@cesium/engine
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CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.
246 lines (219 loc) • 8.19 kB
JavaScript
import Cartesian2 from "./Cartesian2.js";
import Check from "./Check.js";
import Frozen from "./Frozen.js";
import defined from "./defined.js";
import Ellipsoid from "./Ellipsoid.js";
import GeographicProjection from "./GeographicProjection.js";
import CesiumMath from "./Math.js";
import Rectangle from "./Rectangle.js";
/**
* A tiling scheme for geometry referenced to a simple {@link GeographicProjection} where
* longitude and latitude are directly mapped to X and Y. This projection is commonly
* known as geographic, equirectangular, equidistant cylindrical, or plate carrée.
*
* @alias GeographicTilingScheme
* @constructor
*
* @param {object} [options] Object with the following properties:
* @param {Ellipsoid} [options.ellipsoid=Ellipsoid.default] The ellipsoid whose surface is being tiled. Defaults to
* the default ellipsoid.
* @param {Rectangle} [options.rectangle=Rectangle.MAX_VALUE] The rectangle, in radians, covered by the tiling scheme.
* @param {number} [options.numberOfLevelZeroTilesX=2] The number of tiles in the X direction at level zero of
* the tile tree.
* @param {number} [options.numberOfLevelZeroTilesY=1] The number of tiles in the Y direction at level zero of
* the tile tree.
*/
function GeographicTilingScheme(options) {
options = options ?? Frozen.EMPTY_OBJECT;
this._ellipsoid = options.ellipsoid ?? Ellipsoid.default;
this._rectangle = options.rectangle ?? Rectangle.MAX_VALUE;
this._projection = new GeographicProjection(this._ellipsoid);
this._numberOfLevelZeroTilesX = options.numberOfLevelZeroTilesX ?? 2;
this._numberOfLevelZeroTilesY = options.numberOfLevelZeroTilesY ?? 1;
}
Object.defineProperties(GeographicTilingScheme.prototype, {
/**
* Gets the ellipsoid that is tiled by this tiling scheme.
* @memberof GeographicTilingScheme.prototype
* @type {Ellipsoid}
*/
ellipsoid: {
get: function () {
return this._ellipsoid;
},
},
/**
* Gets the rectangle, in radians, covered by this tiling scheme.
* @memberof GeographicTilingScheme.prototype
* @type {Rectangle}
*/
rectangle: {
get: function () {
return this._rectangle;
},
},
/**
* Gets the map projection used by this tiling scheme.
* @memberof GeographicTilingScheme.prototype
* @type {MapProjection}
*/
projection: {
get: function () {
return this._projection;
},
},
});
/**
* Gets the total number of tiles in the X direction at a specified level-of-detail.
*
* @param {number} level The level-of-detail.
* @returns {number} The number of tiles in the X direction at the given level.
*/
GeographicTilingScheme.prototype.getNumberOfXTilesAtLevel = function (level) {
return this._numberOfLevelZeroTilesX << level;
};
/**
* Gets the total number of tiles in the Y direction at a specified level-of-detail.
*
* @param {number} level The level-of-detail.
* @returns {number} The number of tiles in the Y direction at the given level.
*/
GeographicTilingScheme.prototype.getNumberOfYTilesAtLevel = function (level) {
return this._numberOfLevelZeroTilesY << level;
};
/**
* Transforms a rectangle specified in geodetic radians to the native coordinate system
* of this tiling scheme.
*
* @param {Rectangle} rectangle The rectangle to transform.
* @param {Rectangle} [result] The instance to which to copy the result, or undefined if a new instance
* should be created.
* @returns {Rectangle} The specified 'result', or a new object containing the native rectangle if 'result'
* is undefined.
*/
GeographicTilingScheme.prototype.rectangleToNativeRectangle = function (
rectangle,
result,
) {
//>>includeStart('debug', pragmas.debug);
Check.defined("rectangle", rectangle);
//>>includeEnd('debug');
const west = CesiumMath.toDegrees(rectangle.west);
const south = CesiumMath.toDegrees(rectangle.south);
const east = CesiumMath.toDegrees(rectangle.east);
const north = CesiumMath.toDegrees(rectangle.north);
if (!defined(result)) {
return new Rectangle(west, south, east, north);
}
result.west = west;
result.south = south;
result.east = east;
result.north = north;
return result;
};
/**
* Converts tile x, y coordinates and level to a rectangle expressed in the native coordinates
* of the tiling scheme.
*
* @param {number} x The integer x coordinate of the tile.
* @param {number} y The integer y coordinate of the tile.
* @param {number} level The tile level-of-detail. Zero is the least detailed.
* @param {object} [result] The instance to which to copy the result, or undefined if a new instance
* should be created.
* @returns {Rectangle} The specified 'result', or a new object containing the rectangle
* if 'result' is undefined.
*/
GeographicTilingScheme.prototype.tileXYToNativeRectangle = function (
x,
y,
level,
result,
) {
const rectangleRadians = this.tileXYToRectangle(x, y, level, result);
rectangleRadians.west = CesiumMath.toDegrees(rectangleRadians.west);
rectangleRadians.south = CesiumMath.toDegrees(rectangleRadians.south);
rectangleRadians.east = CesiumMath.toDegrees(rectangleRadians.east);
rectangleRadians.north = CesiumMath.toDegrees(rectangleRadians.north);
return rectangleRadians;
};
/**
* Converts tile x, y coordinates and level to a cartographic rectangle in radians.
*
* @param {number} x The integer x coordinate of the tile.
* @param {number} y The integer y coordinate of the tile.
* @param {number} level The tile level-of-detail. Zero is the least detailed.
* @param {object} [result] The instance to which to copy the result, or undefined if a new instance
* should be created.
* @returns {Rectangle} The specified 'result', or a new object containing the rectangle
* if 'result' is undefined.
*/
GeographicTilingScheme.prototype.tileXYToRectangle = function (
x,
y,
level,
result,
) {
const rectangle = this._rectangle;
const xTiles = this.getNumberOfXTilesAtLevel(level);
const yTiles = this.getNumberOfYTilesAtLevel(level);
const xTileWidth = rectangle.width / xTiles;
const west = x * xTileWidth + rectangle.west;
const east = (x + 1) * xTileWidth + rectangle.west;
const yTileHeight = rectangle.height / yTiles;
const north = rectangle.north - y * yTileHeight;
const south = rectangle.north - (y + 1) * yTileHeight;
if (!defined(result)) {
result = new Rectangle(west, south, east, north);
}
result.west = west;
result.south = south;
result.east = east;
result.north = north;
return result;
};
/**
* Calculates the tile x, y coordinates of the tile containing
* a given cartographic position.
*
* @param {Cartographic} position The position.
* @param {number} level The tile level-of-detail. Zero is the least detailed.
* @param {Cartesian2} [result] The instance to which to copy the result, or undefined if a new instance
* should be created.
* @returns {Cartesian2} The specified 'result', or a new object containing the tile x, y coordinates
* if 'result' is undefined.
*/
GeographicTilingScheme.prototype.positionToTileXY = function (
position,
level,
result,
) {
const rectangle = this._rectangle;
if (!Rectangle.contains(rectangle, position)) {
// outside the bounds of the tiling scheme
return undefined;
}
const xTiles = this.getNumberOfXTilesAtLevel(level);
const yTiles = this.getNumberOfYTilesAtLevel(level);
const xTileWidth = rectangle.width / xTiles;
const yTileHeight = rectangle.height / yTiles;
let longitude = position.longitude;
if (rectangle.east < rectangle.west) {
longitude += CesiumMath.TWO_PI;
}
let xTileCoordinate = ((longitude - rectangle.west) / xTileWidth) | 0;
if (xTileCoordinate >= xTiles) {
xTileCoordinate = xTiles - 1;
}
let yTileCoordinate =
((rectangle.north - position.latitude) / yTileHeight) | 0;
if (yTileCoordinate >= yTiles) {
yTileCoordinate = yTiles - 1;
}
if (!defined(result)) {
return new Cartesian2(xTileCoordinate, yTileCoordinate);
}
result.x = xTileCoordinate;
result.y = yTileCoordinate;
return result;
};
export default GeographicTilingScheme;