segments Intersection - Android java.lang

Android examples for java.lang:Math

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Description

segments Intersection

Demo Code


import java.util.Vector;
import android.graphics.PointF;

public class Main{
    /**//from www.ja v a 2 s. c  o  m
     * 
     * http://alienryderflex.com/intersect/
     * 
     * @param a0x
     * @param a0y
     * @param a1x
     * @param a1y
     * @param b0x
     * @param b0y
     * @param b1x
     * @param b1y
     * @return Intersecci?n entre dos segmentos
     */
    public static PointF segmentsIntersection(float a0x, float a0y,
            float a1x, float a1y, float b0x, float b0y, float b1x, float b1y) {

        float distA, theCos, theSin, newX, aPos;

        // Fail if either line segment is zero-length.
        if (a0x == a1x && a0y == a1y || b0x == b1x && b0y == b1y) {
            return null;
        }

        // Fail if the segments share an end-point.
        if (a0x == b0x && a0y == b0y || a1x == b0x && a1y == b0y
                || a0x == b1x && a0y == b1y || a1x == b1x && a1y == b1y) {
            return null;
        }

        // (1) Translate the system so that point a0 is on the origin.
        a1x -= a0x;
        a1y -= a0y;
        b0x -= a0x;
        b0y -= a0y;
        b1x -= a0x;
        b1y -= a0y;

        // Discover the length of segment a0 - a1
        distA = MathUtils.getDistance(a1x, a1y);

        // (2) Rotate the system so that point a1 is on the positive X axis.
        theCos = a1x / distA;
        theSin = a1y / distA;
        newX = b0x * theCos + b0y * theSin;
        b0y = b0y * theCos - b0x * theSin;
        b0x = newX;
        newX = b1x * theCos + b1y * theSin;
        b1y = b1y * theCos - b1x * theSin;
        b1x = newX;

        // Fail if segment b0-b1 doesn't cross line a0-a1
        if (b0y < 0 && b1y < 0 || b0y >= 0 && b1y >= 0) {
            return null;
        }

        // (3) Discover the position of the intersection point along line a0-a1
        aPos = b1x + (b0x - b1x) * b1y / (b1y - b0y);

        // Fail if segment b0-b1 crosses line a0-a1 outside of segment a0-a1
        if (aPos < 0 || aPos > distA) {
            return null;
        }

        // (4) Apply the discovered position to line a0-a1 in the original
        // coordinate system.
        // Success.
        return new PointF(a0x + aPos * theCos, a0y + aPos * theSin);
    }
    /**
     * @param x0
     * @param y0
     * @param x1
     * @param y1
     * @return distancia entre dos puntos
     */
    public static float getDistance(float x0, float y0, float x1, float y1) {
        return getDistance(x1 - x0, y1 - y0);
    }
    /**
     * @param side0
     * @param side1
     * @return distancia entre dos puntos en la misma recta
     */
    public static float getDistance(float side0, float side1) {
        return (float) Math.sqrt(side0 * side0 + side1 * side1);
    }
}

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