Line3.java

package codechicken.lib.vec;

public class Line3 {
    public static final double tol = 0.0001D;

    public Vector3 pt1;
    public Vector3 pt2;

    public Line3(Vector3 pt1, Vector3 pt2) {
        this.pt1 = pt1;
        this.pt2 = pt2;
    }

    public Line3() {
        this(new Vector3(), new Vector3());
    }

    public static boolean intersection2D(Line3 line1, Line3 line2, Vector3 store) {
        // calculate differences  
        double xD1 = line1.pt2.x - line1.pt1.x;
        double zD1 = line1.pt2.z - line1.pt1.z;
        double xD2 = line2.pt2.x - line2.pt1.x;
        double zD2 = line2.pt2.z - line2.pt1.z;

        double xD3 = line1.pt1.x - line2.pt1.x;
        double zD3 = line1.pt1.z - line2.pt1.z;

        double div = zD2 * xD1 - xD2 * zD1;
        if (div == 0)//lines are parallel
        {
            return false;
        }
        double ua = (xD2 * zD3 - zD2 * xD3) / div;
        store.set(line1.pt1.x + ua * xD1, 0, line1.pt1.z + ua * zD1);

        if (store.x >= Math.min(line1.pt1.x, line1.pt2.x) - tol && store.x >= Math.min(line2.pt1.x, line2.pt2.x) - tol && store.z >= Math.min(line1.pt1.z, line1.pt2.z) - tol && store.z >= Math.min(line2.pt1.z, line2.pt2.z) - tol && store.x <= Math.max(line1.pt1.x, line1.pt2.x) + tol && store.x <= Math.max(line2.pt1.x, line2.pt2.x) + tol && store.z <= Math.max(line1.pt1.z, line1.pt2.z) + tol && store.z <= Math.max(line2.pt1.z, line2.pt2.z) + tol) {
            return true;
        }

        return false;
    }
}