public void Test_GetPerimeter_WrongDimension()
{
Assert.Equal(S1Angle.Zero,
S2.GetPerimeter(MakeIndexOrDie("0:0 # #").Shape(0)));
Assert.Equal(S1Angle.Zero,
S2ShapeIndexMeasures.GetPerimeter(MakeIndexOrDie("0:0, 0:1, 1:0")));
}
public void Test_GetPerimeter_MoreThanTwoPi()
{
// Make sure that GetPerimeter doesn't use S1ChordAngle, which can only
// represent distances up to 2*Pi.
var loop = ParsePointsOrDie("0:0, 0:90, 0:180, 90:0, 0:-90").ToArray();
Assert2.DoubleEqual(5 * S2.M_PI_2, S2.GetPerimeter(loop).Radians);
}
// Returns the total perimeter of all polygons in the index (including both
// "shells" and "holes"). Returns zero if no polygons are present.
//
// All edges are modeled as spherical geodesics. The result can be converted
// to a distance on the Earth's surface (with a worst-case error of 0.562%
// near the equator) using the functions in s2earth.h.
public static S1Angle GetPerimeter(S2ShapeIndex index)
{
var perimeter = S1Angle.Zero;
for (int i = 0; i < index.NumShapeIds(); ++i)
{
var shape = index.Shape(i);
if (shape != null)
{
perimeter += S2.GetPerimeter(shape);
}
}
return(perimeter);
}
// For shapes of dimension 2, returns the sum of all loop perimeters on the
// unit sphere. Otherwise returns zero. (See GetLength for shapes of
// dimension 1.)
//
// All edges are modeled as spherical geodesics. The result can be converted
// to a distance on the Earth's surface (with a worst-case error of 0.562%
// near the equator) using the functions in s2earth.h.
public static S1Angle GetPerimeter(S2Shape shape)
{
if (shape.Dimension() != 2)
{
return(S1Angle.Zero);
}
var perimeter = S1Angle.Zero;
int num_chains = shape.NumChains();
for (int chain_id = 0; chain_id < num_chains; ++chain_id)
{
GetChainVertices(shape, chain_id, out var vertices);
perimeter += S2.GetPerimeter(vertices);
}
return(perimeter);
}
public void Test_GetPerimeter_Octant()
{
var loop = ParsePointsOrDie("0:0, 0:90, 90:0");
Assert2.DoubleEqual(3 * S2.M_PI_2, S2.GetPerimeter(loop.ToArray()).Radians);
}
public void Test_GetPerimeter_Empty()
{
Assert.Equal(S1Angle.Zero, S2.GetPerimeter(Array.Empty <S2Point>()));
}
public void Test_GetPerimeter_TwoLoopPolygon()
{
// To ensure that all edges are 1 degree long, we use degenerate loops.
Assert.Equal(S1Angle.FromDegrees(6),
S2.GetPerimeter(MakeLaxPolygonOrDie("0:0, 1:0; 0:1, 0:2, 0:3")));
}
public void Test_GetPerimeter_FullPolygon()
{
Assert.Equal(S1Angle.Zero, S2.GetPerimeter(MakeLaxPolygonOrDie("full")));
}
public void Test_GetPerimeter_EmptyPolygon()
{
Assert.Equal(S1Angle.Zero, S2.GetPerimeter(MakeLaxPolygonOrDie("empty")));
}