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POTranslating concave hull algorithm to c#
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  1. POTranslating concave hull algorithm to c#
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    copied!<p>So I am trying to translate the algorith found here for concave hulls: <a href="http://repositorium.sdum.uminho.pt/bitstream/1822/6429/1/ConcaveHull_ACM_MYS.pdf">http://repositorium.sdum.uminho.pt/bitstream/1822/6429/1/ConcaveHull_ACM_MYS.pdf</a></p> <p>(Page 65) </p> <p>Ive read through the entire thing but I cant figure out how to implement <code>sortByAngle</code> and <code>angle</code>, im not to sure what method I should do inside of them. This is what I have so far:</p> <pre><code>//Main method public static Vertex[] ConcaveHull(Vertex[] points, int k = 3) { if (k &lt; 3) throw new ArgumentException("K is required to be 3 or more", "k"); List&lt;Vertex&gt; hull = new List&lt;Vertex&gt;(); //Clean first, may have lots of duplicates Vertex[] clean = RemoveDuplicates(points); if (clean.Length &lt; 3) throw new ArgumentException("At least 3 dissimilar points reqired", "points"); if (clean.Length == 3)//This is the hull, its already as small as it can be. return clean; if (clean.Length &lt; k) throw new ArgumentException("K must be equal to or smaller then the amount of dissimilar points", "points"); Vertex firstPoint = clean[0]; //TODO find mid point hull.Add(firstPoint); Vertex currentPoint = firstPoint; Vertex[] dataset = RemoveIndex(clean, 0); double previousAngle = 0; int step = 2; int i; while (((currentPoint != firstPoint) || (step == 2)) &amp;&amp; (dataset.Length &gt; 0)) { if (step == 5) dataset = Add(dataset, firstPoint); Vertex[] kNearestPoints = nearestPoints(dataset, currentPoint, k); Vertex[] cPoints = sortByAngle(kNearestPoints, currentPoint, previousAngle); bool its = true; i = 0; while ((its) &amp;&amp; (i &lt; cPoints.Length)) { i++; int lastPoint = 0; if (cPoints[0] == firstPoint) lastPoint = 1; int j = 2; its = false; while ((!its) &amp;&amp; (j &lt; hull.Count - lastPoint)) { its = intersectsQ(hull[step - 1 - 1], cPoints[0], hull[step - i - j - 1], hull[step - j - 1]); j++; } } if (its) { return ConcaveHull(points, k + 1); } currentPoint = cPoints[0]; hull.Add(currentPoint); previousAngle = angle(hull[step - 1], hull[step - 2]); dataset = RemoveIndex(dataset, 0); step++; } bool allInside = true; i = dataset.Length; while (allInside &amp;&amp; i &gt; 0) { allInside = new Polygon(dataset).Contains(currentPoint); //TODO havent finished ray casting yet. i--; } if (!allInside) return ConcaveHull(points, k + 1); return hull.ToArray(); } private static Vertex[] Add(Vertex[] vs, Vertex v) { List&lt;Vertex&gt; n = new List&lt;Vertex&gt;(vs); n.Add(v); return n.ToArray(); } private static Vertex[] RemoveIndex(Vertex[] vs, int index) { List&lt;Vertex&gt; removed = new List&lt;Vertex&gt;(); for (int i = 0; i &lt; vs.Length; i++) if (i != index) removed.Add(vs[i]); return removed.ToArray(); } private static Vertex[] RemoveDuplicates(Vertex[] vs) { List&lt;Vertex&gt; clean = new List&lt;Vertex&gt;(); VertexComparer vc = new VertexComparer(); foreach (Vertex v in vs) { if (!clean.Contains(v, vc)) clean.Add(v); } return clean.ToArray(); } private static Vertex[] nearestPoints(Vertex[] vs, Vertex v, int k) { Dictionary&lt;double, Vertex&gt; lengths = new Dictionary&lt;double, Vertex&gt;(); List&lt;Vertex&gt; n = new List&lt;Vertex&gt;(); double[] sorted = lengths.Keys.OrderBy(d =&gt; d).ToArray(); for (int i = 0; i &lt; k; i++) { n.Add(lengths[sorted[i]]); } return n.ToArray(); } private static Vertex[] sortByAngle(Vertex[] vs, Vertex v, double angle) { //TODO return new Vertex[]{}; } private static bool intersectsQ(Vertex v1, Vertex v2, Vertex v3, Vertex v4) { return intersectsQ(new Edge(v1, v2), new Edge(v3, v4)); } private static bool intersectsQ(Edge e1, Edge e2) { double x1 = e1.A.X; double x2 = e1.B.X; double x3 = e2.A.X; double x4 = e2.B.X; double y1 = e1.A.Y; double y2 = e1.B.Y; double y3 = e2.A.Y; double y4 = e2.B.Y; var x = ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) / ((x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4)); var y = ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) / ((x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4)); if (double.IsNaN(x) || double.IsNaN(y)) { return false; } else { if (x1 &gt;= x2) { if (!(x2 &lt;= x &amp;&amp; x &lt;= x1)) { return false; } } else { if (!(x1 &lt;= x &amp;&amp; x &lt;= x2)) { return false; } } if (y1 &gt;= y2) { if (!(y2 &lt;= y &amp;&amp; y &lt;= y1)) { return false; } } else { if (!(y1 &lt;= y &amp;&amp; y &lt;= y2)) { return false; } } if (x3 &gt;= x4) { if (!(x4 &lt;= x &amp;&amp; x &lt;= x3)) { return false; } } else { if (!(x3 &lt;= x &amp;&amp; x &lt;= x4)) { return false; } } if (y3 &gt;= y4) { if (!(y4 &lt;= y &amp;&amp; y &lt;= y3)) { return false; } } else { if (!(y3 &lt;= y &amp;&amp; y &lt;= y4)) { return false; } } } return true; } private static double angle(Vertex v1, Vertex v2) { // TODO fix Vertex v3 = new Vertex(v1.X, 0); if (Orientation(v3, v1, v2) == 0) return 180; double b = EuclideanDistance(v3, v1); double a = EuclideanDistance(v1, v2); double c = EuclideanDistance(v3, v2); double angle = Math.Acos((Math.Pow(a, 2) + Math.Pow(b, 2) - Math.Pow(c, 2)) / (2 * a * b)); if (Orientation(v3, v1, v2) &lt; 0) angle = 360 - angle; return angle; } private static double EuclideanDistance(Vertex v1, Vertex v2) { return Math.Sqrt(Math.Pow((v1.X - v2.X), 2) + Math.Pow((v1.Y - v2.Y), 2)); } public static double Orientation(Vertex p1, Vertex p2, Vertex p) { double Orin = (p2.X - p1.X) * (p.Y - p1.Y) - (p.X - p1.X) * (p2.Y - p1.Y); if (Orin &gt; 0) return -1;//Left if (Orin &lt; 0) return 1;//Right return 0;//Colinier } </code></pre> <p>I know that there is a load of code here. But im not sure if I can show the context and what I have without it. </p> <p>Other classes:</p> <pre><code>public class Polygon { private Vertex[] vs; public Polygon(Vertex[] Vertexes) { vs = Vertexes; } public Polygon(Bounds bounds) { vs = bounds.ToArray(); } public Vertex[] ToArray() { return vs; } public IEnumerable&lt;Edge&gt; Edges() { if (vs.Length &gt; 1) { Vertex P = vs[0]; for (int i = 1; i &lt; vs.Length; i++) { yield return new Edge(P, vs[i]); P = vs[i]; } yield return new Edge(P, vs[0]); } } public bool Contains(Vertex v) { return RayCasting.RayCast(this, v); } } public class Edge { public Vertex A = new Vertex(0, 0); public Vertex B = new Vertex(0, 0); public Edge() { } public Edge(Vertex a, Vertex b) { A = a; B = b; } public Edge(double ax, double ay, double bx, double by) { A = new Vertex(ax, ay); B = new Vertex(bx, by); } } public class Bounds { public Vertex TopLeft; public Vertex TopRight; public Vertex BottomLeft; public Vertex BottomRight; public Bounds() { } public Bounds(Vertex TL, Vertex TR, Vertex BL, Vertex BR) { TopLeft = TL; TopRight = TR; BottomLeft = BL; BottomRight = BR; } public Vertex[] ToArray() { return new Vertex[] { TopLeft, TopRight, BottomRight, BottomLeft }; } } public class Vertex { public double X = 0; public double Y = 0; public Vertex() { } public Vertex(double x, double y) { X = x; Y = y; } public static Vertex[] Convert(string vs) { vs = vs.Replace("[", ""); vs = vs.Replace("]", ""); string[] spl = vs.Split(';'); List&lt;Vertex&gt; nvs = new List&lt;Vertex&gt;(); foreach (string s in spl) { try { nvs.Add(new Vertex(s)); } catch { } } return nvs.ToArray(); } public static string Stringify(Vertex[] vs) { string res = "["; foreach (Vertex v in vs) { res += v.ToString(); res += ";"; } res = res.RemoveLastCharacter(); res += "]"; return res; } public static string ToString(Vertex[] array) { string res = "["; foreach (Vertex v in array) res += v.ToString() + ","; return res.RemoveLastCharacter() + "]"; } /* //When x &lt; y return -1 //When x == y return 0 //When x &gt; y return 1 public static int Compare(Vertex x, Vertex y) { //To find lowest if (x.X &lt; y.X) { return -1; } else if (x.X == y.X) { if (x.Y &lt; y.Y) { return -1; } else if (x.Y == y.Y) { return 0; } else { return 1; } } else { return 1; } } */ public static int CompareY(Vertex a, Vertex b) { if (a.Y &lt; b.Y) return -1; if (a.Y == b.Y) return 0; return 1; } public static int CompareX(Vertex a, Vertex b) { if (a.X &lt; b.X) return -1; if (a.X == b.X) return 0; return 1; } public double distance (Vertex b){ double dX = b.X - this.X; double dY = b.Y - this.Y; return Math.Sqrt((dX*dX) + (dY*dY)); } public double slope (Vertex b){ double dX = b.X - this.X; double dY = b.Y - this.Y; return dY / dX; } public static int Compare(Vertex u, Vertex a, Vertex b) { if (a.X == b.X &amp;&amp; a.Y == b.Y) return 0; Vertex upper = new Vertex(); Vertex p1 = new Vertex(); Vertex p2 = new Vertex(); upper.X = (u.X + 180) * 360; upper.Y = (u.Y + 90) * 180; p1.X = (a.X + 180) * 360; p1.Y = (a.Y + 90) * 180; p2.X = (b.X + 180) * 360; p2.Y = (b.Y + 90) * 180; if(p1 == upper) return -1; if(p2 == upper) return 1; double m1 = upper.slope(p1); double m2 = upper.slope(p2); if (m1 == m2) { return p1.distance(upper) &lt; p2.distance(upper) ? -1 : 1; } if (m1 &lt;= 0 &amp;&amp; m2 &gt; 0) return -1; if (m1 &gt; 0 &amp;&amp; m2 &lt;= 0) return -1; return m1 &gt; m2 ? -1 : 1; } public static Vertex UpperLeft(Vertex[] vs) { Vertex top = vs[0]; for (int i = 1; i &lt; vs.Length; i++) { Vertex temp = vs[i]; if (temp.Y &gt; top.Y || (temp.Y == top.Y &amp;&amp; temp.X &lt; top.X)) { top = temp; } } return top; } } </code></pre>
 

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