1/*
2 * Copyright 2016-2018 Uber Technologies, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16/** @file coordijk.h
17 * @brief Header file for CoordIJK functions including conversion from lat/lon
18 *
19 * References two Vec2d cartesian coordinate systems:
20 *
21 * 1. gnomonic: face-centered polyhedral gnomonic projection space with
22 * traditional scaling and x-axes aligned with the face Class II
23 * i-axes.
24 *
25 * 2. hex2d: local face-centered coordinate system scaled a specific H3 grid
26 * resolution unit length and with x-axes aligned with the local
27 * i-axes
28 */
29
30#ifndef COORDIJK_H
31#define COORDIJK_H
32
33#include "geoCoord.h"
34#include "h3api.h"
35#include "vec2d.h"
36
37/** @struct CoordIJK
38 * @brief IJK hexagon coordinates
39 *
40 * Each axis is spaced 120 degrees apart.
41 */
42typedef struct {
43 int i; ///< i component
44 int j; ///< j component
45 int k; ///< k component
46} CoordIJK;
47
48/** @brief CoordIJK unit vectors corresponding to the 7 H3 digits.
49 */
50static const CoordIJK UNIT_VECS[] = {
51 {0, 0, 0}, // direction 0
52 {0, 0, 1}, // direction 1
53 {0, 1, 0}, // direction 2
54 {0, 1, 1}, // direction 3
55 {1, 0, 0}, // direction 4
56 {1, 0, 1}, // direction 5
57 {1, 1, 0} // direction 6
58};
59
60/** @brief H3 digit representing ijk+ axes direction.
61 * Values will be within the lowest 3 bits of an integer.
62 */
63typedef enum {
64 /** H3 digit in center */
65 CENTER_DIGIT = 0,
66 /** H3 digit in k-axes direction */
67 K_AXES_DIGIT = 1,
68 /** H3 digit in j-axes direction */
69 J_AXES_DIGIT = 2,
70 /** H3 digit in j == k direction */
71 JK_AXES_DIGIT = J_AXES_DIGIT | K_AXES_DIGIT, /* 3 */
72 /** H3 digit in i-axes direction */
73 I_AXES_DIGIT = 4,
74 /** H3 digit in i == k direction */
75 IK_AXES_DIGIT = I_AXES_DIGIT | K_AXES_DIGIT, /* 5 */
76 /** H3 digit in i == j direction */
77 IJ_AXES_DIGIT = I_AXES_DIGIT | J_AXES_DIGIT, /* 6 */
78 /** H3 digit in the invalid direction */
79 INVALID_DIGIT = 7,
80 /** Valid digits will be less than this value. Same value as INVALID_DIGIT.
81 */
82 NUM_DIGITS = INVALID_DIGIT
83} Direction;
84
85// Internal functions
86
87void _setIJK(CoordIJK* ijk, int i, int j, int k);
88void _hex2dToCoordIJK(const Vec2d* v, CoordIJK* h);
89void _ijkToHex2d(const CoordIJK* h, Vec2d* v);
90int _ijkMatches(const CoordIJK* c1, const CoordIJK* c2);
91void _ijkAdd(const CoordIJK* h1, const CoordIJK* h2, CoordIJK* sum);
92void _ijkSub(const CoordIJK* h1, const CoordIJK* h2, CoordIJK* diff);
93void _ijkScale(CoordIJK* c, int factor);
94void _ijkNormalize(CoordIJK* c);
95Direction _unitIjkToDigit(const CoordIJK* ijk);
96void _upAp7(CoordIJK* ijk);
97void _upAp7r(CoordIJK* ijk);
98void _downAp7(CoordIJK* ijk);
99void _downAp7r(CoordIJK* ijk);
100void _downAp3(CoordIJK* ijk);
101void _downAp3r(CoordIJK* ijk);
102void _neighbor(CoordIJK* ijk, Direction digit);
103void _ijkRotate60ccw(CoordIJK* ijk);
104void _ijkRotate60cw(CoordIJK* ijk);
105Direction _rotate60ccw(Direction digit);
106Direction _rotate60cw(Direction digit);
107int ijkDistance(const CoordIJK* a, const CoordIJK* b);
108void ijkToIj(const CoordIJK* ijk, CoordIJ* ij);
109void ijToIjk(const CoordIJ* ij, CoordIJK* ijk);
110void ijkToCube(CoordIJK* ijk);
111void cubeToIjk(CoordIJK* ijk);
112
113#endif
114