// Return the points that make up a polygon's convex hull.
// This method leaves the points list unchanged.
public static List <Point> MakeConvexHull(List <Point> points)
{
var convexHull = new ConvexHull(points);
convexHull.CalcConvexHull(ConvexHullThreadUsage.OnlyOne);
return(convexHull.GetResultsAsArrayOfPoint().ToList());
}
/// <summary>
/// Using algorithm from Ouellet - https://www.codeproject.com/Articles/1210225/Fast-and-improved-D-Convex-Hull-algorithm-and-its, take an IEnumerable of Point2Ds and computes the
/// two dimensional convex hull, returning it as a Polygon2D object.
/// </summary>
/// <param name="pointList">A list of points</param>
/// <param name="clockWise">
/// In which direction to return the points on the convex hull.
/// If true, clockwise. Otherwise counter clockwise
/// </param>
/// <returns>A polygon.</returns>
public static Polygon2D GetConvexHullFromPoints(IEnumerable <Point2D> pointList, bool clockWise = true)
{
int count = pointList.Count();
// Perform basic validation of the input point cloud for cases of less than
// four points being given
if (count <= 2)
{
throw new ArgumentException("Must have at least 3 points in the polygon to compute the convex hull");
}
if (count <= 3)
{
return(new Polygon2D(pointList));
}
var chull = new ConvexHull(pointList, false);
chull.CalcConvexHull();
var hullPoints = chull.GetResultsAsArrayOfPoint();
// Order the hull points by angle to the centroid
var centroid = Point2D.Centroid(hullPoints);
var xAxis = new Vector2D(1, 0);
var results = (from x in hullPoints select new Tuple <Angle, Point2D>(centroid.VectorTo(x).SignedAngleTo(xAxis, clockWise), x)).ToList();
results.Sort((a, b) => a.Item1.CompareTo(b.Item1));
return(new Polygon2D(from x in results select x.Item2));
}
/// <summary>
/// Join two separated polygons together
/// <see href="https://stackoverflow.com/questions/18619117/combine-nearby-polygons"/>
/// Using a port of @brianmearns answer
/// </summary>
public static List <SKPoint> JoinPolygon(List <SKPoint> polygon1, List <SKPoint> polygon2)
{
ConvexHull convexHull = new ConvexHull();
convexHull.CalcConvexHull(new List <SKPoint>().Concat(polygon1).Concat(polygon2).ToList().AsReadOnly());
SKPoint[] points = convexHull.GetResultsAsArrayOfPoint();
Debug.Print(points.ToString());
List <SKPoint> finalPolygon = new List <SKPoint>();
finalPolygon.Add(points[0]);
(List <SKPoint>, int)poly = polygon1.Contains(points[0]) ? (polygon1, FindIndex(polygon1, points[0])) : (polygon2, FindIndex(polygon2, points[0]));
public static void TestConvexHull()
{
var currentDoc = Application.DocumentManager.MdiActiveDocument;
var editor = currentDoc.Editor;
var database = currentDoc.Database;
// Only select polyline and polyline 2d.
ObjectId polylineId = ObjectId.Null;
while (true)
{
var options = new PromptEntityOptions("\n选择一条曲线：");
var result = editor.GetEntity(options);
if (result.Status == PromptStatus.OK)
{
polylineId = result.ObjectId;
break;
}
if (result.Status == PromptStatus.Cancel)
{
break;
}
editor.WriteMessage("\n选择无效");
}
if (polylineId.IsNull)
{
return;
}
using (var transaction = database.TransactionManager.StartTransaction())
{
IEnumerable <Point3d> points = CurveUtils.GetDistinctVertices(polylineId, transaction);
var convex = new ConvexHull <Point3d>(points, it => it.X, it => it.Y,
(x, y) => new Point3d(x, y, 0), (a, b) => a == b);
convex.CalcConvexHull();
var hullPoints = convex.GetResultsAsArrayOfPoint();
var polyline = new Autodesk.AutoCAD.DatabaseServices.Polyline();
for (int i = 0; i < hullPoints.Length; i++)
{
polyline.AddVertexAt(i, new Point2d(hullPoints[i].X, hullPoints[i].Y), 0, 1, 1);
}
polyline.ColorIndex = 2;
var modelspaceId = SymbolUtilityServices.GetBlockModelSpaceId(database);
var modelspace = transaction.GetObject(modelspaceId, OpenMode.ForWrite) as BlockTableRecord;
modelspace.AppendEntity(polyline);
transaction.AddNewlyCreatedDBObject(polyline, true);
transaction.Commit();
}
}