init latest version of harp

1 files changed, 114 insertions, 0 deletions

diff --git a/js/vendor/intersect.js b/js/vendor/intersect.js
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+++ b/js/vendor/intersect.js
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+/**
+ * @author Peter Kelley
+ * @author pgkelley4@gmail.com
+ */
+
+/**
+ * See if two line segments intersect. This uses the 
+ * vector cross product approach described below:
+ * http://stackoverflow.com/a/565282/786339
+ * 
+ * @param {Object} p point object with x and y coordinates
+ *  representing the start of the 1st line.
+ * @param {Object} p2 point object with x and y coordinates
+ *  representing the end of the 1st line.
+ * @param {Object} q point object with x and y coordinates
+ *  representing the start of the 2nd line.
+ * @param {Object} q2 point object with x and y coordinates
+ *  representing the end of the 2nd line.
+ */
+function doLineSegmentsIntersect(p, p2, q, q2) {
+	var r = subtractPoints(p2, p);
+	var s = subtractPoints(q2, q);
+
+	var uNumerator = crossProduct(subtractPoints(q, p), r);
+	var denominator = crossProduct(r, s);
+
+	if (uNumerator == 0 && denominator == 0) {
+		// They are coLlinear
+		
+		// Do they touch? (Are any of the points equal?)
+		if (equalPoints(p, q) || equalPoints(p, q2) || equalPoints(p2, q) || equalPoints(p2, q2)) {
+			return true
+		}
+		// Do they overlap? (Are all the point differences in either direction the same sign)
+		return !allEqual(
+				(q.x - p.x < 0),
+				(q.x - p2.x < 0),
+				(q2.x - p.x < 0),
+				(q2.x - p2.x < 0)) ||
+			!allEqual(
+				(q.y - p.y < 0),
+				(q.y - p2.y < 0),
+				(q2.y - p.y < 0),
+				(q2.y - p2.y < 0));
+	}
+
+	if (denominator == 0) {
+		// lines are paralell
+		return false;
+	}
+
+	var u = uNumerator / denominator;
+	var t = crossProduct(subtractPoints(q, p), s) / denominator;
+
+	return (t >= 0) && (t <= 1) && (u >= 0) && (u <= 1);
+}
+
+/**
+ * Calculate the cross product of the two points.
+ * 
+ * @param {Object} point1 point object with x and y coordinates
+ * @param {Object} point2 point object with x and y coordinates
+ * 
+ * @return the cross product result as a float
+ */
+function crossProduct(point1, point2) {
+	return point1.x * point2.y - point1.y * point2.x;
+}
+
+/**
+ * Subtract the second point from the first.
+ * 
+ * @param {Object} point1 point object with x and y coordinates
+ * @param {Object} point2 point object with x and y coordinates
+ * 
+ * @return the subtraction result as a point object
+ */ 
+function subtractPoints(point1, point2) {
+	var result = {};
+	result.x = point1.x - point2.x;
+	result.y = point1.y - point2.y;
+
+	return result;
+}
+
+/**
+ * See if the points are equal.
+ *
+ * @param {Object} point1 point object with x and y coordinates
+ * @param {Object} point2 point object with x and y coordinates
+ *
+ * @return if the points are equal
+ */
+function equalPoints(point1, point2) {
+	return (point1.x == point2.x) && (point1.y == point2.y)
+}
+
+/**
+ * See if all arguments are equal.
+ *
+ * @param {...} args arguments that will be compared by '=='.
+ *
+ * @return if all arguments are equal
+ */
+function allEqual(args) {
+	var firstValue = arguments[0],
+		i;
+	for (i = 1; i < arguments.length; i += 1) {
+		if (arguments[i] != firstValue) {
+			return false;
+		}
+	}
+	return true;
+}
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