private IEnumerator RunAlgorithm(List <MyVector2> points)
{
//The list with points on the convex hull
List <MyVector2> pointsOnConvexHull = new List <MyVector2>();
//Step 0. Normalize the data to range [0, 1] or everything will break at larger sizes :(
//Make sure the data is already normalized!!!
//Step 1. Find the vertex with the smallest x coordinate
//If several points have the same x coordinate, find the one with the smallest y
MyVector2 startPos = points[0];
for (int i = 1; i < points.Count; i++)
{
MyVector2 testPos = points[i];
//Because of precision issues, we use a small value to test if they are the same
if (testPos.x < startPos.x || ((Mathf.Abs(testPos.x - startPos.x) < MathUtility.EPSILON && testPos.y < startPos.y)))
{
startPos = points[i];
}
}
//This vertex is always on the convex hull
pointsOnConvexHull.Add(startPos);
//VISUALIZE
ShowHull(pointsOnConvexHull, null);
yield return(new WaitForSeconds(controller.pauseTime));
//But we can't remove it from the list of all points because we need it to stop the algorithm
//points.Remove(startPos);
//Step 2. Loop to find the other points on the hull
MyVector2 previousPoint = pointsOnConvexHull[0];
int counter = 0;
while (true)
{
//We might have colinear points, so we need a list to save all points added this iteration
List <MyVector2> pointsToAddToTheHull = new List <MyVector2>();
//Pick next point randomly
MyVector2 nextPoint = points[Random.Range(0, points.Count)];
//If we are coming from the first point on the convex hull
//then we are not allowed to pick it as next point, so we have to try again
if (previousPoint.Equals(pointsOnConvexHull[0]) && nextPoint.Equals(pointsOnConvexHull[0]))
{
counter += 1;
continue;
}
//VISUALIZE
ShowHull(pointsOnConvexHull, new List <MyVector2>()
{
nextPoint
});
//ShowActivePoint(nextPoint);
yield return(new WaitForSeconds(controller.pauseTime));
//This point is assumed to be on the convex hull
pointsToAddToTheHull.Add(nextPoint);
//But this randomly selected point might not be the best next point, so we have to see if we can improve
//by finding a point that is more to the right
//We also have to check if this point has colinear points if it happens to be on the hull
for (int i = 0; i < points.Count; i++)
{
MyVector2 testPoint = points[i];
//Dont test the point we picked randomly
//Or the point we are coming from which might happen when we move from the first point on the hull
if (testPoint.Equals(nextPoint) || testPoint.Equals(previousPoint))
{
continue;
}
//VISUALIZE
//ShowHull(pointsOnConvexHull, new List<MyVector2>() { testPoint });
ShowActivePoint(testPoint);
yield return(new WaitForSeconds(controller.pauseTime));
//Where is the test point in relation to the line between the point we are coming from
//which we know is on the hull, and the point we think is on the hull
LeftOnRight pointRelation = _Geometry.IsPoint_Left_On_Right_OfVector(previousPoint, nextPoint, testPoint);
//The test point is on the line, so we have found a colinear point
if (pointRelation == LeftOnRight.On)
{
pointsToAddToTheHull.Add(testPoint);
}
//To the right = better point, so pick it as next point we want to test if it is on the hull
else if (pointRelation == LeftOnRight.Right)
{
nextPoint = testPoint;
//Clear colinear points because they belonged to the old point which was worse
pointsToAddToTheHull.Clear();
pointsToAddToTheHull.Add(nextPoint);
//We dont have to start over because the previous points weve gone through were worse
//VISUALIZE
ShowHull(pointsOnConvexHull, pointsToAddToTheHull);
yield return(new WaitForSeconds(controller.pauseTime));
}
//To the left = worse point so do nothing
}
//Sort this list, so we can add the colinear points in correct order
pointsToAddToTheHull = pointsToAddToTheHull.OrderBy(n => MyVector2.SqrMagnitude(n - previousPoint)).ToList();
pointsOnConvexHull.AddRange(pointsToAddToTheHull);
//Remove the points that are now on the convex hull, which should speed up the algorithm
//Or will it be slower because it also takes some time to remove points?
for (int i = 0; i < pointsToAddToTheHull.Count; i++)
{
points.Remove(pointsToAddToTheHull[i]);
}
//The point we are coming from in the next iteration
previousPoint = pointsOnConvexHull[pointsOnConvexHull.Count - 1];
//Have we found the first point on the hull? If so we have completed the hull
if (previousPoint.Equals(pointsOnConvexHull[0]))
{
//Then remove it because it is the same as the first point, and we want a convex hull with no duplicates
pointsOnConvexHull.RemoveAt(pointsOnConvexHull.Count - 1);
//Stop the loop!
break;
}
//Safety
if (counter > 100000)
{
Debug.Log("Stuck in endless loop when generating convex hull with jarvis march");
break;
}
counter += 1;
}
//Dont forget to unnormalize the points!
//VISUALIZE
ShowHull(pointsOnConvexHull, new List <MyVector2>()
{
pointsOnConvexHull[0]
});
yield return(null);
}
