private static void FillLeftAboveEdgeEvent(DTSweepContext tcx, DTSweepConstraint edge, AdvancingFrontNode node)
{
while (node.Prev.Point.X > edge.P.X)
{
// Check if next node is below the edge
var o1 = TriangulationUtil.Orient2d(edge.Q, node.Prev.Point, edge.P);
if (o1 == Orientation.CW)
{
FillLeftBelowEdgeEvent(tcx, edge, node);
}
else
{
node = node.Prev;
}
}
}
private static void FillLeftBelowEdgeEvent(DTSweepContext tcx, DTSweepConstraint edge, AdvancingFrontNode node)
{
if (node.Point.X > edge.P.X)
{
if (TriangulationUtil.Orient2d(node.Point, node.Prev.Point, node.Prev.Prev.Point) == Orientation.CW)
{
// Concave
FillLeftConcaveEdgeEvent(tcx, edge, node);
}
else
{
// Convex
FillLeftConvexEdgeEvent(tcx, edge, node);
// Retry this one
FillLeftBelowEdgeEvent(tcx, edge, node);
}
}
}
private static void FillEdgeEvent(DTSweepContext tcx, DTSweepConstraint edge, AdvancingFrontNode node)
{
if (tcx.EdgeEvent.Right)
{
FillRightAboveEdgeEvent(tcx, edge, node);
}
else
{
FillLeftAboveEdgeEvent(tcx, edge, node);
}
}
private static void FillLeftConvexEdgeEvent(DTSweepContext tcx, DTSweepConstraint edge, AdvancingFrontNode node)
{
// Next concave or convex?
if (TriangulationUtil.Orient2d(node.Prev.Point, node.Prev.Prev.Point, node.Prev.Prev.Prev.Point) ==
Orientation.CW)
{
// Concave
FillLeftConcaveEdgeEvent(tcx, edge, node.Prev);
}
else
{
// Convex
// Next above or below edge?
if (TriangulationUtil.Orient2d(edge.Q, node.Prev.Prev.Point, edge.P) == Orientation.CW)
{
// Below
FillLeftConvexEdgeEvent(tcx, edge, node.Prev);
}
else
{
// Above
}
}
}
/// <summary>
/// We will traverse the entire advancing front and fill it to form a convex hull.
/// </summary>
private static void TurnAdvancingFrontConvex(DTSweepContext tcx, AdvancingFrontNode b, AdvancingFrontNode c)
{
var first = b;
while (c != tcx.aFront.Tail)
{
if (TriangulationUtil.Orient2d(b.Point, c.Point, c.Next.Point) == Orientation.CCW)
{
// [b,c,d] Concave - fill around c
Fill(tcx, c);
c = c.Next;
}
else
{
// [b,c,d] Convex
if (b != first && TriangulationUtil.Orient2d(b.Prev.Point, b.Point, c.Point) == Orientation.CCW)
{
// [a,b,c] Concave - fill around b
Fill(tcx, b);
b = b.Prev;
}
else
{
// [a,b,c] Convex - nothing to fill
b = c;
c = c.Next;
}
}
}
}
