MetalSplatter

MetalSplatter is a Swift and Metal library that renders 3D Gaussian splats on Apple platforms, written by Seattle developer Sean Cier and released under the MIT licence. The repository was created on December 31 2023 and carries 708 stars and 107 forks. Its package manifest targets iOS 18, macOS 15 and visionOS 2, so the library builds for iPhone, iPad, Mac and Apple Vision Pro rather than for Vision Pro alone. On Vision Pro it draws the scene in stereo using vertex amplification.

Two different things carry the MetalSplatter name and the project's own README calls the overlap confusing. The library is the open source Swift package. The MetalSplatter viewer is a separate closed source Vision Pro app built on that library, and it adds camera controls and a splat gallery the library itself does not provide. The viewer arrived for Apple Vision Pro in February 2024 and reached its own 1.0 in August 2024, while the library did not tag 1.0.0 until February 2 2026, with 1.0.1 following on February 20 2026.

The package ships four libraries and one command line tool. MetalSplatter renders a frame, PLYIO reads and writes binary and ASCII PLY files as a standalone component, SplatIO interprets PLY, SPZ and .splat files as sets of splats, and SampleBoxRenderer is a drop in replacement used for debugging an integration. The SplatConverter executable converts between the supported formats. SPZ handling comes from the separate spz-swift package, which SplatIO depends on from version 2.1.0.

One input constraint is worth knowing before a file is loaded. The PLY reader in SplatIO holds a fixed spherical harmonics count of 45 and requires every f_rest property that count implies, so it opens splat PLY files stored at the full degree three layout and rejects files written at degree one or two. A file carrying no f_rest properties at all takes a separate branch, keeps the DC term only, and loads normally. Pipelines that emit lighter files with an intermediate number of coefficients therefore produce PLY files the shipped reader will not read. A pull request opened on August 22 2026 proposes deriving the degree from the header and padding the missing coefficients with zeros, and it is unmerged.

Development is quiet. The most recent tag is 1.0.1 from February 20 2026 and the last commit on main landed on May 28 2026. Six pull requests are open, the oldest from May 2025, covering a GPU sorting implementation, a sorter loop fix, an Xcode 16.4 and Swift 6.1 build and crash fix, camera controls for the macOS and iOS sample app, a resources addition and the spherical harmonics reader change. None has a maintainer response.