org.elasticsearch.h3.CoordIJK Maven / Gradle / Ivy
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* under the License.
*
* This project is based on a modification of https://github.com/uber/h3 which is licensed under the Apache 2.0 License.
*
* Copyright 2016-2018, 2020-2021 Uber Technologies, Inc.
*/
package org.elasticsearch.h3;
/**
* Mutable IJK hexagon coordinates
*
* Each axis is spaced 120 degrees apart.
*
* References two Vec2d cartesian coordinate systems:
*
* 1. gnomonic: face-centered polyhedral gnomonic projection space with
* traditional scaling and x-axes aligned with the face Class II
* i-axes.
*
* 2. hex2d: local face-centered coordinate system scaled a specific H3 grid
* resolution unit length and with x-axes aligned with the local
* i-axes
*/
final class CoordIJK {
/** CoordIJK unit vectors corresponding to the 7 H3 digits.
*/
private static final int[][] UNIT_VECS = {
{ 0, 0, 0 }, // direction 0
{ 0, 0, 1 }, // direction 1
{ 0, 1, 0 }, // direction 2
{ 0, 1, 1 }, // direction 3
{ 1, 0, 0 }, // direction 4
{ 1, 0, 1 }, // direction 5
{ 1, 1, 0 } // direction 6
};
/** H3 digit representing ijk+ axes direction.
* Values will be within the lowest 3 bits of an integer.
*/
public enum Direction {
CENTER_DIGIT(0),
K_AXES_DIGIT(1),
J_AXES_DIGIT(2),
JK_AXES_DIGIT(J_AXES_DIGIT.digit() | K_AXES_DIGIT.digit()),
I_AXES_DIGIT(4),
IK_AXES_DIGIT(I_AXES_DIGIT.digit() | K_AXES_DIGIT.digit()),
IJ_AXES_DIGIT(I_AXES_DIGIT.digit() | J_AXES_DIGIT.digit()),
INVALID_DIGIT(7),
NUM_DIGITS(INVALID_DIGIT.digit()),
PENTAGON_SKIPPED_DIGIT(K_AXES_DIGIT.digit());
Direction(int digit) {
this.digit = digit;
}
private final int digit;
public int digit() {
return digit;
}
}
int i; // i component
int j; // j component
int k; // k component
CoordIJK(int i, int j, int k) {
this.i = i;
this.j = j;
this.k = k;
}
/**
* Reset the value of the IJK coordinates to the provided ones.
*
* @param i the i coordinate
* @param j the j coordinate
* @param k the k coordinate
*/
void reset(int i, int j, int k) {
this.i = i;
this.j = j;
this.k = k;
}
/**
* Find the center point in 2D cartesian coordinates of a hex.
*/
public Vec2d ijkToHex2d() {
final int i = Math.subtractExact(this.i, this.k);
final int j = Math.subtractExact(this.j, this.k);
return new Vec2d(i - 0.5 * j, j * Constants.M_SQRT3_2);
}
/**
* Find the center point in spherical coordinates of a hex on a particular icosahedral face.
*/
public LatLng ijkToGeo(int face, int res, boolean substrate) {
final int i = Math.subtractExact(this.i, this.k);
final int j = Math.subtractExact(this.j, this.k);
return Vec2d.hex2dToGeo(i - 0.5 * j, j * Constants.M_SQRT3_2, face, res, substrate);
}
/**
* Add ijk coordinates.
*
* @param i the i coordinate
* @param j the j coordinate
* @param k the k coordinate
*/
public void ijkAdd(int i, int j, int k) {
this.i = Math.addExact(this.i, i);
this.j = Math.addExact(this.j, j);
this.k = Math.addExact(this.k, k);
}
/**
* Subtract ijk coordinates.
*
* @param i the i coordinate
* @param j the j coordinate
* @param k the k coordinate
*/
public void ijkSub(int i, int j, int k) {
this.i = Math.subtractExact(this.i, i);
this.j = Math.subtractExact(this.j, j);
this.k = Math.subtractExact(this.k, k);
}
/**
* Normalizes ijk coordinates by setting the ijk coordinates
* to the smallest possible positive values.
*/
public void ijkNormalize() {
final int min = Math.min(i, Math.min(j, k));
ijkSub(min, min, min);
}
/**
* Find the normalized ijk coordinates of the hex centered on the current
* hex at the next finer aperture 7 counter-clockwise resolution.
*/
public void downAp7() {
// res r unit vectors in res r+1
// iVec (3, 0, 1)
// jVec (1, 3, 0)
// kVec (0, 1, 3)
final int i = Math.addExact(Math.multiplyExact(this.i, 3), this.j);
final int j = Math.addExact(Math.multiplyExact(this.j, 3), this.k);
final int k = Math.addExact(Math.multiplyExact(this.k, 3), this.i);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Find the normalized ijk coordinates of the hex centered on the current
* hex at the next finer aperture 7 clockwise resolution.
*/
public void downAp7r() {
// iVec (3, 1, 0)
// jVec (0, 3, 1)
// kVec (1, 0, 3)
final int i = Math.addExact(Math.multiplyExact(this.i, 3), this.k);
final int j = Math.addExact(Math.multiplyExact(this.j, 3), this.i);
final int k = Math.addExact(Math.multiplyExact(this.k, 3), this.j);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Find the normalized ijk coordinates of the hex centered on the current
* hex at the next finer aperture 3 counter-clockwise resolution.
*/
public void downAp3() {
// res r unit vectors in res r+1
// iVec (2, 0, 1)
// jVec (1, 2, 0)
// kVec (0, 1, 2)
final int i = Math.addExact(Math.multiplyExact(this.i, 2), this.j);
final int j = Math.addExact(Math.multiplyExact(this.j, 2), this.k);
final int k = Math.addExact(Math.multiplyExact(this.k, 2), this.i);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Find the normalized ijk coordinates of the hex centered on the current
* hex at the next finer aperture 3 clockwise resolution.
*/
public void downAp3r() {
// res r unit vectors in res r+1
// iVec (2, 1, 0)
// jVec (0, 2, 1)
// kVec (1, 0, 2)
final int i = Math.addExact(Math.multiplyExact(this.i, 2), this.k);
final int j = Math.addExact(Math.multiplyExact(this.j, 2), this.i);
final int k = Math.addExact(Math.multiplyExact(this.k, 2), this.j);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Rotates ijk coordinates 60 degrees clockwise.
*
*/
public void ijkRotate60cw() {
// unit vector rotations
// iVec (1, 0, 1)
// jVec (1, 1, 0)
// kVec (0, 1, 1)
final int i = Math.addExact(this.i, this.j);
final int j = Math.addExact(this.j, this.k);
final int k = Math.addExact(this.i, this.k);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Rotates ijk coordinates 60 degrees counter-clockwise.
*/
public void ijkRotate60ccw() {
// unit vector rotations
// iVec (1, 1, 0)
// jVec (0, 1, 1)
// kVec (1, 0, 1)
final int i = Math.addExact(this.i, this.k);
final int j = Math.addExact(this.i, this.j);
final int k = Math.addExact(this.j, this.k);
this.i = i;
this.j = j;
this.k = k;
ijkNormalize();
}
/**
* Find the normalized ijk coordinates of the hex in the specified digit
* direction from the current ijk coordinates.
* @param digit The digit direction from the original ijk coordinates.
*/
public void neighbor(int digit) {
if (digit > Direction.CENTER_DIGIT.digit() && digit < Direction.NUM_DIGITS.digit()) {
ijkAdd(UNIT_VECS[digit][0], UNIT_VECS[digit][1], UNIT_VECS[digit][2]);
ijkNormalize();
}
}
/**
* Find the normalized ijk coordinates of the indexing parent of a cell in a
* clockwise aperture 7 grid.
*/
public void upAp7r() {
final int i = Math.subtractExact(this.i, this.k);
final int j = Math.subtractExact(this.j, this.k);
this.i = (int) Math.round((Math.addExact(Math.multiplyExact(2, i), j)) / 7.0);
this.j = (int) Math.round((Math.subtractExact(Math.multiplyExact(3, j), i)) / 7.0);
this.k = 0;
ijkNormalize();
}
/**
* Find the normalized ijk coordinates of the indexing parent of a cell in a
* counter-clockwise aperture 7 grid.
*
*/
public void upAp7() {
final int i = Math.subtractExact(this.i, this.k);
final int j = Math.subtractExact(this.j, this.k);
this.i = (int) Math.round((Math.subtractExact(Math.multiplyExact(3, i), j)) / 7.0);
this.j = (int) Math.round((Math.addExact(Math.multiplyExact(2, j), i)) / 7.0);
this.k = 0;
ijkNormalize();
}
/**
* Determines the H3 digit corresponding to a unit vector in ijk coordinates.
*
* @return The H3 digit (0-6) corresponding to the ijk unit vector, or
* INVALID_DIGIT on failure.
*/
public int unitIjkToDigit() {
// should be call on a normalized object
if (Math.min(i, Math.min(j, k)) < 0 || Math.max(i, Math.max(j, k)) > 1) {
return Direction.INVALID_DIGIT.digit();
}
return i << 2 | j << 1 | k;
}
/**
* Rotates indexing digit 60 degrees clockwise. Returns result.
*
* @param digit Indexing digit (between 1 and 6 inclusive)
*/
public static int rotate60cw(int digit) {
return switch (digit) {
case 1 -> // K_AXES_DIGIT
Direction.JK_AXES_DIGIT.digit();
case 3 -> // JK_AXES_DIGIT:
Direction.J_AXES_DIGIT.digit();
case 2 -> // J_AXES_DIGIT:
Direction.IJ_AXES_DIGIT.digit();
case 6 -> // IJ_AXES_DIGIT
Direction.I_AXES_DIGIT.digit();
case 4 -> // I_AXES_DIGIT
Direction.IK_AXES_DIGIT.digit();
case 5 -> // IK_AXES_DIGIT
Direction.K_AXES_DIGIT.digit();
default -> digit;
};
}
/**
* Rotates indexing digit 60 degrees counter-clockwise. Returns result.
*
* @param digit Indexing digit (between 1 and 6 inclusive)
*/
public static int rotate60ccw(int digit) {
return switch (digit) {
case 1 -> // K_AXES_DIGIT
Direction.IK_AXES_DIGIT.digit();
case 5 -> // IK_AXES_DIGIT
Direction.I_AXES_DIGIT.digit();
case 4 -> // I_AXES_DIGIT
Direction.IJ_AXES_DIGIT.digit();
case 6 -> // IJ_AXES_DIGIT
Direction.J_AXES_DIGIT.digit();
case 2 -> // J_AXES_DIGIT:
Direction.JK_AXES_DIGIT.digit();
case 3 -> // JK_AXES_DIGIT:
Direction.K_AXES_DIGIT.digit();
default -> digit;
};
}
}
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