@voxelkloud/format-ept

The Entwine Point Tile driver for voxelkloud.

npm install @voxelkloud/format-ept

import { eptFormat } from "@voxelkloud/format-ept";
import { formats, loadPointCloud } from "@voxelkloud/loader";

formats.register(eptFormat);

const { source, tree, openPoints } = await loadPointCloud(
  "https://s3.amazonaws.com/example/ept-dataset/",
);
view.addCloud(source, tree, openPoints);

NOT registered by default: a laszip dataset needs the wasm LAZ decoder, and an app that reads neither EPT nor COPC should not carry it.

What it is

A directory of static files: one ept.json, a hierarchy of JSON pages, one payload per node. No Range support required of the host — which is why the USGS 3DEP archive on S3 is published this way, and why pasting one of its URLs is the shortest path from nothing to a rendered LiDAR survey.

Three payload encodings, all supported:

| dataType | Payload | Needs | | --- | --- | --- | | binary | the schema packed interleaved | nothing | | laszip | a whole LAS file per node | the wasm LAZ decoder | | zstandard | a zstd-compressed binary block | a decompress hook |

No browser exposes zstd to JavaScript, so a zstandard dataset needs a decompressor supplied from outside — the same hook a BROTLI Potree cloud uses:

openPoints({ decompress: (bytes) => myZstd.decode(bytes) });

Without one the error names the hook rather than failing obscurely.

The one surprise

For laszip, the manifest's schema and the LAS records Entwine actually writes disagree. Its schema calls ScanAngleRank a 4-byte float; the LAS record it writes stores a signed byte. So the driver reads the root node's own LAS header at load time and believes that instead — one extra request, and not avoidable. For binary and zstandard the schema is the only description there is, and it is correct.

Attribute names

EPT writes "Intensity", "ReturnNumber", "GpsTime". Every other driver here writes "intensity", "return number", "gps-time", and a colour mode must not stop working because the cloud was published as EPT — so the names are translated. X/Y/Z become one "position" attribute and Red/Green/Blue one "rgb"; a dimension with no counterpart, like Entwine's OriginId, keeps its own spelling.

Testing

demo/potree/pointclouds/ holds the same cloud built four ways — binary, laszip in LAS 1.2, laszip in LAS 1.4, and zstandard. That is a better oracle than any of them alone: two encodings of one dataset must decode to the same points, and only one of them can be wrong at a time. The suite compares all 35,091 points of the root node field for field, as sets rather than in order, because Entwine does not promise a within-node ordering across separate builds.

Those files are gitignored, and the suite skips itself when they are absent.

MIT.