48 lines
1.7 KiB
JavaScript
48 lines
1.7 KiB
JavaScript
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// Copyright (c) 2011, Chris Umbel, James Coglan
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// Polygon.Vertex class - required for Polygon class.
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var Sylvester = require('./sylvester');
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Polygon.Vertex = function(point) {
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this.setElements(point);
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if (this.elements.length == 2) { this.elements.push(0); }
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if (this.elements.length != 3) { return null; }
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};
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Polygon.Vertex.prototype = new Vector;
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// Returns true iff the vertex's internal angle is 0 <= x < 180
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// in the context of the given polygon object. Returns null if the
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// vertex does not exist in the polygon.
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Polygon.Vertex.prototype.isConvex = function(polygon) {
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var node = polygon.nodeFor(this);
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if (node === null) { return null; }
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var prev = node.prev.data, next = node.next.data;
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var A = next.subtract(this);
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var B = prev.subtract(this);
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var theta = A.angleFrom(B);
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if (theta <= Sylvester.precision) { return true; }
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if (Math.abs(theta - Math.PI) <= Sylvester.precision) { return false; }
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return (A.cross(B).dot(polygon.plane.normal) > 0);
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};
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// Returns true iff the vertex's internal angle is 180 <= x < 360
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Polygon.Vertex.prototype.isReflex = function(polygon) {
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var result = this.isConvex(polygon);
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return (result === null) ? null : !result;
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};
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Polygon.Vertex.prototype.type = function(polygon) {
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var result = this.isConvex(polygon);
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return (result === null) ? null : (result ? 'convex' : 'reflex');
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};
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// Method for converting a set of arrays/vectors/whatever to a set of Polygon.Vertex objects
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Polygon.Vertex.convert = function(points) {
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var pointSet = points.toArray ? points.toArray() : points;
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var list = [], n = pointSet.length;
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for (var i = 0; i < n; i++) {
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list.push(new Polygon.Vertex(pointSet[i]));
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}
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return list;
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};
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module.exports = Polygon.Vertex;
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