GeometryInstance.js

define([
        './defaultValue',
        './defined',
        './DeveloperError',
        './Matrix4'
    ], function(
        defaultValue,
        defined,
        DeveloperError,
        Matrix4) {
    'use strict';

    /**
     * Geometry instancing allows one {@link Geometry} object to be positions in several
     * different locations and colored uniquely.  For example, one {@link BoxGeometry} can
     * be instanced several times, each with a different <code>modelMatrix</code> to change
     * its position, rotation, and scale.
     *
     * @alias GeometryInstance
     * @constructor
     *
     * @param {Object} options Object with the following properties:
     * @param {Geometry} options.geometry The geometry to instance.
     * @param {Matrix4} [options.modelMatrix=Matrix4.IDENTITY] The model matrix that transforms to transform the geometry from model to world coordinates.
     * @param {Object} [options.id] A user-defined object to return when the instance is picked with {@link Scene#pick} or get/set per-instance attributes with {@link Primitive#getGeometryInstanceAttributes}.
     * @param {Object} [options.attributes] Per-instance attributes like a show or color attribute shown in the example below.
     *
     *
     * @example
     * // Create geometry for a box, and two instances that refer to it.
     * // One instance positions the box on the bottom and colored aqua.
     * // The other instance positions the box on the top and color white.
     * var geometry = Cesium.BoxGeometry.fromDimensions({
     *   vertexFormat : Cesium.VertexFormat.POSITION_AND_NORMAL,
     *   dimensions : new Cesium.Cartesian3(1000000.0, 1000000.0, 500000.0)
     * });
     * var instanceBottom = new Cesium.GeometryInstance({
     *   geometry : geometry,
     *   modelMatrix : Cesium.Matrix4.multiplyByTranslation(Cesium.Transforms.eastNorthUpToFixedFrame(
     *     Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883)), new Cesium.Cartesian3(0.0, 0.0, 1000000.0), new Cesium.Matrix4()),
     *   attributes : {
     *     color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.AQUA)
     *   },
     *   id : 'bottom'
     * });
     * var instanceTop = new Cesium.GeometryInstance({
     *   geometry : geometry,
     *   modelMatrix : Cesium.Matrix4.multiplyByTranslation(Cesium.Transforms.eastNorthUpToFixedFrame(
     *     Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883)), new Cesium.Cartesian3(0.0, 0.0, 3000000.0), new Cesium.Matrix4()),
     *   attributes : {
     *     color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.AQUA)
     *   },
     *   id : 'top'
     * });
     *
     * @see Geometry
     */
    function GeometryInstance(options) {
        options = defaultValue(options, defaultValue.EMPTY_OBJECT);

        //>>includeStart('debug', pragmas.debug);
        if (!defined(options.geometry)) {
            throw new DeveloperError('options.geometry is required.');
        }
        //>>includeEnd('debug');

        /**
         * The geometry being instanced.
         *
         * @type Geometry
         *
         * @default undefined
         */
        this.geometry = options.geometry;

        /**
         * The 4x4 transformation matrix that transforms the geometry from model to world coordinates.
         * When this is the identity matrix, the geometry is drawn in world coordinates, i.e., Earth's WGS84 coordinates.
         * Local reference frames can be used by providing a different transformation matrix, like that returned
         * by {@link Transforms.eastNorthUpToFixedFrame}.
         *
         * @type Matrix4
         *
         * @default Matrix4.IDENTITY
         */
        this.modelMatrix = Matrix4.clone(defaultValue(options.modelMatrix, Matrix4.IDENTITY));

        /**
         * User-defined object returned when the instance is picked or used to get/set per-instance attributes.
         *
         * @type Object
         *
         * @default undefined
         *
         * @see Scene#pick
         * @see Primitive#getGeometryInstanceAttributes
         */
        this.id = options.id;

        /**
         * Used for picking primitives that wrap geometry instances.
         *
         * @private
         */
        this.pickPrimitive = options.pickPrimitive;

        /**
         * Per-instance attributes like {@link ColorGeometryInstanceAttribute} or {@link ShowGeometryInstanceAttribute}.
         * {@link Geometry} attributes varying per vertex; these attributes are constant for the entire instance.
         *
         * @type Object
         *
         * @default undefined
         */
        this.attributes = defaultValue(options.attributes, {});

        /**
         * @private
         */
        this.westHemisphereGeometry = undefined;
        /**
         * @private
         */
        this.eastHemisphereGeometry = undefined;
    }

    return GeometryInstance;
});