//combine segments to paths
//algorithm: make a tiled index with the endpoints of the segments
//for each segment search in the tile and neighboring tiles for matches
//only examine neighboring tiles if the tile is within distMax from current point
public static List <SegmentPath> segments_to_paths__tiles2(List <Segment> segments, float distMax = 1e-10f)
{
List <SegmentPath> paths = new List <SegmentPath>();
//create SegmentTiles
int tileLen = 30; //number of tiles per row/column
Segment[] segs = segments.ToArray();
float xmin = float.MaxValue;
float ymin = float.MaxValue;
float xmax = float.MinValue;
float ymax = float.MinValue;
foreach (Segment s in segs)
{
foreach (Vector2F v in s.p)
{
if (xmin > v.X)
{
xmin = v.X;
}
if (xmax < v.X)
{
xmax = v.X;
}
if (ymin > v.Y)
{
ymin = v.Y;
}
if (ymax < v.Y)
{
ymax = v.Y;
}
}
}
float xstep = (xmax - xmin) / tileLen;
float ystep = (ymax - ymin) / tileLen;
List <SegmentTilePoint>[] segTiles = new List <SegmentTilePoint> [(tileLen + 2) * (tileLen + 2)]; //add extra row/column around perimeter
for (int i = 0; i < (tileLen + 2) * (tileLen + 2); i++)
{
segTiles[i] = new List <SegmentTilePoint>();
}
SegmentTilePoint[] sidx = new SegmentTilePoint[2];
for (int seg_i = 0; seg_i < segs.Length; seg_i++)
{
Segment s = segs[seg_i];
for (int j = 0; j < 2; j++)
{
int idx_x = (int)((s.p[j].X - xmin) / xstep);
int idx_y = (int)((s.p[j].Y - ymin) / ystep);
int idx = (idx_y + 1) * tileLen + (idx_x + 1);
sidx[j] = new SegmentTilePoint(seg_i, s.p[j], null);
segTiles[idx].Add(sidx[j]);
}
sidx[0].othersegidx = sidx[1];
sidx[1].othersegidx = sidx[0];
}
//array near defines the tile offsets to: current tile, left-above, above, right-above, left, right, left-below, below, right-below
int[] near = new int[] { 0, -tileLen - 1, -tileLen, -tileLen + 1, -1, 1, tileLen - 1, tileLen, tileLen + 1 };
//process each segment
for (int seg_i = 0; seg_i < segs.Length; seg_i++)
{
Segment seg = segs[seg_i];
if (seg == null)
{
continue;
}
segs[seg_i] = null;
SegmentPath path = new SegmentPath(seg.p);
paths.Add(path);
//find poins that match the end of the path
bool pointadded;
do
{
pointadded = false;
Vector2F pathendpoint = path.p.Last.Value;
int idx_x = (int)((pathendpoint.X - xmin) / xstep);
int idx_y = (int)((pathendpoint.Y - ymin) / ystep);
int idx = (idx_y + 1) * tileLen + (idx_x + 1);
float x0 = xmin + idx_x * xstep;
float x1 = xmin + (idx_x + 1) * xstep;
float y0 = ymin + idx_y * ystep;
float y1 = xmin + (idx_y + 1) * ystep;
for (int near_i = 0; !pointadded && near_i < 9; near_i++)
{
//check if need to examine tile for possible matches
switch (near_i)
{
case 0: break;
case 1: if (pathendpoint.X - distMax > x0 && pathendpoint.Y - distMax > y0)
{
continue;
}
break; //left-above
case 2: if (pathendpoint.Y - distMax > y0)
{
continue;
}
break; //above
case 3: if (pathendpoint.X + distMax < x1 && pathendpoint.Y - distMax > y0)
{
continue;
}
break; //right-above
case 4: if (pathendpoint.X - distMax > x0)
{
continue;
}
break; //left
case 5: if (pathendpoint.X + distMax < x1)
{
continue;
}
break; //right
case 6: if (pathendpoint.X - distMax > x0 && pathendpoint.Y + distMax < y1)
{
continue;
}
break; //left-below
case 7: if (pathendpoint.Y + distMax < y1)
{
continue;
}
break; //below
case 8: if (pathendpoint.X + distMax < x1 && pathendpoint.Y + distMax < y1)
{
continue;
}
break; //right-below
}
List <SegmentTilePoint> sgidx = segTiles[idx + near[near_i]];
foreach (SegmentTilePoint si in sgidx)
{
if (si.alive && Vector2F.DistanceManhattan(pathendpoint, si.p) < distMax)
{
path.p.AddLast(si.othersegidx.p);
si.alive = false;
si.othersegidx.alive = false;
segs[si.seg_i] = null;
pointadded = true;
break;
}
}
}
} while (pointadded);
//find poins that match the beginning of the path
do
{
pointadded = false;
Vector2F pathbeginpoint = path.p.First.Value;
int idx_x = (int)((pathbeginpoint.X - xmin) / xstep);
int idx_y = (int)((pathbeginpoint.Y - ymin) / ystep);
int idx = (idx_y + 1) * tileLen + (idx_x + 1);
float x0 = xmin + idx_x * xstep;
float x1 = xmin + (idx_x + 1) * xstep;
float y0 = ymin + idx_y * ystep;
float y1 = xmin + (idx_y + 1) * ystep;
for (int near_i = 0; !pointadded && near_i < 9; near_i++)
{
//check if need to examine tile for possible matches
switch (near_i)
{
case 0: break;
case 1: if (pathbeginpoint.X - distMax > x0 && pathbeginpoint.Y - distMax > y0)
{
continue;
}
break; //left-above
case 2: if (pathbeginpoint.Y - distMax > y0)
{
continue;
}
break; //above
case 3: if (pathbeginpoint.X + distMax < x1 && pathbeginpoint.Y - distMax > y0)
{
continue;
}
break; //right-above
case 4: if (pathbeginpoint.X - distMax > x0)
{
continue;
}
break; //left
case 5: if (pathbeginpoint.X + distMax < x1)
{
continue;
}
break; //right
case 6: if (pathbeginpoint.X - distMax > x0 && pathbeginpoint.Y + distMax < y1)
{
continue;
}
break; //left-below
case 7: if (pathbeginpoint.Y + distMax < y1)
{
continue;
}
break; //below
case 8: if (pathbeginpoint.X + distMax < x1 && pathbeginpoint.Y + distMax < y1)
{
continue;
}
break; //right-below
}
List <SegmentTilePoint> sgidx = segTiles[idx + near[near_i]];
foreach (SegmentTilePoint si in sgidx)
{
if (si.alive && Vector2F.DistanceManhattan(pathbeginpoint, si.p) < distMax)
{
path.p.AddFirst(si.othersegidx.p);
si.alive = false;
si.othersegidx.alive = false;
segs[si.seg_i] = null;
pointadded = true;
break;
}
}
}
} while (pointadded);
}
return(paths);
}
public SegmentTilePoint(int seg_i, Vector2F p, SegmentTilePoint othersegidx)
{
this.seg_i = seg_i;
this.p = p;
this.othersegidx = othersegidx;
}
