Gaussian splats

A Gaussian splat is a captured scene stored as millions of soft colored ellipsoids instead of triangles: real-world places and objects with view-dependent lighting baked in. Use Spark (@sparkjsdev/spark 2.4, MIT, by World Labs): it renders splats inside the normal three.js pipeline, sorts several splat objects together, mixes them with meshes, and runs on mobile WebGL2. It needs WebGLRenderer; there is no WebGPU path.

Process

1. Get the capture into a supported format: .spz (smallest, preferred for the web), .ply (raw training output, often 50-500 MB), compressed .ply, .splat, .ksplat, or .sog. Convert large PLY files to SPZ before shipping (Spark's transcodeSpz, or the capture tool's SPZ export).
2. Read references/spark.md and set up SparkRenderer plus one SplatMesh per capture.
3. Fix orientation once: most captures come out in a y-down convention, so they appear upside down until rotated (splat.quaternion.set(1, 0, 0, 0) flips them). Set scale and position on the SplatMesh like any Object3D.
4. Wait for await splat.initialized before framing the camera or reading bounds.
5. For large scenes, turn on level of detail (lod: true on the mesh, enableLod on the renderer) and paging for multi-million-splat captures, and cap the pixel ratio; splats are fill-rate heavy.
6. Check on a phone: splat count and screen coverage decide frame rate, not file size alone.