Boprs/SweepEdge.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;
using AcAp = Bricscad.ApplicationServices;
#endif
using System;
using System.Collections.Generic;

namespace Boprs
{
	/// <summary>
	/// Type the edge can be.
	/// </summary>
	internal enum EdgeType
	{
		/// <summary>
		/// Normal edge, nothing special.
		/// </summary>
		NORMAL,
		/// <summary>
		/// Edge overlaps with an edge on another region, 
		/// both represent the same transition (in or out) of their respective regions.
		/// </summary>
		OVERLAP_SAME,
		/// <summary>
		/// Edge overlaps with an edge on another region, 
		/// both represent a different transition (in or out) of their respective regions.
		/// </summary>
		OVERLAP_DIFFERENT,
		/// <summary>
		/// Edge overlaps with an edge on another region, it will handle the situation.
		/// </summary>
		OVERLAP_SILENT,
	}

	/// <summary>
	/// Line segment (edge) used while a sweep line is processing a boolean operation.
	/// </summary>
	internal class SweepEdge : ICloneable
	{
		/// <summary>
		/// String representation of the edge.
		/// </summary>
		public override string ToString()
		{
			return ($"({LeftVertex} -- {RightVertex})");
		}

		public object Clone()
		{
			SweepVertex left = (SweepVertex)LeftVertex.Clone();
			SweepVertex right = (SweepVertex)RightVertex.Clone();
			SweepEdge clone = new SweepEdge(LeftVertex, RightVertex)
			{
				TransitionInside = TransitionInside,
				InsideOther = InsideOther,
				Type = Type,
				ParentRegion = ParentRegion,
			};
			return clone;
		}

		/// <summary>
		/// Comparison of edges.
		/// </summary>
		/// <param name="other">Other edge to compare.</param>
		/// <param name="xParam">X param at which to make the comparison.</param>
		/// <returns><c>-1</c> if this is below obj, <c>1</c> if this is above obj, <c>0</c> if collinear.</returns>
		public int CompareTo(SweepEdge other, double xParam)
		{
			// Get the Y values of the edges at the given X coordinate
			// If the edge is vertical, the Y value of its left (lower) endpoint is its Y value for this comparison.
			double myY = IsVertical() ? LeftVertex.Point.Y :
				Utils.YatX(LeftVertex.Point, RightVertex.Point, xParam);

			double otherY = other.IsVertical() ? other.LeftVertex.Point.Y :
				Utils.YatX(other.LeftVertex.Point, other.RightVertex.Point, xParam);

			// If the edges are not intersecting at this X, order them as expected.
			if (!Utils.DoubleEquals(myY, otherY))
			{
				return myY > otherY ? 1 : -1;
			}
			// If the edges do intersect here, and one is vertical, the non-vertical one is "lower".
			if (IsVertical() != other.IsVertical())
			{
				return IsVertical() ? 1 : -1;
			}
			// If they are not collinear, the one leading downwards from here is "lower".
			if (Utils.SignedArea(LeftVertex.Point, RightVertex.Point, other.RightVertex.Point) < 0)
			{
				return 1;
			}
			if (Utils.SignedArea(LeftVertex.Point, RightVertex.Point, other.RightVertex.Point) > 0)
			{
				return -1;
			}
			// If they are collinear, return 0;
			return 0;
		}

		/// <summary>
		/// Left (or bottom) vertex of the edge.
		/// </summary>
		internal SweepVertex LeftVertex { get; set; }

		/// <summary>
		/// Right (or top) vertex of the edge.
		/// </summary>
		internal SweepVertex RightVertex { get; set; }

		/// <summary>
		/// Does this edge signify a transition from the outside to the inside of its region?
		/// </summary>
		internal bool TransitionInside { get; private set; }

		/// <summary>
		/// Is this edge inside the other polygon?
		/// </summary>
		internal bool InsideOther {  get; private set; }

		/// <summary>
		/// Type of the edge.
		/// </summary>
		internal EdgeType Type { get; private set; }

		/// <summary>
		/// Region I belong to.
		/// </summary>
		internal Region ParentRegion { get; set; }

		/// <summary>
		/// Is this edge vertical?
		/// </summary>
		/// <returns><c>true</c> if this vedge is vertical, <c>false</c> if not.</returns>
		internal bool IsVertical()
		{
			return Utils.DoubleEquals(LeftVertex.Point.X, RightVertex.Point.X);
		}

		/// <summary>
		/// Set the TransitionInside flag for this edge.
		/// </summary>
		/// <param name="prevEdge">Edge preceeding this one in the region construction sweep line.</param>
		internal void SetTransitionInside(SweepEdge prevEdge)
		{
			if(prevEdge == null)
			{
				TransitionInside = true;
			}
			else if(IsVertical())
			{
				TransitionInside = prevEdge.TransitionInside;
			}
			else
			{
				TransitionInside = !prevEdge.TransitionInside;
			}
		}

		/// <summary>
		/// Set the InsideOther flag for this edge.
		/// </summary>
		/// <param name="prevEdge">Edge preceeding this one in the bopr processing sweep line.</param>
		internal void SetInsideOther(SweepEdge prevEdge)
		{
			if (prevEdge == null)
			{
				InsideOther = false;
			}
			else if (ParentRegion == prevEdge.ParentRegion)
			{
				InsideOther = prevEdge.InsideOther;
			}
			else
			{
				InsideOther = prevEdge.TransitionInside;
			}
		}

		/// <summary>
		/// Create new edge going from pt to my right vertex and make pt my new right vertex.
		/// </summary>
		/// <param name="pt">Point at which to subdivide.</param>
		/// <returns>List of the two newly created vertices.</returns>
		internal List<SweepVertex> SubdivideAt(Point2d pt)
		{
			// Create the new vertices.
			SweepVertex newLeft = new SweepVertex(pt);
			SweepVertex newRight = new SweepVertex(pt);

			// Create new edge from the point to my right vertex and assign it as the edge of its vertices.
			SweepEdge newEdge = new SweepEdge(newLeft, RightVertex);
			newEdge.TransitionInside = TransitionInside;
			newEdge.ParentRegion = ParentRegion;
			newLeft.Edge = newEdge;
			RightVertex.Edge = newEdge;

			// Set the point as my new right vertex and me as its edge.
			RightVertex = newRight;
			newRight.Edge = this;

			// Return the newly created vertices.
			return new List<SweepVertex>() { newLeft, newRight };
		}

		/// <summary>
		/// Intersect this edge with the other, if there is an intersection, subdivide them.
		/// </summary>
		/// <param name="otherEdge">Edge to try intersecting with.</param>
		/// <returns>Unsorted list of newly created verticies.</returns>
		internal List<SweepVertex> TrySubdivideBy(SweepEdge otherEdge)
		{
			// Get the linesegment representation of this and the other edge.
			LineSegment2d myLine = new LineSegment2d(LeftVertex.Point, RightVertex.Point);
			LineSegment2d otherLine = new LineSegment2d(otherEdge.LeftVertex.Point, otherEdge.RightVertex.Point);

			// Get the potential intersection between the two edges.
			CurveCurveIntersector2d intersector = new CurveCurveIntersector2d(myLine, otherLine);

			// If the intersection was on the endpoints of both segments, return empty list.
			// Right vertices get processed before left ones, so connected left and right vertices
			// will not communicate.
			if (intersector.NumberOfIntersectionPoints == 1)
			{
				List<SweepVertex> newVertices = new List<SweepVertex>();
				Point2d intPt = intersector.GetIntersectionPoint(0);

				// If the point is inside of either edge (not on its end point), subdivide the edge.
				if (!(Utils.DoubleEquals(intPt.GetDistanceTo(LeftVertex.Point), 0) ||
					Utils.DoubleEquals(intPt.GetDistanceTo(RightVertex.Point), 0)))
				{
					newVertices.AddRange(SubdivideAt(intPt));
				}
				if (!(Utils.DoubleEquals(intPt.GetDistanceTo(otherEdge.LeftVertex.Point), 0) ||
					Utils.DoubleEquals(intPt.GetDistanceTo(otherEdge.RightVertex.Point), 0)))
				{
					newVertices.AddRange(otherEdge.SubdivideAt(intPt));
				}

				// Return the newly created vertices.
				return newVertices;
			}

			// Overlap
			if (myLine.Overlaps(otherLine))
			{
				List<SweepVertex> newVertices = new List<SweepVertex>();
				
				// The edges share the left vertex
				if (Utils.DoubleEquals(LeftVertex.Point.GetDistanceTo(otherEdge.LeftVertex.Point), 0))
				{
					EdgeType et = (TransitionInside == otherEdge.TransitionInside) ?
						EdgeType.OVERLAP_SAME : EdgeType.OVERLAP_DIFFERENT;

					// The edges share the right vertex as well, set the edge type for both this and the other
					// edge and return an empty list.
					if (Utils.DoubleEquals(RightVertex.Point.GetDistanceTo(otherEdge.RightVertex.Point), 0))
					{
						Type = et;
						otherEdge.Type = EdgeType.OVERLAP_SILENT;

						return newVertices;
					}
					// One of the edges carries on farther, clip it to be fully overlapping,
					// set the edge type for this and other edge and create a new edge from the clipped off part.
					else
					{
						SweepEdge longer = RightVertex.CompareTo(otherEdge.RightVertex) > 0 ? this : otherEdge;
						SweepEdge shorter = (this == longer) ? otherEdge : this;
						
						newVertices.AddRange(longer.SubdivideAt(shorter.RightVertex.Point));

						Type = et;
						otherEdge.Type = EdgeType.OVERLAP_SILENT;

						return newVertices;
					}
				}
				// One edge starts earlier than the other. Find it and create new edge from the point it
				// intersects the other edge, those two will negtiate how to handle the situation later.
				else
				{
					SweepEdge earlier = LeftVertex.CompareTo(otherEdge.LeftVertex) < 0 ? this : otherEdge;
					SweepEdge later = (this == earlier) ? otherEdge : this;

					newVertices.AddRange(earlier.SubdivideAt(later.LeftVertex.Point));

					return newVertices;
				}
			}

			// If there was no intersection, return empty list
			return new List<SweepVertex>();
		}

		/// <summary>
		/// Constructor.
		/// </summary>
		/// <param name="pt1">Endpoint 1.</param>
		/// <param name="pt2">EndPoint 2.</param>
		internal SweepEdge(Point2d pt1, Point2d pt2)
		{
			if (Utils.DoubleEquals(pt1.GetDistanceTo(pt2), 0))
			{
				throw new ArgumentException("Edge end points cannot be the same.");
			}

			SweepVertex v1 = new SweepVertex(pt1);
			SweepVertex v2 = new SweepVertex(pt2);

			v1.Edge = this;
			v2.Edge = this;
			Type = EdgeType.NORMAL;

			if (v1.CompareTo(v2) < 0)
			{
				LeftVertex = v1;
				RightVertex = v2;
			}
			else
			{
				LeftVertex = v2;
				RightVertex = v1;
			}
		}

		internal SweepEdge(SweepVertex v1, SweepVertex v2)
		{
			Type = EdgeType.NORMAL;

			if (v1.CompareTo(v2) < 0)
			{
				LeftVertex = v1;
				RightVertex = v2;
			}
			else
			{
				LeftVertex = v2;
				RightVertex = v1;
			}
		}

#if DEBUG
		internal ObjectId ObjectId { get; private set; }

		internal void Draw(Color color = null)
		{
			AcAp.Document acDoc = AcAp.Application.DocumentManager.MdiActiveDocument;
			Database acDb = acDoc.Database;

			Erase();

			Color lineColor = color;

			if (color == null)
			{
				if (Type == EdgeType.NORMAL)
				{
					lineColor = TransitionInside ?
						Color.FromRgb(32, 255, 32) : Color.FromRgb(255, 32, 32);
				}
				else
				{
					lineColor = Type == EdgeType.OVERLAP_SAME ? 
						Color.FromRgb(32, 32, 255) : Color.FromRgb(255, 255, 32);
				}
			}

			using (Transaction acTrans = acDb.TransactionManager.StartTransaction())
			{
				// Open the BlockTableRecord
				BlockTable acBlkTbl = (BlockTable)acTrans.GetObject(acDb.BlockTableId, OpenMode.ForRead);
				BlockTableRecord acBlkTblRec =
					(BlockTableRecord)acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace], OpenMode.ForWrite);

				Line asLine = new Line(LeftVertex.Point.To3d(), RightVertex.Point.To3d());
				asLine.Color = lineColor;
				acBlkTblRec.AppendEntity(asLine);
				acTrans.AddNewlyCreatedDBObject(asLine, true);

				acTrans.Commit();

				ObjectId = asLine.ObjectId;
			}
		}

		internal void Erase()
		{
			AcAp.Document acDoc = AcAp.Application.DocumentManager.MdiActiveDocument;
			Database acDb = acDoc.Database;

			if (!ObjectId.IsNull && !ObjectId.IsEffectivelyErased)
			{
				using (Transaction acTrans = acDb.TransactionManager.StartTransaction())
				{
					acTrans.GetObject(ObjectId, OpenMode.ForWrite).Erase();
					acTrans.Commit();
				}
			}
		}
#endif
	}
}