/// <summary>
/// Visits all crossings of the current edge with all edges of the given index
/// cell of B. Terminates early and returns false if visitor_ returns false.
/// </summary>
private bool VisitEdgeCellCrossings(ShapeEdge a, S2ShapeIndexCell b_cell)
{
// Test the current edge of A against all edges of "b_cell".
// Note that we need to use a new S2EdgeCrosser (or call Init) whenever we
// replace the contents of b_shape_edges_, since S2EdgeCrosser requires that
// its S2Point arguments point to values that persist between Init() calls.
GetShapeEdges(b_index_, b_cell, b_shape_edges_);
var crosser = new S2EdgeCrosser(a.V0, a.V1);
foreach (var b in b_shape_edges_)
{
if (crosser.C == S2Point.Empty || crosser.C != b.V0)
{
crosser.RestartAt(b.V0);
}
int sign = crosser.CrossingSign(b.V1);
if (sign >= min_crossing_sign_)
{
if (!VisitEdgePair(a, b, sign == 1))
{
return(false);
}
}
}
return(true);
}
/// <summary>
/// Given two index cells, visits all crossings between edges of those cells.
/// Terminates early and returns false if visitor_ returns false.
/// </summary>
public bool VisitCellCellCrossings(S2ShapeIndexCell a_cell, S2ShapeIndexCell b_cell)
{
// Test all edges of "a_cell" against all edges of "b_cell".
GetShapeEdges(a_index_, a_cell, a_shape_edges_);
GetShapeEdges(b_index_, b_cell, b_shape_edges_);
return(VisitEdgesEdgesCrossings(a_shape_edges_, b_shape_edges_));
}
/// <summary>
/// Appends all edges in the given S2ShapeIndexCell to the given vector.
/// </summary>
private static void AppendShapeEdges(S2ShapeIndex index, S2ShapeIndexCell cell, ShapeEdgeVector shape_edges)
{
for (int s = 0; s < cell.NumClipped(); ++s)
{
var clipped = cell.Clipped(s);
var shape = index.Shape(clipped.ShapeId);
var num_edges = clipped.NumEdges;
for (int i = 0; i < num_edges; i++)
{
shape_edges.Add(new ShapeEdge(shape, clipped.Edge(i)));
}
}
}
// Visits all crossings of any edge in "a_cell" with any index cell of B that
// is a descendant of "b_id". Terminates early and returns false if
// visitor_ returns false.
private bool VisitSubcellCrossings(S2ShapeIndexCell a_cell, S2CellId b_id)
{
// Test all edges of "a_cell" against the edges contained in B index cells
// that are descendants of "b_id".
GetShapeEdges(a_index_, a_cell, a_shape_edges_);
var b_root = new S2PaddedCell(b_id, 0);
foreach (var a in a_shape_edges_)
{
// Use an S2CrossingEdgeQuery starting at "b_root" to find the index cells
// of B that might contain crossing edges.
var result = b_query_.VisitCells(a.V0, a.V1, b_root, (S2ShapeIndexCell cell) =>
VisitEdgeCellCrossings(a, cell));
if (!result)
{
return(false);
}
}
return(true);
}
/// <summary>
/// Returns a vector containing all edges in the given S2ShapeIndexCell.
/// (The result is returned as an output parameter so that the same storage can
/// be reused, rather than allocating a new temporary vector each time.)
/// </summary>
private static void GetShapeEdges(S2ShapeIndex index, S2ShapeIndexCell cell, ShapeEdgeVector shape_edges)
{
shape_edges.Clear();
AppendShapeEdges(index, cell, shape_edges);
}
