// This traces sector lines to create a polygon tree
private static List <EarClipPolygon> DoTrace(Sector s)
{
Dictionary <Sidedef, bool> todosides = new Dictionary <Sidedef, bool>(s.Sidedefs.Count);
Dictionary <Vertex, Vertex> ignores = new Dictionary <Vertex, Vertex>();
List <EarClipPolygon> root = new List <EarClipPolygon>();
// Fill the dictionary
// The bool value is used to indicate lines which has been visited in the trace
foreach (Sidedef sd in s.Sidedefs)
{
todosides.Add(sd, false);
}
// First remove all sides that refer to the same sector on both sides of the line
RemoveDoubleSidedefReferences(todosides, s.Sidedefs);
// Continue until all sidedefs have been processed
while (todosides.Count > 0)
{
// Reset all visited indicators
foreach (Sidedef sd in s.Sidedefs)
{
if (todosides.ContainsKey(sd))
{
todosides[sd] = false;
}
}
// Find the right-most vertex to start a trace with.
// This guarantees that we start out with an outer polygon and we just
// have to check if it is inside a previously found polygon.
Vertex start = FindRightMostVertex(todosides, ignores);
// No more possible start vertex found?
// Then leave with what we have up till now.
if (start == null)
{
break;
}
// Trace to find a polygon
SidedefsTracePath path = DoTracePath(new SidedefsTracePath(), start, null, s, todosides);
// If tracing is not possible (sector not closed?)
// then add the start to the ignore list and try again later
if (path == null)
{
// Ignore vertex as start
ignores.Add(start, start);
}
else
{
// Remove the sides found in the path
foreach (Sidedef sd in path)
{
todosides.Remove(sd);
}
// Create the polygon
EarClipPolygon newpoly = path.MakePolygon();
// Determine where this polygon goes in our tree
foreach (EarClipPolygon p in root)
{
// Insert if it belongs as a child
if (p.InsertChild(newpoly))
{
// Done
newpoly = null;
break;
}
}
// Still not inserted in our tree?
if (newpoly != null)
{
// Then add it at root level as outer polygon
newpoly.Inner = false;
root.Add(newpoly);
}
}
}
// Return result
return(root);
}
// Constructor
public SidedefsTracePath(SidedefsTracePath p, Sidedef add) : base(p)
{
// Initialize
base.Add(add);
}
// This recursively traces a path
// Returns the resulting TracePath when the search is complete
// or returns null when no path found.
private static SidedefsTracePath DoTracePath(SidedefsTracePath history, Vertex fromhere, Vertex findme, Sector sector, Dictionary <Sidedef, bool> sides)
{
// Found the vertex we are tracing to?
if (fromhere == findme)
{
return(history);
}
// On the first run, findme is null (otherwise the trace would end
// immeditely when it starts) so set findme here on the first run.
if (findme == null)
{
findme = fromhere;
}
// Make a list of sides referring to the same sector
List <Sidedef> allsides = new List <Sidedef>(fromhere.Linedefs.Count * 2);
foreach (Linedef l in fromhere.Linedefs)
{
// Should we go along the front or back side?
// This is very important for clockwise polygon orientation!
if (l.Start == fromhere)
{
// Front side of line connected to sector?
if ((l.Front != null) && (l.Front.Sector == sector))
{
// Visit here when not visited yet
if (sides.ContainsKey(l.Front) && !sides[l.Front])
{
allsides.Add(l.Front);
}
}
}
else
{
// Back side of line connected to sector?
if ((l.Back != null) && (l.Back.Sector == sector))
{
// Visit here when not visited yet
if (sides.ContainsKey(l.Back) && !sides[l.Back])
{
allsides.Add(l.Back);
}
}
}
}
// Previous line available?
if (history.Count > 0)
{
// This is done to ensure the tracing works along vertices that are shared by
// more than 2 lines/sides of the same sector. We must continue tracing along
// the first next smallest delta angle! This sorts the smallest delta angle to
// the top of the list.
SidedefAngleSorter sorter = new SidedefAngleSorter(history[history.Count - 1], fromhere);
allsides.Sort(sorter);
}
// Go for all lines connected to this vertex
foreach (Sidedef s in allsides)
{
// Mark sidedef as visited and move to next vertex
sides[s] = true;
SidedefsTracePath nextpath = new SidedefsTracePath(history, s);
Vertex nextvertex = (s.Line.Start == fromhere ? s.Line.End : s.Line.Start);
SidedefsTracePath result = DoTracePath(nextpath, nextvertex, findme, sector, sides);
if (result != null)
{
return(result);
}
}
// Nothing found
return(null);
}
