cesium/Source/Workers/createVectorTilePoints.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

define([
        '../Core/AttributeCompression',
        '../Core/Cartesian3',
        '../Core/Cartographic',
        '../Core/Ellipsoid',
        '../Core/Math',
        '../Core/Rectangle',
        './createTaskProcessorWorker'
    ], function(
        AttributeCompression,
        Cartesian3,
        Cartographic,
        Ellipsoid,
        CesiumMath,
        Rectangle,
        createTaskProcessorWorker) {
    'use strict';

    var maxShort = 32767;

    var scratchBVCartographic = new Cartographic();
    var scratchEncodedPosition = new Cartesian3();

    var scratchRectangle = new Rectangle();
    var scratchEllipsoid = new Ellipsoid();
    var scratchMinMaxHeights = {
        min : undefined,
        max : undefined
    };

    function unpackBuffer(packedBuffer) {
        packedBuffer = new Float64Array(packedBuffer);

        var offset = 0;
        scratchMinMaxHeights.min = packedBuffer[offset++];
        scratchMinMaxHeights.max = packedBuffer[offset++];

        Rectangle.unpack(packedBuffer, offset, scratchRectangle);
        offset += Rectangle.packedLength;

        Ellipsoid.unpack(packedBuffer, offset, scratchEllipsoid);
    }

    function createVectorTilePoints(parameters, transferableObjects) {
        var positions = new Uint16Array(parameters.positions);

        unpackBuffer(parameters.packedBuffer);
        var rectangle = scratchRectangle;
        var ellipsoid = scratchEllipsoid;
        var minimumHeight = scratchMinMaxHeights.min;
        var maximumHeight = scratchMinMaxHeights.max;

        var positionsLength = positions.length / 3;
        var uBuffer = positions.subarray(0, positionsLength);
        var vBuffer = positions.subarray(positionsLength, 2 * positionsLength);
        var heightBuffer = positions.subarray(2 * positionsLength, 3 * positionsLength);
        AttributeCompression.zigZagDeltaDecode(uBuffer, vBuffer, heightBuffer);

        var decoded = new Float64Array(positions.length);
        for (var i = 0; i < positionsLength; ++i) {
            var u = uBuffer[i];
            var v = vBuffer[i];
            var h = heightBuffer[i];

            var lon = CesiumMath.lerp(rectangle.west, rectangle.east, u / maxShort);
            var lat = CesiumMath.lerp(rectangle.south, rectangle.north, v / maxShort);
            var alt = CesiumMath.lerp(minimumHeight, maximumHeight, h / maxShort);

            var cartographic = Cartographic.fromRadians(lon, lat, alt, scratchBVCartographic);
            var decodedPosition = ellipsoid.cartographicToCartesian(cartographic, scratchEncodedPosition);
            Cartesian3.pack(decodedPosition, decoded, i * 3);
        }

        transferableObjects.push(decoded.buffer);

        return {
            positions : decoded.buffer
        };
    }

    return createTaskProcessorWorker(createVectorTilePoints);
});