Tiny Online Tools
Three levers, one number
A splat file's size is almost entirely determined by three things, and this tool puts all three in front of you with the resulting size updating live.
The splat count. File size is linear in it. Keeping the highest-contribution 60 % of a capture makes the file 40 % smaller and, on most captures, is hard to see.
The spherical-harmonic degree. Degree 3 stores 45 coefficients per splat; degree 2 stores 24, degree 1 stores 9, degree 0 none at all. Band 3 alone is 21 of those 45 — dropping it typically halves a PLY while costing far less visually than removing a comparable share of splats. It is usually the first thing to try.
The container. A PLY holding 500 000 splats at degree 3 is about 130 MB. The same splats as SPZ are around 13 MB with every band intact. As .splat they are 16 MB with no bands at all — smaller than the PLY, larger than the SPZ, and flat. The format table makes that comparison concrete.
Position precision
SPZ stores positions as fixed point. The number of fractional bits does not change the file size — three bytes per axis either way — it changes the grid positions land on and the range the format can represent. Twelve bits, the default, puts the grid at about a quarter of a millimetre, which is finer than any capture's actual accuracy.
The size is known before the work is done
The projected size follows directly from the count, the degree and the container, so it is computed instantly and nothing is recompressed while you drag. For PLY, SPLAT and KSPLAT the figure is exact — those formats are fixed-size. SPZ is gzipped, and how well a capture's data compresses varies by a factor of two between scenes, so its projection is calibrated against a real file: the capture you loaded when it is already SPZ, and the first compression otherwise.
Judge it with your eyes
A smaller file is not automatically a better file. The two viewports share a camera so you can orbit the compressed capture against the original from the same angle and decide for yourself. Everything runs in a background worker inside this page; the capture is never uploaded.