.PLY File Format

Introduction

The compressed PLY is a smaller way to store a Gaussian splat scene, from PlayCanvas. Its splat editor, SuperSplat, and its command line tool, splat-transform, write it, and the PlayCanvas engine loads it. It is still a valid PLY file, but its elements and properties are quite unlike those of the 3D Gaussian Splatting PLY it is made from.

Splats are taken in groups of 256, called chunks. Each chunk stores the smallest and largest position, scale and colour of its splats, and each splat stores its values as fractions of those ranges, packed into four 32-bit words. Spherical harmonics, when kept, take one byte each. A scene with degree 3 harmonics takes about a quarter of the space of the original PLY.

Structure

The header names three elements, in this order. The data is binary and little-endian.

A reader knows the layout by the chunk element and the four packed_ properties of the vertex element. Some files have only 12 floats a chunk, without the colour ranges, and the PlayCanvas decoder reads both.

In this reference

• Chunks and packing – the chunk ranges, the bit layout of each packed word and how to turn them back into a Gaussian

Also used for

• 3D Gaussian Splatting PLY – The training code’s splat layout: one float vertex a splat, 248 bytes at degree 3.
• Polygon File Format – Stanford’s mesh and point cloud format, with a header that declares every property.

Variants

• 3D Gaussian Splatting PLY – the training code’s layout: one float vertex a splat, 248 bytes at degree 3
• PlayCanvas compressed PLY – chunks of 256 splats with ranges, and four packed words a splat

Links