// 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));
}
