KHR_gaussian_splatting

Source: https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md Status: Release Candidate (2026)

Overview

Defines basic support for storing 3D Gaussian splats in glTF assets as point cloud primitives.

Splats are defined by: position, rotation, scale, opacity, and spherical harmonics.

Extension Object Properties

Ellipse Kernel Attributes

Covariance Matrix

Σ = M·C·Cᵀ·Mᵀ

Where M = upper-left 3×3 of node transform, C = scale×rotation matrix.

Spherical Harmonics Color

Color = SH_0,0 × 0.2820947917738781 + 0.5

(plus higher degree terms for view-dependent color)

JSON Example

{
  "meshes": [{ "primitives": [{
    "attributes": {
      "POSITION": 0,
      "KHR_gaussian_splatting:SCALE": 2,
      "KHR_gaussian_splatting:ROTATION": 3,
      "KHR_gaussian_splatting:OPACITY": 4,
      "KHR_gaussian_splatting:SH_DEGREE_0_COEF_0": 5
    },
    "mode": 0,
    "extensions": {
      "KHR_gaussian_splatting": {
        "kernel": "ellipse",
        "colorSpace": "srgb_rec709_display"
      }
    }
  }]}]
}

Full Specification

See full spec at: https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_gaussian_splatting/README.md

Compression extension: KHR_gaussian_splatting_compression_spz_2

Source: https://github.com/KhronosGroup/glTF/pull/2531 Status: Draft (2026)

Extension for compressing 3D Gaussian splats using the SPZ v2 format (Niantic Spatial). Depends on KHR_gaussian_splatting above.

Usage

"extensions": {
  "KHR_gaussian_splatting": {
    "extensions": {
      "KHR_gaussian_splatting_compression_spz_2": {
        "bufferView": 0
      }
    }
  }
}

"extensionsUsed": ["KHR_gaussian_splatting", "KHR_gaussian_splatting_compression_spz_2"]

SPZ → glTF Attribute Mapping

Coordinate system: Left-Up-Front (LUF) in SPZ PackOptions/UnpackOptions for glTF compatibility.

Resources

• SPZ format: https://github.com/nianticlabs/spz
• PR: https://github.com/KhronosGroup/glTF/pull/2531

Compression extension: KHR_gaussian_splatting_compression_lgsc

Source: https://github.com/KhronosGroup/glTF/pull/2551 Status: Open PR (opened 2026-01-16, not merged) — author ibouazizi

A second, sibling compression child extension to KHR_gaussian_splatting, carrying a payload compressed with Qualcomm's L-GSC (Lite 3D Gaussian Splat Codec) v1.0. It sits at the same level in the lineage as _spz_2 above — same base extension, different codec — so the base's attribute semantics and covariance/SH math are unchanged; only the compressed blob differs.

The extension was first proposed as KHR_gaussian_splatting_lgsc and renamed during review to KHR_gaussian_splatting_compression_lgsc, a maintainer noting: "The pattern we've been using for compression extensions is KHR_gaussian_splatting_compression_lgsc." That rename is the useful signal here — Khronos is treating splat compression as an open set of interchangeable child extensions under one base, rather than blessing SPZ as the only codec.

The codec itself — qualcomm/lite-3Dgsplat-codec

Note what this implies relative to SPZ: L-GSC as published is a zlib-backed container over linearized geometry/appearance arrays with a level knob, not a fixed-bit-layout quantization scheme like SPZ v2's 24-bit positions / 3-byte rotations. The repo publishes no benchmark numbers — no compression ratios, no quality or decode-speed comparison against SPZ, SOG, or raw PLY — so any size/quality claim about L-GSC vs _spz_2 would have to be measured locally before being repeated.

Resources

• L-GSC reference codec: https://github.com/qualcomm/lite-3Dgsplat-codec
• glTF extension PR: https://github.com/KhronosGroup/glTF/pull/2551