1 /**************************************************************************
2 * newbucket.hxx -- new bucket routines for better world modeling
3 *
4 * Written by Curtis L. Olson, started February 1999.
5 *
6 * Copyright (C) 1999 Curtis L. Olson - http://www.flightgear.org/~curt
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21 *
22 * $Id$
23 **************************************************************************/
24
25 /** \file newbucket.hxx
26 * A class and associated utiltity functions to manage world scenery tiling.
27 *
28 * Tile borders are aligned along circles of latitude and longitude.
29 * All tiles are 1/8 degree of latitude high and their width in degrees
30 * longitude depends on their latitude, adjusted in such a way that
31 * all tiles cover about the same amount of area of the earth surface.
32 */
33
34 #ifndef _NEWBUCKET_HXX
35 #define _NEWBUCKET_HXX
36
37 #include <simgear/compiler.h>
38 #include <simgear/constants.h>
39 #include <simgear/math/SGMath.hxx>
40
41 #include <cmath>
42 #include <string>
43 #include <iosfwd>
44 #include <vector>
45
46 // #define NO_DEPRECATED_API
47
48 /**
49 * standard size of a bucket in degrees (1/8 of a degree)
50 */
51 #define SG_BUCKET_SPAN 0.125
52
53 /**
54 * half of a standard SG_BUCKET_SPAN
55 */
56 #define SG_HALF_BUCKET_SPAN ( 0.5 * SG_BUCKET_SPAN )
57
58
59 // return the horizontal tile span factor based on latitude
sg_bucket_span(double l)60 static double sg_bucket_span( double l ) {
61 if ( l >= 89.0 ) {
62 return 12.0;
63 } else if ( l >= 86.0 ) {
64 return 4.0;
65 } else if ( l >= 83.0 ) {
66 return 2.0;
67 } else if ( l >= 76.0 ) {
68 return 1.0;
69 } else if ( l >= 62.0 ) {
70 return 0.5;
71 } else if ( l >= 22.0 ) {
72 return 0.25;
73 } else if ( l >= -22.0 ) {
74 return 0.125;
75 } else if ( l >= -62.0 ) {
76 return 0.25;
77 } else if ( l >= -76.0 ) {
78 return 0.5;
79 } else if ( l >= -83.0 ) {
80 return 1.0;
81 } else if ( l >= -86.0 ) {
82 return 2.0;
83 } else if ( l >= -89.0 ) {
84 return 4.0;
85 } else {
86 return 12.0;
87 }
88 }
89
90
91 /**
92 * A class to manage world scenery tiling.
93 * This class encapsulates the world tiling scheme. It provides ways
94 * to calculate a unique tile index from a lat/lon, and it can provide
95 * information such as the dimensions of a given tile.
96 */
97
98 class SGBucket {
99
100 private:
101 short lon; // longitude index (-180 to 179)
102 short lat; // latitude index (-90 to 89)
103 unsigned char x; // x subdivision (0 to 7)
104 unsigned char y; // y subdivision (0 to 7)
105
106 void innerSet( double dlon, double dlat );
107 public:
108
109 /**
110 * Default constructor, creates an invalid SGBucket
111 */
112 SGBucket();
113
114 /**
115 * Check if this bucket refers to a valid tile, or not.
116 */
117 bool isValid() const;
118
119 #ifndef NO_DEPRECATED_API
120 /**
121 * Construct a bucket given a specific location.
122 * @param dlon longitude specified in degrees
123 * @param dlat latitude specified in degrees
124 */
125 SGBucket(const double dlon, const double dlat);
126 #endif
127
128 /**
129 * Construct a bucket given a specific location.
130 *
131 * @param geod Geodetic location
132 */
133 SGBucket(const SGGeod& geod);
134
135 /** Construct a bucket given a unique bucket index number.
136 *
137 * @param bindex unique bucket index
138 */
139 SGBucket(const long int bindex);
140
141 #ifndef NO_DEPRECATED_API
142 /**
143 * Reset a bucket to represent a new location.
144 *
145 * @param geod New geodetic location
146 */
147 void set_bucket(const SGGeod& geod);
148
149
150 /**
151 * Reset a bucket to represent a new lat and lon
152 * @param dlon longitude specified in degrees
153 * @param dlat latitude specified in degrees
154 */
155 void set_bucket( double dlon, double dlat );
156 #endif
157
158 /**
159 * Create an impossible bucket.
160 * This is useful if you are comparing cur_bucket to last_bucket
161 * and you want to make sure last_bucket starts out as something
162 * impossible.
163 */
164 void make_bad();
165
166 /**
167 * Generate the unique scenery tile index for this bucket
168 *
169 * The index is constructed as follows:
170 *
171 * 9 bits - to represent 360 degrees of longitude (-180 to 179)
172 * 8 bits - to represent 180 degrees of latitude (-90 to 89)
173 *
174 * Each 1 degree by 1 degree tile is further broken down into an 8x8
175 * grid. So we also need:
176 *
177 * 3 bits - to represent x (0 to 7)
178 * 3 bits - to represent y (0 to 7)
179 * @return tile index
180 */
gen_index() const181 inline long int gen_index() const {
182 return ((lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x;
183 }
184
185 /**
186 * Generate the unique scenery tile index for this bucket in ascii
187 * string form.
188 * @return tile index in string form
189 */
190 std::string gen_index_str() const;
191
192 /**
193 * Build the base path name for this bucket.
194 * @return base path in string form
195 */
196 std::string gen_base_path() const;
197
198 /**
199 * @return the center lon of a tile.
200 */
get_center_lon() const201 inline double get_center_lon() const {
202 double span = sg_bucket_span( lat + y / 8.0 + SG_HALF_BUCKET_SPAN );
203
204 if ( span >= 1.0 ) {
205 return lon + get_width() / 2.0;
206 } else {
207 return lon + x * span + get_width() / 2.0;
208 }
209 }
210
211 /**
212 * @return the center lat of a tile.
213 */
get_center_lat() const214 inline double get_center_lat() const {
215 return lat + y / 8.0 + SG_HALF_BUCKET_SPAN;
216 }
217
218 /**
219 * @return the highest (furthest from the equator) latitude of this
220 * tile. This is the top edge for tiles north of the equator, and
221 * the bottom edge for tiles south
222 */
223 double get_highest_lat() const;
224
225 /**
226 * @return the width of the tile in degrees.
227 */
228 double get_width() const;
229
230 /**
231 * @return the height of the tile in degrees.
232 */
233 double get_height() const;
234
235 /**
236 * @return the width of the tile in meters.
237 */
238 double get_width_m() const;
239
240 /**
241 * @return the height of the tile in meters.
242 */
243 double get_height_m() const;
244
245 /**
246 * @return the center of the bucket in geodetic coordinates.
247 */
get_center() const248 SGGeod get_center() const
249 { return SGGeod::fromDeg(get_center_lon(), get_center_lat()); }
250
251 /**
252 * @return the center of the bucket in geodetic coordinates.
253 */
get_corner(unsigned num) const254 SGGeod get_corner(unsigned num) const
255 {
256 double lonFac = ((num + 1) & 2) ? 0.5 : -0.5;
257 double latFac = ((num ) & 2) ? 0.5 : -0.5;
258 return SGGeod::fromDeg(get_center_lon() + lonFac*get_width(),
259 get_center_lat() + latFac*get_height());
260 }
261
262 // Informational methods.
263
264 /**
265 * @return the lon of the lower left corner of
266 * the 1x1 chunk containing this tile.
267 */
get_chunk_lon() const268 inline int get_chunk_lon() const { return lon; }
269
270 /**
271 * @return the lat of the lower left corner of
272 * the 1x1 chunk containing this tile.
273 */
get_chunk_lat() const274 inline int get_chunk_lat() const { return lat; }
275
276 /**
277 * @return the x coord within the 1x1 degree chunk this tile.
278 */
get_x() const279 inline int get_x() const { return x; }
280
281 /**
282 * @return the y coord within the 1x1 degree chunk this tile.
283 */
get_y() const284 inline int get_y() const { return y; }
285
286 /**
287 * @return bucket offset from this by dx,dy
288 */
289 SGBucket sibling(int dx, int dy) const;
290
291 /**
292 * @return multiple buckets offset from this by dx,dy
293 */
294 unsigned int siblings(int dz, int dy, std::vector<SGBucket>& buckets) const;
295
296 // friends
297
298 friend std::ostream& operator<< ( std::ostream&, const SGBucket& );
299 friend bool operator== ( const SGBucket&, const SGBucket& );
300 };
301
operator !=(const SGBucket & lhs,const SGBucket & rhs)302 inline bool operator!= (const SGBucket& lhs, const SGBucket& rhs)
303 {
304 return !(lhs == rhs);
305 }
306
307 #ifndef NO_DEPRECATED_API
308 /**
309 * \relates SGBucket
310 * Return the bucket which is offset from the specified dlon, dlat by
311 * the specified tile units in the X & Y direction.
312 * @param dlon starting lon in degrees
313 * @param dlat starting lat in degrees
314 * @param x number of bucket units to offset in x (lon) direction
315 * @param y number of bucket units to offset in y (lat) direction
316 * @return offset bucket
317 */
318 SGBucket sgBucketOffset( double dlon, double dlat, int x, int y );
319 #endif
320
321
322 /**
323 * \relates SGBucket
324 * Calculate the offset between two buckets (in quantity of buckets).
325 * @param b1 bucket 1
326 * @param b2 bucket 2
327 * @param dx offset distance (lon) in tile units
328 * @param dy offset distance (lat) in tile units
329 */
330 void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy );
331
332
333 /**
334 * \relates SGBucket
335 * retrieve a list of buckets in the given bounding box
336 * @param min min lon,lat of bounding box in degrees
337 * @param max max lon,lat of bounding box in degrees
338 * @param list standard vector of buckets within the bounding box
339 */
340 void sgGetBuckets( const SGGeod& min, const SGGeod& max, std::vector<SGBucket>& list );
341
342 /**
343 * Write the bucket lon, lat, x, and y to the output stream.
344 * @param out output stream
345 * @param b bucket
346 */
347 std::ostream& operator<< ( std::ostream& out, const SGBucket& b );
348
349 /**
350 * Compare two bucket structures for equality.
351 * @param b1 bucket 1
352 * @param b2 bucket 2
353 * @return comparison result
354 */
355 inline bool
operator ==(const SGBucket & b1,const SGBucket & b2)356 operator== ( const SGBucket& b1, const SGBucket& b2 )
357 {
358 return ( b1.lon == b2.lon &&
359 b1.lat == b2.lat &&
360 b1.x == b2.x &&
361 b1.y == b2.y );
362 }
363
364
365 #endif // _NEWBUCKET_HXX
366
367
368