Fixed the bug that boats could round over a gate but still "across" it. Added unit test to ensure the algorithm works.

tags: #story[1124]

src/main/java/seng302/model/Yacht.java

@@ -177,7 +177,7 @@ public class Yacht {
 
         if (GameState.getMarkOrder().isLastMark(currentMarkSeqID) || currentMarkSeqID == 0) {
             if (GeoUtility.checkCrossedLine(currentMark.getSubMark(1),
-                currentMark.getSubMark(2), lastLocation, location)) {
+                currentMark.getSubMark(2), lastLocation, location) > 0) {
                 System.out.println(
                     "(" + currentMarkSeqID + ") Passed gate: " + currentMark.getMarks().get(0)
                         .getName()

src/main/java/seng302/utilities/GeoUtility.java

@@ -1,10 +1,7 @@
 package seng302.utilities;
 
 import javafx.geometry.Point2D;
-import seng302.gameServer.GameState;
 import seng302.model.GeoPoint;
-import seng302.model.mark.CompoundMark;
-import seng302.model.mark.Mark;
 
 public class GeoUtility {
 
@@ -96,7 +93,6 @@ public class GeoUtility {
         return new GeoPoint(Math.toDegrees(endLat), Math.toDegrees(endLng));
     }
 
-
     /**
      * Performs the line function on two points of a line and a test point to test which side of the
      * line that point is on. If the return value is return  1, then the point is on one side of the
@@ -128,36 +124,32 @@ public class GeoUtility {
         }
     }
 
-
     /**
-     * Checks if a point passes across a line, either direction
+     * Checks if the line formed by lastLocation and location doesn't intersect the line segment
-     * See the wiki Mark Rounding algorithm for more info
+     * formed by mark1 and mark2 See the wiki Mark Rounding algorithm for more info
      *
      * @param mark1 One mark of the line
      * @param mark2 The second mark of the line
      * @param lastLocation The last location of the point crossing this line
      * @param location The current location of the point crossing this line
-     * @return True if crossed since last location --> current location, false otherwise
+     * @return 0 if two line segment doesn't intersect, otherwise 1 if they intersect and
+     * lastLocation is on RHS of the line segment (mark1 -> mark2) or 2 if lastLocation on LHS of
+     * the line segment (mark1 -> mark2)
      */
-    public static Boolean checkCrossedLine(GeoPoint mark1, GeoPoint mark2, GeoPoint lastLocation,
+    public static Integer checkCrossedLine(GeoPoint mark1, GeoPoint mark2, GeoPoint lastLocation,
         GeoPoint location) {
-        //START GATE OR FINISH GATE
+        boolean enteredDirection = isClockwise(mark1, mark2, lastLocation);
-        Double alpha = GeoUtility.getBearing(mark1, lastLocation);
+        boolean exitedDirection = isClockwise(mark1, mark2, location);
-        Double beta = GeoUtility.getBearing(mark1, mark2);
+        if (enteredDirection != exitedDirection) {
-        Double theta = GeoUtility.getBearing(mark1, location);
+            if (!isPointInTriangle(mark1, lastLocation, location, mark2)
-        alpha = (alpha > 180) ? 360 - alpha : alpha;
+                && !isPointInTriangle(mark2, lastLocation, location, mark1)) {
-        beta = (beta > 180) ? 360 - beta : beta;
-        theta = (theta > 180) ? 360 - theta : theta;
 
-        if (alpha < beta && theta > beta) {
+                return enteredDirection ? 1 : 2;
-            if (!GeoUtility.isPointInTriangle(mark1, lastLocation, location, mark2)) {
-                return true;
             }
         }
-        return false;
+        return 0;
     }
 
-
     /**
      * Given a point and a vector (angle and vector length) Will create a new point, that vector
      * away from the origin point
@@ -187,10 +179,24 @@ public class GeoUtility {
      * @param bearing2 the bearing of v2
      * @return the difference of bearing from v1 to v2
      */
-    private static double getBearingDiff(double bearing1, double bearing2) {
+    private static Double getBearingDiff(double bearing1, double bearing2) {
         return ((360 - bearing1) + bearing2) % 360;
     }
 
+    /**
+     * Check if a geo point ins on the right hand side of the line segment, which
+     * formed by two geo points v1 -> v2. (Algorithm: point is clockwise to the
+     * line if the bearing difference is less than 180 deg.)
+     *
+     * @param v1 one end of the line segment
+     * @param v2 another end of the line segment
+     * @param point the point to be tested
+     * @return true if the point is on the RHS of the line
+     */
+    private static Boolean isClockwise(GeoPoint v1, GeoPoint v2, GeoPoint point) {
+        return getBearingDiff(getBearing(v1, v2), getBearing(v1, point)) < 180;
+    }
+
     /**
      * Given three geo points to form a triangle, the method returns true if the fourth point is
      * inside the triangle
@@ -201,15 +207,15 @@ public class GeoUtility {
      * @param point the point to be tested
      * @return true if the fourth point is inside the triangle
      */
-    public static boolean isPointInTriangle(GeoPoint v1, GeoPoint v2, GeoPoint v3, GeoPoint point) {
+    public static Boolean isPointInTriangle(GeoPoint v1, GeoPoint v2, GeoPoint v3, GeoPoint point) {
         // true, if diff of bearing from (v1->v2) to (v1->p) is less than 180 deg
-        boolean sideFlag = getBearingDiff(getBearing(v1, v2), getBearing(v1, point)) < 180;
+        boolean isCW = isClockwise(v1, v2, point);
 
-        if ((getBearingDiff(getBearing(v2, v3), getBearing(v2, point)) < 180) != sideFlag) {
+        if (isClockwise(v2, v3, point) != isCW) {
             return false;
         }
 
-        if ((getBearingDiff(getBearing(v3, v1), getBearing(v3, point)) < 180) != sideFlag) {
+        if (isClockwise(v3, v1, point) != isCW) {
             return false;
         }
 

src/test/java/seng302/utilities/GeoUtilityTest.java

@@ -6,11 +6,8 @@ import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertTrue;
 
 import javafx.geometry.Point2D;
-import org.junit.Before;
 import org.junit.Test;
 import seng302.model.GeoPoint;
-import seng302.model.mark.CompoundMark;
-import seng302.utilities.GeoUtility;
 
 /**
  * http://www.geoplaner.com/ For plotting geo points for visualisation
@@ -161,13 +158,16 @@ public class GeoUtilityTest {
         GeoPoint location1 = new GeoPoint(37.40964, -122.62196);
         GeoPoint location2 = new GeoPoint(37.40910, -122.62189);
         GeoPoint location3 = new GeoPoint(37.40949, -122.62202);
-        GeoPoint location4 = new GeoPoint(34.40955, -122.62176);
+        GeoPoint location4 = new GeoPoint(37.40927, -122.62152);
-        GeoPoint location5 = new GeoPoint(37.40927, -122.62152);
-        GeoPoint location6 = new GeoPoint(34.40933, -122.62163);
 
-        assertTrue(GeoUtility.checkCrossedLine(mark1, mark2, location1, location2));
+        // M1 -> M3 enters from CCW side
-        assertFalse(GeoUtility.checkCrossedLine(mark1, mark2, location4, location3));
+        assertTrue(GeoUtility.checkCrossedLine(mark1, mark2, location1, location2) == 2);
-        assertFalse(GeoUtility.checkCrossedLine(mark1, mark2, location1, location3));
+        // M1 -> M3 doesn't across
-        assertFalse(GeoUtility.checkCrossedLine(mark1, mark2, location5, location6));
+        assertFalse(GeoUtility.checkCrossedLine(mark1, mark2, location1, location3) > 0);
+        // M2 -> M3 enters from CW side
+        assertTrue(GeoUtility.checkCrossedLine(mark1, mark2, location2, location3) == 1);
+        // order changes intersect direction
+        assertTrue(GeoUtility.checkCrossedLine(mark2, mark1, location2, location3) == 2);
+        assertTrue(GeoUtility.checkCrossedLine(mark1, mark2, location3, location2) == 2);
     }
 }