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re-implement ConvexHull 100% original

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This commit is contained in:
OliBomby 2024-08-21 00:10:15 +02:00
parent ae47671d17
commit 09ca190b8d
1 changed files with 22 additions and 17 deletions
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39
osu.Game/Utils/GeometryUtils.cs
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@ -154,33 +154,38 @@ namespace osu.Game.Utils
{
List<Vector2> p = points.ToList();
if (p.Count <= 1)
if (p.Count < 3)
return p;
int n = p.Count, k = 0;
List<Vector2> hull = new List<Vector2>(new Vector2[2 * n]);
p.Sort((a, b) => a.X == b.X ? a.Y.CompareTo(b.Y) : a.X.CompareTo(b.X));
// Build lower hull
for (int i = 0; i < n; ++i)
List<Vector2> upper = new List<Vector2>();
List<Vector2> lower = new List<Vector2>();
// Build the lower hull
for (int i = 0; i < p.Count; i++)
{
while (k >= 2 && cross(hull[k - 2], hull[k - 1], p[i]) <= 0)
k--;
hull[k] = p[i];
k++;
while (lower.Count >= 2 && cross(lower[^2], lower[^1], p[i]) <= 0)
lower.RemoveAt(lower.Count - 1);
lower.Add(p[i]);
}
// Build upper hull
for (int i = n - 2, t = k + 1; i >= 0; i--)
// Build the upper hull
for (int i = p.Count - 1; i >= 0; i--)
{
while (k >= t && cross(hull[k - 2], hull[k - 1], p[i]) <= 0)
k--;
hull[k] = p[i];
k++;
while (upper.Count >= 2 && cross(upper[^2], upper[^1], p[i]) <= 0)
upper.RemoveAt(upper.Count - 1);
upper.Add(p[i]);
}
return hull.Take(k - 1).ToList();
// Remove the last point of each half because it's a duplicate of the first point of the other half
lower.RemoveAt(lower.Count - 1);
upper.RemoveAt(upper.Count - 1);
lower.AddRange(upper);
return lower;
float cross(Vector2 o, Vector2 a, Vector2 b) => (a.X - o.X) * (b.Y - o.Y) - (a.Y - o.Y) * (b.X - o.X);
}