Data update

Task/Find-if-a-point-is-within-a-triangle/JavaScript/find-if-a-point-is-within-a-triangle.js

@@ -0,0 +1,109 @@
+const EPS = 0.001;
+const EPS_SQUARE = EPS * EPS;
+
+function side(x1, y1, x2, y2, x, y) {
+	return (y2 - y1) * (x - x1) + (-x2 + x1) * (y - y1);
+}
+
+function naivePointInTriangle(x1, y1, x2, y2, x3, y3, x, y) {
+	const checkSide1 = side(x1, y1, x2, y2, x, y) >= 0;
+	const checkSide2 = side(x2, y2, x3, y3, x, y) >= 0;
+	const checkSide3 = side(x3, y3, x1, y1, x, y) >= 0;
+	return checkSide1 && checkSide2 && checkSide3;
+}
+
+function pointInTriangleBoundingBox(x1, y1, x2, y2, x3, y3, x, y) {
+	const xMin = Math.min(x1, Math.min(x2, x3)) - EPS;
+	const xMax = Math.max(x1, Math.max(x2, x3)) + EPS;
+	const yMin = Math.min(y1, Math.min(y2, y3)) - EPS;
+	const yMax = Math.max(y1, Math.max(y2, y3)) + EPS;
+	return !(x < xMin || xMax < x || y < yMin || yMax < y);
+}
+
+function distanceSquarePointToSegment(x1, y1, x2, y2, x, y) {
+	const p1_p2_squareLength = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
+	const dotProduct =
+		((x - x1) * (x2 - x1) + (y - y1) * (y2 - y1)) / p1_p2_squareLength;
+	if (dotProduct < 0) {
+		return (x - x1) * (x - x1) + (y - y1) * (y - y1);
+	} else if (dotProduct <= 1) {
+		const p_p1_squareLength = (x1 - x) * (x1 - x) + (y1 - y) * (y1 - y);
+		return p_p1_squareLength - dotProduct * dotProduct * p1_p2_squareLength;
+	} else {
+		return (x - x2) * (x - x2) + (y - y2) * (y - y2);
+	}
+}
+
+function accuratePointInTriangle(x1, y1, x2, y2, x3, y3, x, y) {
+	if (!pointInTriangleBoundingBox(x1, y1, x2, y2, x3, y3, x, y)) {
+		return false;
+	}
+	if (naivePointInTriangle(x1, y1, x2, y2, x3, y3, x, y)) {
+		return true;
+	}
+	if (distanceSquarePointToSegment(x1, y1, x2, y2, x, y) <= EPS_SQUARE) {
+		return true;
+	}
+	if (distanceSquarePointToSegment(x2, y2, x3, y3, x, y) <= EPS_SQUARE) {
+		return true;
+	}
+	if (distanceSquarePointToSegment(x3, y3, x1, y1, x, y) <= EPS_SQUARE) {
+		return true;
+	}
+	return false;
+}
+
+function printPoint(x, y) {
+	return "(" + x + ", " + y + ")";
+}
+
+function printTriangle(x1, y1, x2, y2, x3, y3) {
+	return (
+		"Triangle is [" +
+		printPoint(x1, y1) +
+		", " +
+		printPoint(x2, y2) +
+		", " +
+		printPoint(x3, y3) +
+		"]"
+	);
+}
+
+function test(x1, y1, x2, y2, x3, y3, x, y) {
+	console.log(
+		printTriangle(x1, y1, x2, y2, x3, y3) +
+		"Point " +
+		printPoint(x, y) +
+		" is within triangle? " +
+		(accuratePointInTriangle(x1, y1, x2, y2, x3, y3, x, y) ? "true" : "false")
+	);
+}
+
+test(1.5, 2.4, 5.1, -3.1, -3.8, 1.2, 0, 0);
+test(1.5, 2.4, 5.1, -3.1, -3.8, 1.2, 0, 1);
+test(1.5, 2.4, 5.1, -3.1, -3.8, 1.2, 3, 1);
+console.log();
+
+test(
+	0.1,
+	0.1111111111111111,
+	12.5,
+	33.333333333333336,
+	25,
+	11.11111111111111,
+	5.414285714285714,
+	14.349206349206348
+);
+console.log();
+
+test(
+	0.1,
+	0.1111111111111111,
+	12.5,
+	33.333333333333336,
+	-12.5,
+	16.666666666666668,
+	5.414285714285714,
+	14.349206349206348
+);
+console.log();