3DTilesRendererJS/src/base/PNTSLoaderBase.js

// PNTS File Format
// https://github.com/CesiumGS/3d-tiles/blob/master/specification/TileFormats/PointCloud/README.md

import { FeatureTable, BatchTable } from "../utilities/FeatureTable.js";

export class PNTSLoaderBase {

	constructor() {

		this.fetchOptions = {};

	}

	load( url ) {

		return fetch( url, this.fetchOptions )
			.then( res => {

				if ( ! res.ok ) {

					throw new Error( `Failed to load file "${ url }" with status ${ res.status } : ${ res.statusText }` );

				}
				return res.arrayBuffer();

			} )
			.then( buffer => this.parse( buffer ) );

	}

	parse( buffer ) {

		const dataView = new DataView( buffer );

		// 28-byte header

		// 4 bytes
		const magic =
			String.fromCharCode( dataView.getUint8( 0 ) ) +
			String.fromCharCode( dataView.getUint8( 1 ) ) +
			String.fromCharCode( dataView.getUint8( 2 ) ) +
			String.fromCharCode( dataView.getUint8( 3 ) );

		console.assert( magic === 'pnts' );

		// 4 bytes
		const version = dataView.getUint32( 4, true );

		console.assert( version === 1 );

		// 4 bytes
		const byteLength = dataView.getUint32( 8, true );

		console.assert( byteLength === buffer.byteLength );

		// 4 bytes
		const featureTableJSONByteLength = dataView.getUint32( 12, true );

		// 4 bytes
		const featureTableBinaryByteLength = dataView.getUint32( 16, true );

		// 4 bytes
		const batchTableJSONByteLength = dataView.getUint32( 20, true );

		// 4 bytes
		const batchTableBinaryByteLength = dataView.getUint32( 24, true );

		// Feature Table
		const featureTableStart = 28;
		const featureTableBuffer = buffer.slice(
			featureTableStart,
			featureTableStart + featureTableJSONByteLength + featureTableBinaryByteLength,
		);
		const featureTable = new FeatureTable(
			featureTableBuffer,
			0,
			featureTableJSONByteLength,
			featureTableBinaryByteLength,
		);

		// Batch Table
		const batchTableStart = featureTableStart + featureTableJSONByteLength + featureTableBinaryByteLength;
		const batchTableBuffer = buffer.slice(
			batchTableStart,
			batchTableStart + batchTableJSONByteLength + batchTableBinaryByteLength,
		);
		const batchTable = new BatchTable(
			batchTableBuffer,
			featureTable.getData( 'BATCH_LENGTH' ) || featureTable.getData( 'POINTS_LENGTH' ),
			0,
			batchTableJSONByteLength,
			batchTableBinaryByteLength,
		);

		return {
			version,
			featureTable,
			batchTable,
		};

	}

}