/// <summary>
/// Produces ijk+ coordinates for an index anchored by an origin.
///
/// The coordinate space used by this function may have deleted
/// regions or warping due to pentagonal distortion.
///
/// Coordinates are only comparable if they come from the same
/// origin index.
///
/// Failure may occur if the index is too far away from the origin
/// or if the index is on the other side of a pentagon.
/// </summary>
/// <param name="origin">An anchoring index for the ijk+ coordinate system</param>
/// <param name="h3">Index to find the coordinates of</param>
/// <param name="out_coord">ijk+ coordinates of the index will be placed here on success</param>
/// <returns>0 on success, or another value on failure.</returns>
/// <!-- Based off 3.2.0 -->
static int h3ToLocalIjk(H3Index origin, H3Index h3, ref CoordIJK out_coord)
{
int res = H3Index.H3_GET_RESOLUTION(origin);
if (res != H3Index.H3_GET_RESOLUTION(h3))
{
return(1);
}
int originBaseCell = H3Index.H3_GET_BASE_CELL(origin);
int baseCell = H3Index.H3_GET_BASE_CELL(h3);
// Direction from origin base cell to index base cell
Direction dir = 0;
Direction revDir = 0;
if (originBaseCell != baseCell)
{
dir = BaseCells._getBaseCellDirection(originBaseCell, baseCell);
if (dir == Direction.INVALID_DIGIT)
{
// Base cells are not neighbors, can't unfold.
return(2);
}
revDir = BaseCells._getBaseCellDirection(baseCell, originBaseCell);
if (revDir == Direction.INVALID_DIGIT)
{
throw new Exception("assert(revDir != INVALID_DIGIT)");
}
}
int originOnPent = (BaseCells._isBaseCellPentagon(originBaseCell)
? 1
: 0);
int indexOnPent = (BaseCells._isBaseCellPentagon(baseCell)
? 1
: 0);
FaceIJK indexFijk = new FaceIJK();
if (dir != Direction.CENTER_DIGIT)
{
// Rotate index into the orientation of the origin base cell.
// cw because we are undoing the rotation into that base cell.
int baseCellRotations = BaseCells.baseCellNeighbor60CCWRots[originBaseCell, (int)dir];
if (indexOnPent != 0)
{
for (int i = 0; i < baseCellRotations; i++)
{
h3 = H3Index._h3RotatePent60cw(h3);
revDir = CoordIJK._rotate60cw(revDir);
if (revDir == Direction.K_AXES_DIGIT)
{
revDir = CoordIJK._rotate60cw(revDir);
}
}
}
else
{
for (int i = 0; i < baseCellRotations; i++)
{
h3 = H3Index._h3Rotate60cw(ref h3);
revDir = CoordIJK._rotate60cw(revDir);
}
}
}
// Face is unused. This produces coordinates in base cell coordinate space.
H3Index._h3ToFaceIjkWithInitializedFijk(h3, ref indexFijk);
if (dir != Direction.CENTER_DIGIT)
{
if (baseCell == originBaseCell)
{
throw new Exception("assert(baseCell != originBaseCell);");
}
if ((originOnPent != 0) && (indexOnPent != 0))
{
throw new Exception("assert(!(originOnPent && indexOnPent));");
}
int pentagonRotations = 0;
int directionRotations = 0;
if (originOnPent != 0)
{
int originLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(origin);
if ((H3Index.isResClassIII(res) &&
FAILED_DIRECTIONS_III[originLeadingDigit, (int)dir]) ||
(!H3Index.isResClassIII(res) &&
FAILED_DIRECTIONS_II[originLeadingDigit, (int)dir]))
{
// TODO this part of the pentagon might not be unfolded
// correctly.
return(3);
}
directionRotations = PENTAGON_ROTATIONS[originLeadingDigit, (int)dir];
pentagonRotations = directionRotations;
}
else if (indexOnPent != 0)
{
int indexLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(h3);
if ((H3Index.isResClassIII(res) &&
FAILED_DIRECTIONS_III[indexLeadingDigit, (int)revDir]) ||
(!H3Index.isResClassIII(res) &&
FAILED_DIRECTIONS_II[indexLeadingDigit, (int)revDir]))
{
// TODO this part of the pentagon might not be unfolded
// correctly.
return(4);
}
pentagonRotations = PENTAGON_ROTATIONS[(int)revDir, indexLeadingDigit];
}
if (pentagonRotations < 0)
{
throw new Exception("assert(pentagonRotations >= 0);");
}
if (directionRotations < 0)
{
throw new Exception("assert(directionRotations >= 0);");
}
for (int i = 0; i < pentagonRotations; i++)
{
CoordIJK._ijkRotate60cw(ref indexFijk.coord);
}
CoordIJK offset = new CoordIJK();
CoordIJK._neighbor(ref offset, dir);
// Scale offset based on resolution
for (int r = res - 1; r >= 0; r--)
{
if (H3Index.isResClassIII(r + 1))
{
// rotate ccw
CoordIJK._downAp7(ref offset);
}
else
{
// rotate cw
CoordIJK._downAp7r(ref offset);
}
}
for (int i = 0; i < directionRotations; i++)
{
CoordIJK._ijkRotate60cw(ref offset);
}
// Perform necessary translation
CoordIJK._ijkAdd(indexFijk.coord, offset, ref indexFijk.coord);
CoordIJK._ijkNormalize(ref indexFijk.coord);
}
else if (originOnPent != 0 && indexOnPent != 0)
{
// If the origin and index are on pentagon, and we checked that the base
// cells are the same or neighboring, then they must be the same base
// cell.
if (baseCell != originBaseCell)
{
throw new Exception("assert(baseCell == originBaseCell);");
}
int originLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(origin);
int indexLeadingDigit = (int)H3Index._h3LeadingNonZeroDigit(h3);
if (FAILED_DIRECTIONS_III[originLeadingDigit, indexLeadingDigit] ||
FAILED_DIRECTIONS_II[originLeadingDigit, indexLeadingDigit])
{
// TODO this part of the pentagon might not be unfolded
// correctly.
return(5);
}
int withinPentagonRotations =
PENTAGON_ROTATIONS[originLeadingDigit, indexLeadingDigit];
for (int i = 0; i < withinPentagonRotations; i++)
{
CoordIJK._ijkRotate60cw(ref indexFijk.coord);
}
}
out_coord = indexFijk.coord;
return(0);
}
/// <summary>
/// Returns the hexagon index neighboring the origin, in the direction dir.
///
/// Implementation note: The only reachable case where this returns 0 is if the
/// origin is a pentagon and the translation is in the k direction. Thus,
/// 0 can only be returned if origin is a pentagon.
/// </summary>
/// <param name="origin">Origin index</param>
/// <param name="dir">Direction to move in</param>
/// <param name="rotations">
/// Number of ccw rotations to perform to reorient the translation vector.
/// Will be modified to the new number of rotations to perform (such as
/// when crossing a face edge.)
/// </param>
/// <returns>H3Index of the specified neighbor or 0 if deleted k-subsequence distortion is encountered.</returns>
/// <!-- Based off 3.2.0 -->
internal static ulong h3NeighborRotations(H3Index origin, Direction dir, ref int rotations)
{
H3Index out_hex = origin;
for (int i = 0; i < rotations; i++)
{
dir = CoordIJK._rotate60ccw(dir);
}
int newRotations = 0;
int oldBaseCell = H3Index.H3_GET_BASE_CELL(out_hex);
Direction oldLeadingDigit = H3Index._h3LeadingNonZeroDigit(out_hex);
// Adjust the indexing digits and, if needed, the base cell.
int r = H3Index.H3_GET_RESOLUTION(out_hex) - 1;
while (true)
{
if (r == -1)
{
H3Index.H3_SET_BASE_CELL(ref out_hex, BaseCells.baseCellNeighbors[oldBaseCell, (int)dir]);
newRotations = BaseCells.baseCellNeighbor60CCWRots[oldBaseCell, (int)dir];
if (H3Index.H3_GET_BASE_CELL(out_hex) == BaseCells.INVALID_BASE_CELL)
{
// Adjust for the deleted k vertex at the base cell level.
// This edge actually borders a different neighbor.
H3Index.H3_SET_BASE_CELL(ref out_hex,
BaseCells.baseCellNeighbors[oldBaseCell, (int)Direction.IK_AXES_DIGIT]);
newRotations =
BaseCells.baseCellNeighbor60CCWRots[oldBaseCell, (int)Direction.IK_AXES_DIGIT];
// perform the adjustment for the k-subsequence we're skipping
// over.
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
rotations++;
}
break;
}
Direction oldDigit = H3Index.H3_GET_INDEX_DIGIT(out_hex, r + 1);
Direction nextDir;
if (H3Index.isResClassIII(r + 1))
{
H3Index.H3_SET_INDEX_DIGIT(ref out_hex, r + 1, (ulong)NEW_DIGIT_II[(int)oldDigit, (int)dir]);
nextDir = NEW_ADJUSTMENT_II[(int)oldDigit, (int)dir];
}
else
{
H3Index.H3_SET_INDEX_DIGIT(ref out_hex, r + 1,
(ulong)NEW_DIGIT_III[(int)oldDigit, (int)dir]);
nextDir = NEW_ADJUSTMENT_III[(int)oldDigit, (int)dir];
}
if (nextDir != Direction.CENTER_DIGIT)
{
dir = nextDir;
r--;
}
else
{
// No more adjustment to perform
break;
}
}
int newBaseCell = H3Index.H3_GET_BASE_CELL(out_hex);
if (BaseCells._isBaseCellPentagon(newBaseCell))
{
int alreadyAdjustedKSubsequence = 0;
// force rotation out of missing k-axes sub-sequence
if (H3Index._h3LeadingNonZeroDigit(out_hex) == Direction.K_AXES_DIGIT)
{
if (oldBaseCell != newBaseCell)
{
// in this case, we traversed into the deleted
// k subsequence of a pentagon base cell.
// We need to rotate out of that case depending
// on how we got here.
// check for a cw/ccw offset face; default is ccw
if (BaseCells._baseCellIsCwOffset(
newBaseCell, BaseCells.baseCellData[oldBaseCell].homeFijk.face))
{
out_hex = H3Index._h3Rotate60cw(ref out_hex);
}
else
{
out_hex = H3Index._h3Rotate60ccw(ref out_hex); // LCOV_EXCL_LINE
}
// See cwOffsetPent in testKRing.c for why this is
// unreachable.
alreadyAdjustedKSubsequence = 1;
}
else
{
// In this case, we traversed into the deleted
// k subsequence from within the same pentagon
// base cell.
if (oldLeadingDigit == Direction.CENTER_DIGIT)
{
// Undefined: the k direction is deleted from here
return(H3Index.H3_INVALID_INDEX);
}
switch (oldLeadingDigit)
{
case Direction.JK_AXES_DIGIT:
// Rotate out of the deleted k subsequence
// We also need an additional change to the direction we're
// moving in
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
rotations++;
break;
case Direction.IK_AXES_DIGIT:
// Rotate out of the deleted k subsequence
// We also need an additional change to the direction we're
// moving in
out_hex = H3Index._h3Rotate60cw(ref out_hex);
rotations += 5;
break;
default:
// Should never occur
return(H3Index.H3_INVALID_INDEX); // LCOV_EXCL_LINE
}
}
}
for (int i = 0; i < newRotations; i++)
{
out_hex = H3Index._h3RotatePent60ccw(ref out_hex);
}
// Account for differing orientation of the base cells (this edge
// might not follow properties of some other edges.)
if (oldBaseCell != newBaseCell)
{
if (BaseCells._isBaseCellPolarPentagon(newBaseCell))
{
// 'polar' base cells behave differently because they have all
// i neighbors.
if (oldBaseCell != 118 && oldBaseCell != 8 &&
H3Index._h3LeadingNonZeroDigit(out_hex) != Direction.JK_AXES_DIGIT)
{
rotations++;
}
}
else if (H3Index._h3LeadingNonZeroDigit(out_hex) == Direction.IK_AXES_DIGIT &&
alreadyAdjustedKSubsequence == 0)
{
// account for distortion introduced to the 5 neighbor by the
// deleted k subsequence.
rotations++;
}
}
}
else
{
for (int i = 0; i < newRotations; i++)
{
out_hex = H3Index._h3Rotate60ccw(ref out_hex);
}
}
rotations = (rotations + newRotations) % 6;
return(out_hex);
}
