# What changed in OpenUSD's Gaussian-splat particle-field path between v26.08 and v26.11.0, and does any renderer path now use the sorting or projection hints?

- id: art_01M5ME67D44CB47MA9DJ8EP8N4
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T15, T19 · tags: none
- updated: 2026-10-23T13:11:17.151Z
- url: https://veyrul.com/articles/art_01M5ME67D44CB47MA9DJ8EP8N4

At v26.11.0 usdImaging exports a Hydra particleField container with kernelType (hardcoded gaussianEllipsoid) and both hints, closing the v26.08 TODO; the new hd schema exposes only kernelType, and the hdsi conversion, hdPrman plugin, sample renderer and schema.usda are byte-identical to v26.08, so by code reading none of them consumes the hints.

At v26.11.0 usdImaging exports a Hydra particleField container with kernelType (hardcoded gaussianEllipsoid) and both hints, closing the v26.08 TODO; the new hd schema exposes only kernelType, and the hdsi conversion, hdPrman plugin, sample renderer and schema.usda are byte-identical to v26.08, so by code reading none of them consumes the hints.

Curator qualifications: Code read at three tags 2026-10-22; not built or run (code reading, not execution). plugInfo.json and tree-diff (S10, S11) not re-checked.

Limitations: Code read at three tags 2026-10-22; not built or run (code reading, not execution).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/usdImaging/usdVolImaging/dataSourceParticleField.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/third_party/renderman/plugin/hdPrman/plugInfo.json",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://api.github.com/repos/PixarAnimationStudios/OpenUSD/git/trees/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d?recursive=1",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/usdImaging/usdVolImaging/dataSourceParticleField.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/imaging/hd/particleFieldSchema.h",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/imaging/hd/particleFieldSchema.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/imaging/hdsi/particleFieldConversionSceneIndex.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/third_party/renderman/plugin/hdPrman/particleFieldConversionSceneIndexPlugin.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/extras/imaging/examples/hdParticleField/gsRenderer.cpp",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/docs/user_guides/schemas/usdVol/ParticleField3DGaussianSplat.md",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/usd/usdVol/schema.usda",
      "note": "dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] At v26.11.0 usdImaging exports a Hydra particleField container with kernelType (hardcoded gaussianEllipsoid) and both hints, closing the v26.08 TODO; the new hd schema exposes only kernelType, and the hdsi conversion, hdPrman plugin, sample renderer and schema.usda are byte-identical to v26.08, so by code reading none of them consumes the hints. · locator: dataSourceParticleField.cpp at v26.11.0 (raw), L93-118; imaging/hd/particleFieldSchema.h at v26.11.0; curator sha256 comparison across tags · source: https://github.com/PixarAnimationStudios/OpenUSD/blob/ee47c679abde5b467a7b6a41f3b2285564a4222e/pxr/usdImaging/usdVolImaging/dataSourceParticleField.cpp

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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