237 lines
9.0 KiB
JavaScript
237 lines
9.0 KiB
JavaScript
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/**
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* Test whether the polygon is has a positive signed area.
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* Using a y-down axis orientation, this means that the polygon is "clockwise".
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* @type {boolean}
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*/
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Object.defineProperties(PIXI.Polygon.prototype, {
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isPositive: {
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get: function() {
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if ( this._isPositive !== undefined ) return this._isPositive;
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if ( this.points.length < 6 ) return undefined;
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return this._isPositive = this.signedArea() > 0;
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}
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},
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_isPositive: {value: undefined, writable: true, enumerable: false}
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});
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/* -------------------------------------------- */
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/**
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* Clear the cached signed orientation.
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*/
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PIXI.Polygon.prototype.clearCache = function() {
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this._isPositive = undefined;
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};
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/* -------------------------------------------- */
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/**
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* Compute the signed area of polygon using an approach similar to ClipperLib.Clipper.Area.
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* The math behind this is based on the Shoelace formula. https://en.wikipedia.org/wiki/Shoelace_formula.
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* The area is positive if the orientation of the polygon is positive.
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* @returns {number} The signed area of the polygon
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*/
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PIXI.Polygon.prototype.signedArea = function() {
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const points = this.points;
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const ln = points.length;
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if ( ln < 6 ) return 0;
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// Compute area
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let area = 0;
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let x1 = points[ln - 2];
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let y1 = points[ln - 1];
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for ( let i = 0; i < ln; i += 2 ) {
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const x2 = points[i];
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const y2 = points[i + 1];
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area += (x2 - x1) * (y2 + y1);
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x1 = x2;
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y1 = y2;
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}
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// Negate the area because in Foundry canvas, y-axis is reversed
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// See https://sourceforge.net/p/jsclipper/wiki/documentation/#clipperlibclipperorientation
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// The 1/2 comes from the Shoelace formula
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return area * -0.5;
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};
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/* -------------------------------------------- */
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/**
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* Reverse the order of the polygon points in-place, replacing the points array into the polygon.
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* Note: references to the old points array will not be affected.
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* @returns {PIXI.Polygon} This polygon with its orientation reversed
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*/
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PIXI.Polygon.prototype.reverseOrientation = function() {
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const reversed_pts = [];
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const pts = this.points;
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const ln = pts.length - 2;
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for ( let i = ln; i >= 0; i -= 2 ) reversed_pts.push(pts[i], pts[i + 1]);
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this.points = reversed_pts;
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if ( this._isPositive !== undefined ) this._isPositive = !this._isPositive;
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return this;
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};
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/* -------------------------------------------- */
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/**
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* Add a de-duplicated point to the Polygon.
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* @param {Point} point The point to add to the Polygon
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* @returns {PIXI.Polygon} A reference to the polygon for method chaining
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*/
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PIXI.Polygon.prototype.addPoint = function({x, y}={}) {
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const l = this.points.length;
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if ( (x === this.points[l-2]) && (y === this.points[l-1]) ) return this;
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this.points.push(x, y);
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this.clearCache();
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return this;
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};
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/* -------------------------------------------- */
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/**
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* Return the bounding box for a PIXI.Polygon.
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* The bounding rectangle is normalized such that the width and height are non-negative.
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* @returns {PIXI.Rectangle} The bounding PIXI.Rectangle
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*/
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PIXI.Polygon.prototype.getBounds = function() {
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if ( this.points.length < 2 ) return new PIXI.Rectangle(0, 0, 0, 0);
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let maxX; let maxY;
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let minX = maxX = this.points[0];
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let minY = maxY = this.points[1];
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for ( let i=3; i<this.points.length; i+=2 ) {
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const x = this.points[i-1];
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const y = this.points[i];
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if ( x < minX ) minX = x;
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else if ( x > maxX ) maxX = x;
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if ( y < minY ) minY = y;
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else if ( y > maxY ) maxY = y;
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}
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return new PIXI.Rectangle(minX, minY, maxX - minX, maxY - minY);
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};
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/* -------------------------------------------- */
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/**
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* @typedef {Object} ClipperPoint
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* @property {number} X
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* @property {number} Y
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*/
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/**
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* Construct a PIXI.Polygon instance from an array of clipper points [{X,Y}, ...].
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* @param {ClipperPoint[]} points An array of points returned by clipper
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* @param {object} [options] Options which affect how canvas points are generated
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* @param {number} [options.scalingFactor=1] A scaling factor used to preserve floating point precision
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* @returns {PIXI.Polygon} The resulting PIXI.Polygon
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*/
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PIXI.Polygon.fromClipperPoints = function(points, {scalingFactor=1}={}) {
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const polygonPoints = [];
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for ( const point of points ) {
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polygonPoints.push(point.X / scalingFactor, point.Y / scalingFactor);
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}
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return new PIXI.Polygon(polygonPoints);
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};
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/* -------------------------------------------- */
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/**
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* Convert a PIXI.Polygon into an array of clipper points [{X,Y}, ...].
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* Note that clipper points must be rounded to integers.
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* In order to preserve some amount of floating point precision, an optional scaling factor may be provided.
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* @param {object} [options] Options which affect how clipper points are generated
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* @param {number} [options.scalingFactor=1] A scaling factor used to preserve floating point precision
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* @returns {ClipperPoint[]} An array of points to be used by clipper
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*/
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PIXI.Polygon.prototype.toClipperPoints = function({scalingFactor=1}={}) {
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const points = [];
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for ( let i = 1; i < this.points.length; i += 2 ) {
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points.push({
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X: Math.round(this.points[i-1] * scalingFactor),
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Y: Math.round(this.points[i] * scalingFactor)
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});
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}
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return points;
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};
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/* -------------------------------------------- */
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/**
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* Determine whether the PIXI.Polygon is closed, defined by having the same starting and ending point.
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* @type {boolean}
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*/
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Object.defineProperty(PIXI.Polygon.prototype, "isClosed", {
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get: function() {
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const ln = this.points.length;
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if ( ln < 4 ) return false;
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return (this.points[0] === this.points[ln-2]) && (this.points[1] === this.points[ln-1]);
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},
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enumerable: false
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});
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/* -------------------------------------------- */
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/* Intersection Methods */
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/* -------------------------------------------- */
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/**
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* Intersect this PIXI.Polygon with another PIXI.Polygon using the clipper library.
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* @param {PIXI.Polygon} other Another PIXI.Polygon
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* @param {object} [options] Options which configure how the intersection is computed
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* @param {number} [options.clipType] The clipper clip type
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* @param {number} [options.scalingFactor] A scaling factor passed to Polygon#toClipperPoints to preserve precision
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* @returns {PIXI.Polygon} The intersected polygon
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*/
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PIXI.Polygon.prototype.intersectPolygon = function(other, {clipType, scalingFactor}={}) {
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const otherPts = other.toClipperPoints({scalingFactor});
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const solution = this.intersectClipper(otherPts, {clipType, scalingFactor});
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return PIXI.Polygon.fromClipperPoints(solution.length ? solution[0] : [], {scalingFactor});
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};
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/* -------------------------------------------- */
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/**
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* Intersect this PIXI.Polygon with an array of ClipperPoints.
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* @param {ClipperPoint[]} clipperPoints Array of clipper points generated by PIXI.Polygon.toClipperPoints()
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* @param {object} [options] Options which configure how the intersection is computed
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* @param {number} [options.clipType] The clipper clip type
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* @param {number} [options.scalingFactor] A scaling factor passed to Polygon#toClipperPoints to preserve precision
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* @returns {ClipperPoint[]} The resulting ClipperPaths
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*/
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PIXI.Polygon.prototype.intersectClipper = function(clipperPoints, {clipType, scalingFactor} = {}) {
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clipType ??= ClipperLib.ClipType.ctIntersection;
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const c = new ClipperLib.Clipper();
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c.AddPath(this.toClipperPoints({scalingFactor}), ClipperLib.PolyType.ptSubject, true);
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c.AddPath(clipperPoints, ClipperLib.PolyType.ptClip, true);
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const solution = new ClipperLib.Paths();
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c.Execute(clipType, solution);
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return solution;
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};
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/* -------------------------------------------- */
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/**
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* Intersect this PIXI.Polygon with a PIXI.Circle.
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* For now, convert the circle to a Polygon approximation and use intersectPolygon.
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* In the future we may replace this with more specialized logic which uses the line-circle intersection formula.
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* @param {PIXI.Circle} circle A PIXI.Circle
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* @param {object} [options] Options which configure how the intersection is computed
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* @param {number} [options.density] The number of points which defines the density of approximation
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* @returns {PIXI.Polygon} The intersected polygon
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*/
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PIXI.Polygon.prototype.intersectCircle = function(circle, options) {
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return circle.intersectPolygon(this, options);
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};
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/* -------------------------------------------- */
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/**
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* Intersect this PIXI.Polygon with a PIXI.Rectangle.
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* For now, convert the rectangle to a Polygon and use intersectPolygon.
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* In the future we may replace this with more specialized logic which uses the line-line intersection formula.
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* @param {PIXI.Rectangle} rect A PIXI.Rectangle
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* @param {object} [options] Options which configure how the intersection is computed
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* @returns {PIXI.Polygon} The intersected polygon
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*/
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PIXI.Polygon.prototype.intersectRectangle = function(rect, options) {
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return rect.intersectPolygon(this, options);
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};
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