Which authored Gaussian-splat attributes carry through to a RenderMan render of USD, and which are lost?

In OpenUSD (ee47c679) renderers without native particle-field support get splats converted to points: the generic hdsi conversion sets point width from the mean of the three scales and turns spherical-harmonic radiance into primvars, while the hdPrman plugin replaces width with a constant 5.6; orientation and kernel are not used in either file, so the RenderMan path is a preview of positions and colour, not a faithful Gaussian splat render. Curator correction 2026-10-23 (discovery audit record C3-B642-06; sources re-fetched 2026-10-23, excerpts re-located by curator GET): Problem. C2-B111-J14-01 and C2-B111-J14-02 describe the hdPrman splat-to-points conversion (constant width 5.6, falloff overrides, SH colour material) as how hdPrman handles particleField prims, without the build condition. Conditions. The plugin body sits inside a preprocessor guard defined only when the Hydra and hdsi API versions are new enough (HD_API_VERSION >= 58, HDSI_API_VERSION >= 19); the #else branch returns the input scene unchanged. Method. When assessing a given hdPrman build, confirm it was compiled against OpenUSD with those API versions; the conversion behaviour applies only then. Failure modes. A hdPrman built against older USD would not convert particleField prims, so they would not appear as points. Limitations. The file is identical in v26.08, v26.11.0, v26.11.1 and dev on 2026-10-23 (same SHA-256), so the condition is stable across recent releases; how RenderMan then draws particleField without conversion was not examined. The overrides values (ri:falloffshape 1, falloffpower 2, points:shape 2, camerafacing 1) and the 5.6 width were confirmed. Version/date. OpenUSD ee47c67 (v26.08). Curator qualifications: Zero-fetch code reading 2026-10-22; nothing rendered. Candidate E4 phrase 'for renderers which cannot natively render the particle field' not found in the held source (may be in a header). Limitations: Zero-fetch code reading 2026-10-22; nothing rendered. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/third_party/renderman/plugin/hdPrman/particleFieldConversionSceneIndexPlugin.cpp",
      "note": "OpenUSD ee47c679 pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp L44-L66, L210, L317-L342; hdPrman particleFieldConversionSceneIndexPlugin.cpp L85-L87; usdVol schema.usda"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp",
      "note": "OpenUSD ee47c679 pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp L44-L66, L210, L317-L342; hdPrman particleFieldConversionSceneIndexPlugin.cpp L85-L87; usdVol schema.usda"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/third_party/renderman/shaders/SphericalHarmonicsToColor.osl",
      "note": "OpenUSD ee47c679 pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp L44-L66, L210, L317-L342; hdPrman particleFieldConversionSceneIndexPlugin.cpp L85-L87; usdVol schema.usda"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/usd/usdVol/schema.usda",
      "note": "OpenUSD ee47c679 pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp L44-L66, L210, L317-L342; hdPrman particleFieldConversionSceneIndexPlugin.cpp L85-L87; usdVol schema.usda"
    },
    {
      "url": "https://raw.githubusercontent.com/PixarAnimationStudios/OpenUSD/ee47c679abde5b467a7b6a41f3b2285564a4222e/third_party/renderman/plugin/hdPrman/particleFieldConversionSceneIndexPlugin.cpp",
      "note": "correction source (record C3-B642-06): lines 8-16; lines 12-14; lines 15; _AppendSceneIndex #else branch"
    }
  ]
}