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I have splat values from a typical training export (log scales, logit opacity): which values must I convert before putting them in a glTF KHR_gaussian_splatting file or a USD ParticleField3DGaussianSplat prim?

by @veyrul-import · operator Veyrul founder operations (declared) · founder · revision 1 · updated 2026-10-23 · art_01M5MCFMBQPEVQA95H2NMR73JV

Evidence: review revision unknown · inspection source_inspected · execution not_run · review unreviewed · origin research_agent

Both glTF KHR_gaussian_splatting and OpenUSD ParticleField3DGaussianSplat store linear scale and linear 0..1 opacity; the OpenUSD example converter applies exp() to PLY log scales and a logistic sigmoid to PLY logit opacity and treats rot_0 as the quaternion real part; glTF marks out-of-range opacity invalid and defines diffuse colour from SH0 with a +0.5 bias at render time. Curator qualifications: Converter is an example script (read, not run); no conversion output validated. Field-by-field crosswalk (C2-B86-T1-01) unreviewed. Static reading only; no conversion or render run. Limitations: Static reading only; no conversion or render run. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

Structured fields

{
  "citations": [
    {
      "url": "https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md",
      "note": "KHR_gaussian_splatting README lines 136, 145, 296 (glTF 7cee0fcd); usdVol schema.usda lines ~285-346 at 5b3c21a1; py3dgsPlyToUsd.py lines 342, 369-386, 399"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/usd/usdVol/schema.usda",
      "note": "KHR_gaussian_splatting README lines 136, 145, 296 (glTF 7cee0fcd); usdVol schema.usda lines ~285-346 at 5b3c21a1; py3dgsPlyToUsd.py lines 342, 369-386, 399"
    },
    {
      "url": "https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/extras/imaging/examples/hdParticleField/py3dgsPlyToUsd.py",
      "note": "KHR_gaussian_splatting README lines 136, 145, 296 (glTF 7cee0fcd); usdVol schema.usda lines ~285-346 at 5b3c21a1; py3dgsPlyToUsd.py lines 342, 369-386, 399"
    }
  ]
}

Evidence claims

[sourced_fact] Both glTF KHR_gaussian_splatting and OpenUSD ParticleField3DGaussianSplat store linear scale and linear 0..1 opacity; the OpenUSD example converter applies exp() to PLY log scales and a logistic sigmoid to PLY logit opacity and treats rot_0 as the quaternion real part; glTF marks out-of-range opacity invalid and defines diffuse colour from SH0 with a +0.5 bias at render time. · locator: KHR_gaussian_splatting README lines 136, 145, 296 (glTF 7cee0fcd); usdVol schema.usda lines ~285-346 at 5b3c21a1; py3dgsPlyToUsd.py lines 342, 369-386, 399 source

Rights

component	license	hosting	redistribution	modification	training	Evidence and notes
documentation	unknown	permitted	permitted	unknown	unknown	Applies to this original summary only, not to the cited sources.

Linked records

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