// Set the initial ActiveLowSide and ActiveHighSide of the obstacle starting at this point.
internal void CreateInitialSides(PolylinePoint startPoint, ScanDirection scanDir)
{
Debug.Assert((null == ActiveLowSide) && (null == ActiveHighSide)
, "Cannot call SetInitialSides when sides are already set");
ActiveLowSide = new LowObstacleSide(this, startPoint, scanDir);
ActiveHighSide = new HighObstacleSide(this, startPoint, scanDir);
if (scanDir.IsFlat(ActiveHighSide))
{
// No flat sides in the scanline; we'll do lookahead processing in the scanline to handle overlaps
// with existing segments, and normal neighbor handling will take care of collinear OpenVertexEvents.
ActiveHighSide = new HighObstacleSide(this, ActiveHighSide.EndVertex, scanDir);
}
}
} // end ProcessEvent(OpenVertexEvent)
void ProcessEvent(LowBendVertexEvent lowVertEvent) {
// Note: we only draw lines only from "interesting" vertices, which would be those
// that open or close an obstacle, as well as staircase Reflections (see doc). This means
// Low/HighVertexEvents routines will just track the change in ActiveLowSide/ActiveHighSide.
// This is a vertex on the low side of the obstacle. Update the ActiveLowSide in the obstacle
// and scanline (this also checks for Reflection events).
var obstacle = lowVertEvent.Obstacle;
var lowSide = new LowObstacleSide(obstacle, lowVertEvent.Vertex, ScanDirection);
// If the new lowSide is flat we don't remove it due to potential overlaps; that lets any collinear
// OpenVertexEvents know they are overlapped (touching == overlap). When we get to CloseVertexEvent,
// keeping the current ActiveLowSide in the scanline tells us how when the interior sides stop
// so we know when we've found a neighbor. Similarly, if we're turning down toward the
// scanline, we let CloseVertexEvent remove the side (in case there are coincident vertices).
// That leaves the case of still ascending, where we replace the side in the scanline.
if (ScanDirection.ComparePerpCoord(lowSide.End, lowSide.Start) > 0) {
this.RemoveSideFromScanLine(this.scanLine.Find(obstacle.ActiveLowSide), lowVertEvent.Site);
AddSideToScanLine(lowSide, lowVertEvent.Site);
obstacle.ActiveLowSide = lowSide;
EnqueueLowBendVertexEvent(lowSide);
}
} // end ProcessEvent(LowBendVertexEvent)
internal LowReflectionEvent(BasicReflectionEvent previousSite, LowObstacleSide targetSide, Point site)
: base(previousSite, targetSide.Obstacle, site)
{
this.Side = targetSide;
}
internal LowReflectionEvent(BasicReflectionEvent previousSite, LowObstacleSide targetSide, Point site)
: base (previousSite, targetSide.Obstacle, site) {
this.Side = targetSide;
}
// As described in the document, we currently don't create ScanSegments where a flat top/bottom boundary may have
// intervals that are embedded within overlapped segments:
// obstacle1 | |obstacle2 | obstacle3 | | obstacle4 | obstacle2| |
// | +-----------|===========|??????????|===========|----------+ | obstacle5
// ...__________| |___________| |___________| |__________...
// Here, there will be no ScanSegment created at ??? along the border of obstacle2 between obstacle3
// and obstacle4. This is not a concern because that segment is useless anyway; a path from outside
// obstacle2 will not be able to see it unless there is another obstacle in that gap, and then that
// obstacle's side-derived ScanSegments will create non-overlapped edges; and there are already edges
// from the upper/lower extreme vertices of obstacle 3 and obstacle4 to ensure a connected graph.
// If there is a routing from an obstacle outside obstacle2 to one embedded within obstacle2, the
// port visibility will create the necessary edges.
//
// We don't try to determine nesting depth and create different VisibilityEdge weights to prevent spurious
// nested-obstacle crossings; we just care about overlapped vs. not-overlapped.
// If this changes, we would have to: Find the overlap depth at the lowNborSide intersection,
// then increment/decrement according to side type as we move from low to high, then create a different
// ScanSegment at each obstacle-side crossing, making ScanSegment.IsOverlapped a depth instead of bool.
// Then pass that depth through to VisibilityEdge as an increased weight. (This would also automatically
// handle the foregoing situation of non-overlapped intervals in the middle of a flat top/bottom border,
// not that it would really gain anything).
void CreateScanSegments(Obstacle obstacle, HighObstacleSide lowNborSide, BasicObstacleSide lowOverlapSide,
BasicObstacleSide highOverlapSide, LowObstacleSide highNborSide, BasicVertexEvent vertexEvent) {
// If we have either of the high/low OverlapSides, we'll need to see if they're inside
// another obstacle. If not, they end the overlap.
if ((null == highOverlapSide) || IntersectionAtSideIsInsideAnotherObstacle(highOverlapSide, vertexEvent)) {
highOverlapSide = highNborSide;
}
if ((null == lowOverlapSide) || IntersectionAtSideIsInsideAnotherObstacle(lowOverlapSide, vertexEvent)) {
lowOverlapSide = lowNborSide;
}
// There may be up to 3 segments; for a simple diagram, |# means low-side border of
// obstacle '#' and #| means high-side, with 'v' meaning our event vertex. Here are
// the two cases where we create a single non-overlapped ScanSegment (from the Low
// side in the diagram, but the same logic works for the High side).
// - non-overlapped: 1| v |2
// ...---+ +---...
// - non-overlapped to an "inner" highNbor on a flat border: 1| vLow |2 vHigh
// ...---+ +-----+=========...
// This may be the low side of a flat bottom or top border, so lowNbor or highNbor
// may be in the middle of the border.
Point lowNborIntersect = ScanLineIntersectSide(vertexEvent.Site, lowNborSide);
Point highNborIntersect = ScanLineIntersectSide(vertexEvent.Site, highNborSide);
bool lowNborEndpointIsOverlapped = IntersectionAtSideIsInsideAnotherObstacle(lowNborSide,
vertexEvent.Obstacle /*obstacleToIgnore*/, lowNborIntersect);
if (!lowNborEndpointIsOverlapped && (lowNborSide == lowOverlapSide)) {
// Nothing is overlapped so create one segment.
AddSegment(lowNborIntersect, highNborIntersect, obstacle, lowNborSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
return;
}
// Here are the different interval combinations for overlapped cases.
// - non-overlapped, overlapped: 1| |2 v |3
// ...---+ +------+===...
// - non-overlapped, overlapped, non-overlapped: 1| |2 v 2| |3
// ==+ +-------+ +--...
// - overlapped: |1 2| v |3 ...1|
// ...---+====+-----+===...-+
// - overlapped, non-overlapped: |1 2| v 1| |3
// ...---+====+------+ +---...
// We will not start overlapped and then go to non-overlapped and back to overlapped,
// because we would have found the overlap-ending/beginning sides as nearer neighbors.
// Get the other intersections we'll want.
Point highOverlapIntersect = (highOverlapSide == highNborSide) ? highNborIntersect
: ScanLineIntersectSide(vertexEvent.Site, highOverlapSide);
Point lowOverlapIntersect = (lowOverlapSide == lowNborSide) ? lowNborIntersect
: ScanLineIntersectSide(vertexEvent.Site, lowOverlapSide);
// Create the segments.
if (!lowNborEndpointIsOverlapped) {
// First interval is non-overlapped; there is a second overlapped interval, and may be a
// third non-overlapping interval if another obstacle surrounded this vertex.
AddSegment(lowNborIntersect, lowOverlapIntersect, obstacle, lowNborSide, lowOverlapSide, vertexEvent,
ScanSegment.NormalWeight);
AddSegment(lowOverlapIntersect, highOverlapIntersect, obstacle, lowOverlapSide, highOverlapSide, vertexEvent,
ScanSegment.OverlappedWeight);
if (highOverlapSide != highNborSide) {
AddSegment(highOverlapIntersect, highNborIntersect, obstacle, highOverlapSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
}
}
else {
// Starts off overlapped so ignore lowOverlapSide.
AddSegment(lowNborIntersect, highOverlapIntersect, obstacle, lowNborSide, highOverlapSide, vertexEvent,
ScanSegment.OverlappedWeight);
if (highOverlapSide != highNborSide) {
AddSegment(highOverlapIntersect, highNborIntersect, obstacle, highOverlapSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
}
}
}
// As described in the document, we currently don't create ScanSegments where a flat top/bottom boundary may have
// intervals that are embedded within overlapped segments:
// obstacle1 | |obstacle2 | obstacle3 | | obstacle4 | obstacle2| |
// | +-----------|===========|??????????|===========|----------+ | obstacle5
// ...__________| |___________| |___________| |__________...
// Here, there will be no ScanSegment created at ??? along the border of obstacle2 between obstacle3
// and obstacle4. This is not a concern because that segment is useless anyway; a path from outside
// obstacle2 will not be able to see it unless there is another obstacle in that gap, and then that
// obstacle's side-derived ScanSegments will create non-overlapped edges; and there are already edges
// from the upper/lower extreme vertices of obstacle 3 and obstacle4 to ensure a connected graph.
// If there is a routing from an obstacle outside obstacle2 to one embedded within obstacle2, the
// port visibility will create the necessary edges.
//
// We don't try to determine nesting depth and create different VisibilityEdge weights to prevent spurious
// nested-obstacle crossings; we just care about overlapped vs. not-overlapped.
// If this changes, we would have to: Find the overlap depth at the lowNborSide intersection,
// then increment/decrement according to side type as we move from low to high, then create a different
// ScanSegment at each obstacle-side crossing, making ScanSegment.IsOverlapped a depth instead of bool.
// Then pass that depth through to VisibilityEdge as an increased weight. (This would also automatically
// handle the foregoing situation of non-overlapped intervals in the middle of a flat top/bottom border,
// not that it would really gain anything).
void CreateScanSegments(Obstacle obstacle, HighObstacleSide lowNborSide, BasicObstacleSide lowOverlapSide,
BasicObstacleSide highOverlapSide, LowObstacleSide highNborSide, BasicVertexEvent vertexEvent)
{
// If we have either of the high/low OverlapSides, we'll need to see if they're inside
// another obstacle. If not, they end the overlap.
if ((null == highOverlapSide) || IntersectionAtSideIsInsideAnotherObstacle(highOverlapSide, vertexEvent))
{
highOverlapSide = highNborSide;
}
if ((null == lowOverlapSide) || IntersectionAtSideIsInsideAnotherObstacle(lowOverlapSide, vertexEvent))
{
lowOverlapSide = lowNborSide;
}
// There may be up to 3 segments; for a simple diagram, |# means low-side border of
// obstacle '#' and #| means high-side, with 'v' meaning our event vertex. Here are
// the two cases where we create a single non-overlapped ScanSegment (from the Low
// side in the diagram, but the same logic works for the High side).
// - non-overlapped: 1| v |2
// ...---+ +---...
// - non-overlapped to an "inner" highNbor on a flat border: 1| vLow |2 vHigh
// ...---+ +-----+=========...
// This may be the low side of a flat bottom or top border, so lowNbor or highNbor
// may be in the middle of the border.
Point lowNborIntersect = ScanLineIntersectSide(vertexEvent.Site, lowNborSide);
Point highNborIntersect = ScanLineIntersectSide(vertexEvent.Site, highNborSide);
bool lowNborEndpointIsOverlapped = IntersectionAtSideIsInsideAnotherObstacle(lowNborSide,
vertexEvent.Obstacle /*obstacleToIgnore*/, lowNborIntersect);
if (!lowNborEndpointIsOverlapped && (lowNborSide == lowOverlapSide))
{
// Nothing is overlapped so create one segment.
AddSegment(lowNborIntersect, highNborIntersect, obstacle, lowNborSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
return;
}
// Here are the different interval combinations for overlapped cases.
// - non-overlapped, overlapped: 1| |2 v |3
// ...---+ +------+===...
// - non-overlapped, overlapped, non-overlapped: 1| |2 v 2| |3
// ==+ +-------+ +--...
// - overlapped: |1 2| v |3 ...1|
// ...---+====+-----+===...-+
// - overlapped, non-overlapped: |1 2| v 1| |3
// ...---+====+------+ +---...
// We will not start overlapped and then go to non-overlapped and back to overlapped,
// because we would have found the overlap-ending/beginning sides as nearer neighbors.
// Get the other intersections we'll want.
Point highOverlapIntersect = (highOverlapSide == highNborSide) ? highNborIntersect
: ScanLineIntersectSide(vertexEvent.Site, highOverlapSide);
Point lowOverlapIntersect = (lowOverlapSide == lowNborSide) ? lowNborIntersect
: ScanLineIntersectSide(vertexEvent.Site, lowOverlapSide);
// Create the segments.
if (!lowNborEndpointIsOverlapped)
{
// First interval is non-overlapped; there is a second overlapped interval, and may be a
// third non-overlapping interval if another obstacle surrounded this vertex.
AddSegment(lowNborIntersect, lowOverlapIntersect, obstacle, lowNborSide, lowOverlapSide, vertexEvent,
ScanSegment.NormalWeight);
AddSegment(lowOverlapIntersect, highOverlapIntersect, obstacle, lowOverlapSide, highOverlapSide, vertexEvent,
ScanSegment.OverlappedWeight);
if (highOverlapSide != highNborSide)
{
AddSegment(highOverlapIntersect, highNborIntersect, obstacle, highOverlapSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
}
}
else
{
// Starts off overlapped so ignore lowOverlapSide.
AddSegment(lowNborIntersect, highOverlapIntersect, obstacle, lowNborSide, highOverlapSide, vertexEvent,
ScanSegment.OverlappedWeight);
if (highOverlapSide != highNborSide)
{
AddSegment(highOverlapIntersect, highNborIntersect, obstacle, highOverlapSide, highNborSide, vertexEvent,
ScanSegment.NormalWeight);
}
}
}
// Set the initial ActiveLowSide and ActiveHighSide of the obstacle starting at this point.
internal void CreateInitialSides(PolylinePoint startPoint, ScanDirection scanDir) {
Debug.Assert((null == ActiveLowSide) && (null == ActiveHighSide)
, "Cannot call SetInitialSides when sides are already set");
ActiveLowSide = new LowObstacleSide(this, startPoint, scanDir);
ActiveHighSide = new HighObstacleSide(this, startPoint, scanDir);
if (scanDir.IsFlat(ActiveHighSide)) {
// No flat sides in the scanline; we'll do lookahead processing in the scanline to handle overlaps
// with existing segments, and normal neighbor handling will take care of collinear OpenVertexEvents.
ActiveHighSide = new HighObstacleSide(this, ActiveHighSide.EndVertex, scanDir);
}
}