// Converts a 1-dimensional S2Shape into an S2Polyline. Converts the first
// chain in the shape to a vector of S2Point vertices and uses that to construct
// the S2Polyline. Note that the input 1-dimensional S2Shape must contain at
// most 1 chain, and that this method does not accept an empty shape (i.e. a
// shape with no vertices).
public static S2Polyline ShapeToS2Polyline(S2Shape line)
{
System.Diagnostics.Debug.Assert(line.Dimension() == 1);
System.Diagnostics.Debug.Assert(line.NumChains() == 1);
S2Point[] vertices;
S2.GetChainVertices(line, 0, out vertices);
return new S2Polyline(vertices);
}
// Converts a 2-dimensional S2Shape into an S2Polygon. Each chain is converted
// to an S2Loop and the vector of loops is used to construct the S2Polygon.
public static S2Polygon ShapeToS2Polygon(S2Shape poly)
{
if (poly.IsFull())
{
return new S2Polygon(S2Loop.kFull);
}
System.Diagnostics.Debug.Assert(poly.Dimension() == 2);
List<S2Loop> loops = new();
for (int i = 0; i < poly.NumChains(); ++i)
{
S2.GetChainVertices(poly, i, out var vertices);
loops.Add(new S2Loop(vertices));
}
var output_poly = new S2Polygon(loops, initOriented: true);
return output_poly;
}