{"schema":"record/v1","id":"art_01M5NE1Z7PR7G9XVNEBYR7Q8G0","type":"article","revision":1,"etag":"\"r1.s0\"","title":"Field by field, how do the ratified KHR_gaussian_splatting extension and OpenUSD's ParticleField3DGaussianSplat schema define a splat's position, rotation, scale, opacity, spherical harmonics, kernel, projection, sorting, colour space and frame, and where do they differ?","summary":"Both definitions store linear scale and linear 0..1 opacity (CA-B035), but defaults and fields differ: glTF KHR_gaussian_splatting requires a colorSpace string and defaults sortingMethod to cameraDistance, while the OpenUSD usdVol schema defaults sortingModeHint to zDepth and has no colour-space attribute, so a converter that copies defaults changes the declared sort metric and loses colour-space provenance. The glTF README carries an SPDX CC-BY-4.0 header and also a Khronos copyright statement limiting reproduction to the unmodified specification.","status":"active","body":{"text":"Both definitions store linear scale and linear 0..1 opacity (CA-B035), but defaults and fields differ: glTF KHR_gaussian_splatting requires a colorSpace string and defaults sortingMethod to cameraDistance, while the OpenUSD usdVol schema defaults sortingModeHint to zDepth and has no colour-space attribute, so a converter that copies defaults changes the declared sort metric and loses colour-space provenance. The glTF README carries an SPDX CC-BY-4.0 header and also a Khronos copyright statement limiting reproduction to the unmodified specification.\n\nCurator qualifications: Licence-scope conflict preserved: CC-BY-4.0 SPDX header vs Khronos copyright statement (unmodified reproduction, IP policy); which applies to which use is not stated. Accessor component types, SH layouts and coordinate-frame statements (F1, F2, F4, F6, F7) not re-read line by line in this batch. Static reading of the same pinned bytes used in CA-B035; nothing converted.\n\nLimitations: Static reading of the same pinned bytes used in CA-B035; nothing converted.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/schema/mesh.primitive.KHR_gaussian_splatting.schema.json","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/usd/usdVol/schema.usda","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/docs/user_guides/schemas/usdVol/ParticleField3DGaussianSplat.md","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/extras/imaging/examples/hdParticleField/py3dgsPlyToUsd.py","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"}]},"categories":["T15","T19"],"tags":[],"language":"en","visibility":"public","moderation":{"state":"visible","reason":null},"evidence":{"inspection":"source_inspected","execution":"not_run","review":"unreviewed","review_revision":null,"claims":[{"url":"https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md","claim":"Both definitions store linear scale and linear 0..1 opacity (CA-B035), but defaults and fields differ: glTF KHR_gaussian_splatting requires a colorSpace string and defaults sortingMethod to cameraDistance, while the OpenUSD usdVol schema defaults sortingModeHint to zDepth and has no colour-space attribute, so a converter that copies defaults changes the declared sort metric and loses colour-space provenance. 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The glTF README carries an SPDX CC-BY-4.0 header and also a Khronos copyright statement limiting reproduction to the unmodified specification.\n\nCurator qualifications: Licence-scope conflict preserved: CC-BY-4.0 SPDX header vs Khronos copyright statement (unmodified reproduction, IP policy); which applies to which use is not stated. Accessor component types, SH layouts and coordinate-frame statements (F1, F2, F4, F6, F7) not re-read line by line in this batch. Static reading of the same pinned bytes used in CA-B035; nothing converted.\n\nLimitations: Static reading of the same pinned bytes used in CA-B035; nothing converted.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/KhronosGroup/glTF/blob/7cee0fcddd5730e90d488bfb5aa2e52171483dde/extensions/2.0/Khronos/KHR_gaussian_splatting/schema/mesh.primitive.KHR_gaussian_splatting.schema.json","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/pxr/usd/usdVol/schema.usda","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/docs/user_guides/schemas/usdVol/ParticleField3DGaussianSplat.md","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"},{"url":"https://github.com/PixarAnimationStudios/OpenUSD/blob/5b3c21a1f20a77383fd6e7814ce6bde4e6c1895d/extras/imaging/examples/hdParticleField/py3dgsPlyToUsd.py","note":"KHR_gaussian_splatting README at 7cee0fcd, lines 2-3, 52-54, 64-92, 549-560; usdVol schema.usda at 5b3c21a1, lines 614-626"}]},"tags":[],"type":"article","links":[],"title":"Field by field, how do the ratified KHR_gaussian_splatting extension and OpenUSD's ParticleField3DGaussianSplat schema define a splat's position, rotation, scale, opacity, spherical harmonics, kernel, projection, sorting, colour space and frame, and where do they differ?","rights":[{"notes":"Applies to this original summary only, not to the cited sources.","hosting":"permitted","component":"documentation","license_id":null,"modification":"unknown","evidence_urls":[],"model_training":"unknown","redistribution":"permitted"}],"summary":"Both definitions store linear scale and linear 0..1 opacity (CA-B035), but defaults and fields differ: glTF KHR_gaussian_splatting requires a colorSpace string and defaults sortingMethod to cameraDistance, while the OpenUSD usdVol schema defaults sortingModeHint to zDepth and has no colour-space attribute, so a converter that copies defaults changes the declared sort metric and loses colour-space provenance. 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