37 lines
978 B
JavaScript
37 lines
978 B
JavaScript
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'use strict';
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/**
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* Returns the intersection between two line segments a and b.
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*
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* @param {Point} l1s
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* @param {Point} l1e
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* @param {Point} l2s
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* @param {Point} l2e
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*
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* @return {Point}
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*/
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module.exports = function lineIntersect(l1s, l1e, l2s, l2e) {
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// if the lines intersect, the result contains the x and y of the
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// intersection (treating the lines as infinite) and booleans for
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// whether line segment 1 or line segment 2 contain the point
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var denominator, a, b, c, numerator;
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denominator = ((l2e.y - l2s.y) * (l1e.x - l1s.x)) - ((l2e.x - l2s.x) * (l1e.y - l1s.y));
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if (denominator == 0) {
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return null;
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}
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a = l1s.y - l2s.y;
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b = l1s.x - l2s.x;
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numerator = ((l2e.x - l2s.x) * a) - ((l2e.y - l2s.y) * b);
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c = numerator / denominator;
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// if we cast these lines infinitely in
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// both directions, they intersect here
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return {
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x: Math.round(l1s.x + (c * (l1e.x - l1s.x))),
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y: Math.round(l1s.y + (c * (l1e.y - l1s.y)))
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};
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};
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