Boprs/Region.cs

#if ACAD24
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Colors;
using AcAp = Autodesk.AutoCAD.ApplicationServices;
#elif BCAD
using Bricscad.EditorInput;
using Teigha.Geometry;
using Teigha.DatabaseServices;
using Teigha.Colors;
#endif
using System;
using System.Collections.Generic;

namespace Boprs
{
	/// <summary>
	/// Geometric region used for boolean operations calculations.
	/// </summary>
	public class Region
	{
		/// <summary>
		/// Edges belonging to this polygon.
		/// </summary>
		private List<SweepEdge> Edges { get; set; }

		private List<Contour> Contours { get; set; }

		/// <summary>
		/// Subdivide my edges, set their inOut tags and validate their non-colinearity.
		/// </summary>
		private void SetEdges(List<SweepVertex> vertices)
		{
			// Lexico-graphically sort my vertices.
			vertices.Sort();

			// Sweepline to keep track of edges.
			SweepLine sweepLine = new SweepLine();

			// Processed edges will be moved here.
			List<SweepEdge> processed = new List<SweepEdge>();

			// Go through all the sorted vertices, test for intersections when appropriate and,
			// if needed, subdivide the edges.
			while (vertices.Count != 0)
			{
				SweepVertex acVx = vertices[0];
				vertices.RemoveAt(0);

				if (acVx.IsLeft())
				{
					sweepLine.Add(acVx.Edge, true);

					SweepEdge prevEdge = sweepLine.PrevEdge(acVx.Edge);
					SweepEdge nextEdge = sweepLine.NextEdge(acVx.Edge);

					acVx.Edge.SetTransitionInside(prevEdge);

					if (prevEdge != null)
					{
						List<SweepVertex> newVertices = acVx.Edge.TrySubdivideBy(prevEdge);

						foreach (SweepVertex vertex in newVertices)
						{
							Utils.InsertVertexSorted(vertices, vertex);
						}
					}
					if (nextEdge != null)
					{
						List<SweepVertex> newVertices = acVx.Edge.TrySubdivideBy(nextEdge);

						foreach (SweepVertex vertex in newVertices)
						{
							Utils.InsertVertexSorted(vertices, vertex);
						}
					}
				}
				else
				{
					SweepEdge prevEdge = sweepLine.PrevEdge(acVx.Edge);
					SweepEdge nextEdge = sweepLine.NextEdge(acVx.Edge);

					sweepLine.Remove(acVx.Edge);
					processed.Add(acVx.Edge);

					if (prevEdge != null && nextEdge != null)
					{
						List<SweepVertex> newVertices = prevEdge.TrySubdivideBy(nextEdge);

						foreach (SweepVertex vertex in newVertices)
						{
							Utils.InsertVertexSorted(vertices, vertex);
						}
					}
				}
			}

			Edges = processed;
		}

		/// <summary>
		/// Find the index of an un-processed vertex with the same position as the one on specified index.
		/// </summary>
		/// <param name="pos">Index of the current vertex.</param>
		/// <param name="vertices">List of vertices.</param>
		/// <param name="processed">Mask for processed vertices.</param>
		/// <returns>Index of an unprocessed neighbour with the same position.</returns>
		private int NextPos(int pos, List<SweepVertex> vertices, bool[] processed)
		{
			int newPos = pos + 1;
			while(newPos < vertices.Count && Utils.DoubleEquals(vertices[pos].Point.GetDistanceTo(vertices[newPos].Point), 0))
			{
				if (!processed[newPos])
				{
					return newPos;
				}
				else
				{
					newPos++;
				}
			}
			newPos = pos - 1;
			while (newPos >= 0 && Utils.DoubleEquals(vertices[pos].Point.GetDistanceTo(vertices[newPos].Point), 0))
			{
				if (!processed[newPos])
				{
					return newPos;
				}
				else
				{
					newPos--;
				}
			}
			throw new Exception("Hit contour dead end (non-connected edge).");
		}

		/// <summary>
		/// Compute my closed contours.
		/// </summary>
		private void ComputeContours()
		{
			// Gather all vertices of the region.
			List<SweepVertex> vertices = new List<SweepVertex>();
			foreach (SweepEdge edge in Edges)
			{
				vertices.Add(edge.LeftVertex);
				vertices.Add(edge.RightVertex);
			}

			// Lexico-graphically sort the vertices.
			vertices.Sort();

			// Sweepline to keep track of edges.
			SweepLine sweepLine = new SweepLine();

			bool[] processed = new bool[vertices.Count]; 
			List<Contour> contours = new List<Contour>();

			for(int i = 0; i < vertices.Count; i++)
			{
				SweepVertex acVx = vertices[i];

				if (acVx.IsLeft())
				{
					sweepLine.Add(acVx.Edge, false);
				}
				else
				{ 
					sweepLine.Remove(acVx.Edge);
				}

				if (processed[i])
				{
					continue;
				}

				Contour contour = new Contour();
				contours.Add(contour);

				SweepEdge prev = sweepLine.PrevEdge(acVx.Edge);
				bool shouldBeCW = prev == null ? false : prev.TransitionInside;

				Point2d target = acVx.Point;

				int pos = i;
				processed[i] = true;
				contour.Vertices.Add(vertices[pos].Point);
				acVx.Edge.ParentContour = contour;
				while (!Utils.DoubleEquals(vertices[pos].OtherVertex().Point.GetDistanceTo(target), 0))
				{
					int otherPos = vertices.IndexOf(vertices[pos].OtherVertex());
					pos = NextPos(otherPos, vertices, processed);

					processed[pos] = true;
					processed[otherPos] = true;

					vertices[pos].Edge.ParentContour = contour;
					contour.Vertices.Add(vertices[pos].Point);
				}
				processed[vertices.IndexOf(vertices[pos].OtherVertex())] = true;
				
				if (shouldBeCW != contour.IsClockwise())
				{
					contour.Reverse();
				}
			}
			Contours = contours;
		}

		/// <summary>
		/// Get a copy of the regions edges list.
		/// </summary>
		/// <returns>Copy of the regions edges list.</returns>
		internal List<SweepEdge> GetEdgeCopies()
		{
			List<SweepEdge> copies = new List<SweepEdge>();

			foreach (SweepEdge edge in Edges)
			{
				copies.Add((SweepEdge)edge.Clone());
			}

			return copies;
		}

		/// <summary>
		/// Get a copy of the contours of the polygon.
		/// </summary>
		/// <returns>List of copies of the regions contours.</returns>
		public List<Contour> GetContourCopies()
		{
			throw new NotImplementedException();
		}

		/// <summary>
		/// Instantiate a region with edges defined by a list of given line segments.
		/// </summary>
		/// <param name="segments"></param>
		/// <returns></returns>
		public static Region FromSegments(List<LineSegment2d> segments)
		{
			Region region = new Region();

			List<SweepVertex> vertices = new List<SweepVertex>();

			foreach(LineSegment2d segment in segments)
			{
				SweepEdge newEdge = new SweepEdge(segment.StartPoint, segment.EndPoint);
				vertices.Add(newEdge.LeftVertex);
				vertices.Add(newEdge.RightVertex);
				newEdge.ParentRegion = region;
			}

			region.SetEdges(vertices);
			region.ComputeContours();

			return region;
		}

#if DEBUG
		internal void Draw()
		{
			foreach (Contour contour in Contours)
			{
				contour.Draw();
			}
		}
#endif
	}
}