// The point 'p' does not need to be normalized.
private void Init(S2CellId id)
{
_cellId = id;
var ij = new int[2];
int?mOrientation = 0;
for (var d = 0; d < 2; ++d)
{
ij[d] = 0;
}
_face = (byte)id.ToFaceIjOrientation(ref ij[0], ref ij[1], ref mOrientation);
_orientation = (byte)mOrientation.Value; // Compress int to a byte.
_level = (byte)id.Level;
var cellSize = 1 << (S2CellId.MaxLevel - _level);
for (var d = 0; d < 2; ++d)
{
// Compute the cell bounds in scaled (i,j) coordinates.
var sijLo = (ij[d] & -cellSize) * 2 - MaxCellSize;
var sijHi = sijLo + cellSize * 2;
_uv[d][0] = S2Projections.StToUv((1.0 / MaxCellSize) * sijLo);
_uv[d][1] = S2Projections.StToUv((1.0 / MaxCellSize) * sijHi);
}
}
/**
* Convert (face, si, ti) coordinates (see s2.h) to a direction vector (not
* necessarily unit length).
*/
private static S2Point FaceSiTiToXyz(int face, int si, int ti)
{
const double kScale = 1.0 / MaxSize;
var u = S2Projections.StToUv(kScale * si);
var v = S2Projections.StToUv(kScale * ti);
return(S2Projections.FaceUvToXyz(face, u, v));
}
/**
* Return the leaf cell containing the given point (a direction vector, not
* necessarily unit length).
*/
public static S2CellId FromPoint(S2Point p)
{
var face = S2Projections.XyzToFace(p);
var uv = S2Projections.ValidFaceXyzToUv(face, p);
var i = StToIj(S2Projections.UvToSt(uv.X));
var j = StToIj(S2Projections.UvToSt(uv.Y));
return(FromFaceIj(face, i, j));
}
public bool Contains(S2Point p)
{
// We can't just call XYZtoFaceUV, because for points that lie on the
// boundary between two faces (i.e. u or v is +1/-1) we need to return
// true for both adjacent cells.
var uvPoint = S2Projections.FaceXyzToUv(_face, p);
if (uvPoint == null)
{
return(false);
}
return(uvPoint.Value.X >= _uv[0][0] && uvPoint.Value.X <= _uv[0][1] &&
uvPoint.Value.Y >= _uv[1][0] && uvPoint.Value.Y <= _uv[1][1]);
}
public S2Point GetEdgeRaw(int k)
{
switch (k)
{
case 0:
return(S2Projections.GetVNorm(_face, _uv[1][0])); // South
case 1:
return(S2Projections.GetUNorm(_face, _uv[0][1])); // East
case 2:
return(-S2Projections.GetVNorm(_face, _uv[1][1])); // North
default:
return(-S2Projections.GetUNorm(_face, _uv[0][0])); // West
}
}
/**
* Given (i, j) coordinates that may be out of bounds, normalize them by
* returning the corresponding neighbor cell on an adjacent face.
*/
private static S2CellId FromFaceIjWrap(int face, int i, int j)
{
// Convert i and j to the coordinates of a leaf cell just beyond the
// boundary of this face. This prevents 32-bit overflow in the case
// of finding the neighbors of a face cell, and also means that we
// don't need to worry about the distinction between (s,t) and (u,v).
i = Math.Max(-1, Math.Min(MaxSize, i));
j = Math.Max(-1, Math.Min(MaxSize, j));
// Find the (s,t) coordinates corresponding to (i,j). At least one
// of these coordinates will be just outside the range [0, 1].
const double kScale = 1.0 / MaxSize;
var s = kScale * ((i << 1) + 1 - MaxSize);
var t = kScale * ((j << 1) + 1 - MaxSize);
// Find the leaf cell coordinates on the adjacent face, and convert
// them to a cell id at the appropriate level.
var p = S2Projections.FaceUvToXyz(face, s, t);
face = S2Projections.XyzToFace(p);
var st = S2Projections.ValidFaceXyzToUv(face, p);
return(FromFaceIj(face, StToIj(st.X), StToIj(st.Y)));
}
private double GetLongitude(int i, int j)
{
var p = S2Projections.FaceUvToXyz(_face, _uv[0][i], _uv[1][j]);
return(Math.Atan2(p.Y, p.X));
}
// Internal method that does the actual work in the constructors.
private double GetLatitude(int i, int j)
{
var p = S2Projections.FaceUvToXyz(_face, _uv[0][i], _uv[1][j]);
return(Math.Atan2(p.Z, Math.Sqrt(p.X * p.X + p.Y * p.Y)));
}
/**
* Return the k-th vertex of the cell (k = 0,1,2,3). Vertices are returned in
* CCW order. The points returned by GetVertexRaw are not necessarily unit
* length.
*/
public S2Point GetVertexRaw(int k)
{
// Vertices are returned in the order SW, SE, NE, NW.
return(S2Projections.FaceUvToXyz(_face, _uv[0][(k >> 1) ^ (k & 1)], _uv[1][k >> 1]));
}