Source: shapes/GeographicMesh.js

/*
 * Copyright 2015-2017 WorldWind Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * @exports GeographicMesh
 */
define([
        '../shapes/AbstractMesh',
        '../error/ArgumentError',
        '../shaders/BasicTextureProgram',
        '../geom/BoundingBox',
        '../util/Color',
        '../util/ImageSource',
        '../geom/Location',
        '../util/Logger',
        '../geom/Matrix',
        '../pick/PickedObject',
        '../geom/Position',
        '../shapes/ShapeAttributes',
        '../shapes/SurfacePolygon',
        '../geom/Vec2',
        '../geom/Vec3',
    ],
    function (AbstractMesh,
              ArgumentError,
              BasicTextureProgram,
              BoundingBox,
              Color,
              ImageSource,
              Location,
              Logger,
              Matrix,
              PickedObject,
              Position,
              ShapeAttributes,
              SurfacePolygon,
              Vec2,
              Vec3) {
        "use strict";

        /**
         * Constructs a geographic mesh.
         * @alias GeographicMesh
         * @constructor
         * @augments AbstractMesh
         * @classdesc Represents a 3D geographic mesh.
         * <p>
         *     Altitudes within the mesh's positions are interpreted according to the mesh's altitude mode, which
         *     can be one of the following:
         * <ul>
         *     <li>[WorldWind.ABSOLUTE]{@link WorldWind#ABSOLUTE}</li>
         *     <li>[WorldWind.RELATIVE_TO_GROUND]{@link WorldWind#RELATIVE_TO_GROUND}</li>
         *     <li>[WorldWind.CLAMP_TO_GROUND]{@link WorldWind#CLAMP_TO_GROUND}</li>
         * </ul>
         * If the latter, the mesh positions' altitudes are ignored. (If the mesh should be draped onto the
         * terrain, you might want to use {@link SurfacePolygon} instead.)
         * <p>
         *     Meshes have separate attributes for normal display and highlighted display. They use the interior and
         *     outline attributes of {@link ShapeAttributes}. If those attributes identify an image, that image is
         *     applied to the mesh. Texture coordinates for the image may be specified, but if not specified the full
         *     image is stretched over the full mesh. If texture coordinates are specified, there must be one texture
         *     coordinate for each vertex in the mesh.
         *
         * @param {Position[][]} positions A two-dimensional array containing the mesh vertices.
         * Each entry of the array specifies the vertices of one row of the mesh. The arrays for all rows must
         * have the same length. There must be at least two rows, and each row must have at least two vertices.
         * There must be no more than 65536 positions.
         * @param {ShapeAttributes} attributes The attributes to associate with this mesh. May be null, in which case
         * default attributes are associated.
         *
         * @throws {ArgumentError} If the specified positions array is null or undefined, the number of rows or the
         * number of vertices per row is less than 2, the array lengths are inconsistent, or too many positions are
         * specified (limit is 65536).
         */
        var GeographicMesh = function (positions, attributes) {
            if (!positions) {
                throw new ArgumentError(
                    Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "constructor", "missingPositions"));
            }

            if (positions.length < 2 || positions[0].length < 2) {
                throw new ArgumentError(
                    Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "constructor",
                        "Number of positions is insufficient."));
            }

            // Check for size limit, which is the max number of available indices for a 16-bit unsigned int.
            if (positions.length * positions[0].length > 65536) {
                throw new ArgumentError(
                    Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "constructor",
                        "Too many positions. Must be fewer than 65536. Try using multiple meshes."));
            }

            var length = positions[0].length;
            for (var i = 1; i < positions.length; i++) {
                if (positions[i].length !== length) {
                    throw new ArgumentError(
                        Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "constructor",
                            "Array lengths are inconsistent."));
                }
            }

            var numRows = positions.length,
                numCols = positions[0].length;

            AbstractMesh.call(this, attributes);

            /**
             * Indicates whether this mesh is pickable when the pick point intersects transparent pixels of the
             * image applied to this mesh. If no image is applied to this mesh, this property is ignored. If this
             * property is true and an image with fully transparent pixels is applied to the mesh, the mesh is
             * pickable at those transparent pixels, otherwise this mesh is not pickable at those transparent pixels.
             * @type {Boolean}
             * @default true
             */
            this.pickTransparentImagePixels = true;

            // Private. Documentation is with the defined property below and the constructor description above.
            this._positions = positions;

            // Private. Documentation is with the defined property below.
            this._altitudeScale = 1;

            // Internal. Intentionally not documented.
            this.numRows = numRows;
            this.numColumns = numCols;

            // Internal. Intentionally not documented.
            this._textureCoordinates = null;

            // Internal. Intentionally not documented.
            this.referencePosition = this.determineReferencePosition(this._positions);
        };

        GeographicMesh.prototype = Object.create(AbstractMesh.prototype);

        Object.defineProperties(GeographicMesh.prototype, {
            /**
             * This mesh's positions. Each array in the positions array specifies the geographic positions of one
             * row of the mesh.
             *
             * @type {Position[][]}
             * @memberof GeographicMesh.prototype
             */
            positions: {
                get: function () {
                    return this._positions;
                },
                set: function (positions) {
                    if (!positions) {
                        throw new ArgumentError(
                            Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "positions", "missingPositions"));
                    }

                    if (positions.length < 2 || positions[0].length < 2) {
                        throw new ArgumentError(
                            Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "positions",
                                "Number of positions is insufficient."));
                    }

                    var length = positions[0].length;
                    for (var i = 1; i < positions.length; i++) {
                        if (positions[i].length !== length) {
                            throw new ArgumentError(
                                Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "positions",
                                    "Array lengths are inconsistent."));
                        }
                    }

                    this.numRows = positions.length;
                    this.numColumns = positions[0].length;

                    this._positions = positions;
                    this.referencePosition = this.determineReferencePosition(this._positions);
                    this.reset();

                    this.meshIndices = null;
                    this.outlineIndices = null;
                }
            },

            /**
             * This mesh's texture coordinates if this mesh is textured. A texture coordinate must be
             * provided for each mesh position. The texture coordinates are specified as a two-dimensional array,
             * each entry of which specifies the texture coordinates for one row of the mesh. Each texture coordinate
             * is a {@link Vec2} containing the s and t coordinates. If no texture coordinates are specified and
             * the attributes associated with this mesh indicate an image source, then texture coordinates are
             * automatically generated for the mesh.
             * @type {Vec2[][]}
             * @default null
             * @memberof GeographicMesh.prototype
             */
            textureCoordinates: {
                get: function () {
                    return this._textureCoordinates;
                },
                set: function (coords) {

                    if (coords && coords.length != this.numRows) {
                        throw new ArgumentError(
                            Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "textureCoordinates",
                                "Number of texture coordinate rows is inconsistent with the currently specified positions."));
                    }

                    for (var i = 0; i < this.numRows; i++) {
                        if (coords[i].length !== this.numColumns) {
                            throw new ArgumentError(
                                Logger.logMessage(Logger.LEVEL_SEVERE, "GeographicMesh", "textureCoordinates",
                                    "Texture coordinate row lengths are inconsistent with the currently specified positions."));
                        }
                    }

                    this._textureCoordinates = coords;
                    this.reset();
                    this.texCoords = null;
                }
            },
        });

        GeographicMesh.makeGridIndices = function (nRows, nCols) {
            // Compute indices for individual triangles.

            var gridIndices = [],
                i = 0;

            for (var r = 0; r < nRows - 1; r++) {
                for (var c = 0; c < nCols - 1; c++) {
                    var k = r * nCols + c;

                    gridIndices[i++] = k;
                    gridIndices[i++] = k + 1;
                    gridIndices[i++] = k + nCols;
                    gridIndices[i++] = k + 1;
                    gridIndices[i++] = k + 1 + nCols;
                    gridIndices[i++] = k + nCols;
                }
            }

            return gridIndices;
        };

        // Intentionally not documented.
        GeographicMesh.prototype.determineReferencePosition = function (positions) {
            // Assign the first position as the reference position.
            return positions[0][0];
        };

        // Overridden from AbstractShape base class.
        GeographicMesh.prototype.createSurfaceShape = function () {
            var boundaries = [];

            for (var c = 0; c < this.numColumns; c++) {
                boundaries.push(this._positions[0][c]);
            }

            for (var r = 1; r < this.numRows; r++) {
                boundaries.push(this._positions[r][this.numColumns - 1]);
            }

            for (c = this.numColumns - 2; c >= 0; c--) {
                boundaries.push(this._positions[this.numRows - 1][c]);
            }

            for (r = this.numRows - 2; r > 0; r--) {
                boundaries.push(this._positions[r][0]);
            }

            return new SurfacePolygon(boundaries, null);
        };

        GeographicMesh.prototype.computeMeshPoints = function (dc, currentData) {
            // Unwrap the mesh row arrays into one long array.

            var eyeDistSquared = Number.MAX_VALUE,
                eyePoint = dc.eyePoint,
                meshPoints = new Float32Array((this.numRows * this.numColumns) * 3),
                pt = new Vec3(0, 0, 0),
                k = 0,
                pos, dSquared;

            for (var r = 0; r < this._positions.length; r++) {
                for (var c = 0, len = this._positions[r].length; c < len; c++) {
                    pos = this._positions[r][c];

                    dc.surfacePointForMode(pos.latitude, pos.longitude, pos.altitude * this._altitudeScale,
                        this.altitudeMode, pt);

                    dSquared = pt.distanceToSquared(eyePoint);
                    if (dSquared < eyeDistSquared) {
                        eyeDistSquared = dSquared;
                    }

                    pt.subtract(this.currentData.referencePoint);

                    meshPoints[k++] = pt[0];
                    meshPoints[k++] = pt[1];
                    meshPoints[k++] = pt[2];
                }
            }

            currentData.eyeDistance = Math.sqrt(eyeDistSquared);

            return meshPoints;
        };

        GeographicMesh.prototype.computeTexCoords = function () {
            if (this._textureCoordinates) {
                return this.computeExplicitTexCoords();
            } else {
                return this.computeImplicitTexCoords();
            }
        };

        // Intentionally not documented.
        GeographicMesh.prototype.computeExplicitTexCoords = function () {
            // Capture the texture coordinates to a single array parallel to the mesh points array.

            var texCoords = new Float32Array(2 * this.numRows * this.numColumns),
                k = 0;

            for (var r = 0; r < this._textureCoordinates.length; r++) {
                for (var c = 0, len = this._textureCoordinates[r].length; c < len; c++) {
                    var texCoord = this._textureCoordinates[r][c];

                    texCoords[k++] = texCoord[0];
                    texCoords[k++] = texCoord[1];
                }
            }

            return texCoords;
        };

        // Intentionally not documented.
        GeographicMesh.prototype.computeImplicitTexCoords = function () {
            // Create texture coordinates that map the full image source into the full mesh.

            var texCoords = new Float32Array(2 * this.numRows * this.numColumns),
                rowDelta = 1.0 / (this.numRows - 1),
                columnDelta = 1.0 / (this.numColumns - 1),
                k = 0;

            for (var r = 0; r < this._positions.length; r++) {
                var t = (r === this.numRows - 1) ? 1.0 : r * rowDelta;

                for (var c = 0, len = this._positions[r].length; c < len; c++) {
                    texCoords[k++] = (c === this.numColumns - 1) ? 1.0 : c * columnDelta;
                    texCoords[k++] = t;
                }
            }

            return texCoords;
        };

        GeographicMesh.prototype.computeMeshIndices = function () {
            // Compute indices for individual triangles.

            var meshIndices = new Uint16Array((this.numRows - 1) * (this.numColumns - 1) * 6),
                i = 0;

            for (var r = 0; r < this.numRows - 1; r++) {
                for (var c = 0; c < this.numColumns - 1; c++) {
                    var k = r * this.numColumns + c;

                    meshIndices[i++] = k;
                    meshIndices[i++] = k + 1;
                    meshIndices[i++] = k + this.numColumns;
                    meshIndices[i++] = k + 1;
                    meshIndices[i++] = k + 1 + this.numColumns;
                    meshIndices[i++] = k + this.numColumns;
                }
            }

            return meshIndices;
        };

        GeographicMesh.prototype.computeOutlineIndices = function () {
            // Walk the mesh boundary and capture those positions for the outline.

            var outlineIndices = new Uint16Array(2 * this.numRows + 2 * this.numColumns),
                k = 0;

            for (var c = 0; c < this.numColumns; c++) {
                outlineIndices[k++] = c;
            }

            for (var r = 1; r < this.numRows; r++) {
                outlineIndices[k++] = (r + 1) * this.numColumns - 1;
            }

            for (c = this.numRows * this.numColumns - 2; c >= (this.numRows - 1) * this.numColumns; c--) {
                outlineIndices[k++] = c;
            }

            for (r = this.numRows - 2; r >= 0; r--) {
                outlineIndices[k++] = r * this.numColumns;
            }

            return outlineIndices;
        };

        return GeographicMesh;
    });