Java examples for java.lang:Math Geometry Line
Tests if a line from point 1 to point 2 is intersecting the rectangle rect.
//package com.java2s; import java.awt.geom.Rectangle2D; public class Main { /**//from w w w . j a va 2 s . c om * Tests if a line from point 1 to point 2 is intersecting the rectangle * rect. * * @param rect * the Rectangle that maybe intersects * @param point1X * x variable of first point * @param point1Y * y variable of first point * @param point2X * x variable of second point * @param point2Y * y variable of second point * @return true if line is intersected by rect */ public static boolean recIntersectLine(Rectangle2D.Float rect, float point1X, float point1Y, float point2X, float point2Y) { return (linesIntersect(point1X, point1Y, point2X, point2Y, rect.getX(), rect.getY(), rect.getX() + rect.getWidth(), rect.getY() + rect.getHeight()) || linesIntersect(point1X, point1Y, point2X, point2Y, rect.getX(), rect.getY() + rect.getHeight(), rect.getX() + rect.getWidth(), rect.getY())); } /** * * The fastest way to test if 2 line segments intersect. Tests if the line * segment from (x1, y1) to (x2, y2) intersects the line segment from (x3, * y3) to (x4, y4). My tests showed that this method was about 25% faster * than java.awt.geom.Line2D.linesIntersect(x1, y1, x2, y2, x3, y3, x4, y4). * * NOTE: This method is taken from java-gaming.org where it was posted by * user JGO Knight. For some reason Java default intersect method as * declared in the interface Shape doesn't work. * * @param x1 * Point 1 X * @param y1 * Point 1 Y * @param x2 * Point 2 X * @param y2 * Point 2 Y * @param x3 * Point 3 X * @param y3 * Point 3 Y * @param x4 * Point 4 X * @param y4 * Point 4 Y * @return true if intersect */ private static boolean linesIntersect(double x1, double y1, double x2, double y2, double x3, double y3, double x4, double y4) { // Return false if either of the lines have zero length if (x1 == x2 && y1 == y2 || x3 == x4 && y3 == y4) { return false; } // Fastest method, based on Franklin Antonio's // "Faster Line Segment Intersection" topic "in Graphics Gems III" book // (http://www.graphicsgems.org/) double ax = x2 - x1; double ay = y2 - y1; double bx = x3 - x4; double by = y3 - y4; double cx = x1 - x3; double cy = y1 - y3; double alphaNumerator = by * cx - bx * cy; double commonDenominator = ay * bx - ax * by; if (commonDenominator > 0) { if (alphaNumerator < 0 || alphaNumerator > commonDenominator) { return false; } } else if (commonDenominator < 0) { if (alphaNumerator > 0 || alphaNumerator < commonDenominator) { return false; } } double betaNumerator = ax * cy - ay * cx; if (commonDenominator > 0) { if (betaNumerator < 0 || betaNumerator > commonDenominator) { return false; } } else if (commonDenominator < 0) { if (betaNumerator > 0 || betaNumerator < commonDenominator) { return false; } } if (commonDenominator == 0) { // This code wasn't in Franklin Antonio's method. It was added by // Keith Woodward. // The lines are parallel. // Check if they're collinear. double y3LessY1 = y3 - y1; double collinearityTestForP3 = x1 * (y2 - y3) + x2 * (y3LessY1) + x3 * (y1 - y2); // see // http://mathworld.wolfram.com/Collinear.html // If p3 is collinear with p1 and p2 then p4 will also be collinear, // since p1-p2 is parallel with p3-p4 if (collinearityTestForP3 == 0) { // The lines are collinear. Now check if they overlap. if (x1 >= x3 && x1 <= x4 || x1 <= x3 && x1 >= x4 || x2 >= x3 && x2 <= x4 || x2 <= x3 && x2 >= x4 || x3 >= x1 && x3 <= x2 || x3 <= x1 && x3 >= x2) { if (y1 >= y3 && y1 <= y4 || y1 <= y3 && y1 >= y4 || y2 >= y3 && y2 <= y4 || y2 <= y3 && y2 >= y4 || y3 >= y1 && y3 <= y2 || y3 <= y1 && y3 >= y2) { return true; } } } return false; } return true; } }