point-rate statement not verified (source not held).

Limitations: Zero-fetch review 2026-10-22; syntheses not executed.

Evidence status: curator/producer inference or synthesis from the cited sources (code read, not executed, where code is cited); correlated desk review (Claude); not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://www.c3d.org/docs/C3D_User_Guide.pdf",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    },
    {
      "url": "https://developer.apple.com/tutorials/data/documentation/arkit/arfaceanchor.json",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    },
    {
      "url": "https://web.archive.org/web/20231226084301id_/https://docs.unrealengine.com/5.3/en-US/recording-face-animation-on-ios-device-in-unreal-engine/",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/usd/usdSkel/doxygen/schemaOverview.dox",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/docs/user_guides/schemas/usdRender/overview.md",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/usd/plugin/usdAbc/alembicReader.cpp",
      "note": "ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox"
    }
  ]
}
```

Evidence claims:
- [inference] Across motion and render handoffs, time, units/axes and names are carried differently by each format (ARKit metres; Live Link Face timecode in recordings; Alembic sample times; the USD Alembic reader assuming Y-up and leaving units unset; UsdRender and EXR names as site conventions), so each step needs a user-authored mapping; this is the producer's synthesis over verified statements. · locator: ARFaceAnchor JSON; OpenUSD alembicReader.cpp L1100-L1108; UE 5.3 Live Link Face page (Wayback) Timecode Sources; UsdRender overview.md L366-L372; UsdSkel schemaOverview.dox · source: https://www.c3d.org/docs/C3D_User_Guide.pdf

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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