1 /**************************************************************************
2 * newbucket.hxx -- new bucket routines for better world modeling
4 * Written by Curtis L. Olson, started February 1999.
6 * Copyright (C) 1999 Curtis L. Olson - http://www.flightgear.org/~curt
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.
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.
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.
23 **************************************************************************/
25 /** \file newbucket.hxx
26 * A class and associated utiltity functions to manage world scenery tiling.
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.
34 #ifndef _NEWBUCKET_HXX
35 #define _NEWBUCKET_HXX
37 #include <simgear/compiler.h>
38 #include <simgear/constants.h>
39 #include <simgear/math/SGMath.hxx>
46 // #define NO_DEPRECATED_API
49 * standard size of a bucket in degrees (1/8 of a degree)
51 #define SG_BUCKET_SPAN 0.125
54 * half of a standard SG_BUCKET_SPAN
56 #define SG_HALF_BUCKET_SPAN ( 0.5 * SG_BUCKET_SPAN )
59 // return the horizontal tile span factor based on latitude
60 static double sg_bucket_span( double l ) {
63 } else if ( l >= 86.0 ) {
65 } else if ( l >= 83.0 ) {
67 } else if ( l >= 76.0 ) {
69 } else if ( l >= 62.0 ) {
71 } else if ( l >= 22.0 ) {
73 } else if ( l >= -22.0 ) {
75 } else if ( l >= -62.0 ) {
77 } else if ( l >= -76.0 ) {
79 } else if ( l >= -83.0 ) {
81 } else if ( l >= -86.0 ) {
83 } else if ( l >= -89.0 ) {
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.
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)
106 void innerSet( double dlon, double dlat );
110 * Default constructor, creates an invalid SGBucket
115 * Check if this bucket refers to a valid tile, or not.
117 bool isValid() const;
119 #ifndef NO_DEPRECATED_API
121 * Construct a bucket given a specific location.
122 * @param dlon longitude specified in degrees
123 * @param dlat latitude specified in degrees
125 SGBucket(const double dlon, const double dlat);
129 * Construct a bucket given a specific location.
131 * @param geod Geodetic location
133 SGBucket(const SGGeod& geod);
135 /** Construct a bucket given a unique bucket index number.
137 * @param bindex unique bucket index
139 SGBucket(const long int bindex);
141 #ifndef NO_DEPRECATED_API
143 * Reset a bucket to represent a new location.
145 * @param geod New geodetic location
147 void set_bucket(const SGGeod& geod);
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
155 void set_bucket( double dlon, double dlat );
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
167 * Generate the unique scenery tile index for this bucket
169 * The index is constructed as follows:
171 * 9 bits - to represent 360 degrees of longitude (-180 to 179)
172 * 8 bits - to represent 180 degrees of latitude (-90 to 89)
174 * Each 1 degree by 1 degree tile is further broken down into an 8x8
175 * grid. So we also need:
177 * 3 bits - to represent x (0 to 7)
178 * 3 bits - to represent y (0 to 7)
181 inline long int gen_index() const {
182 return ((lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x;
186 * Generate the unique scenery tile index for this bucket in ascii
188 * @return tile index in string form
190 std::string gen_index_str() const;
193 * Build the base path name for this bucket.
194 * @return base path in string form
196 std::string gen_base_path() const;
199 * @return the center lon of a tile.
201 inline double get_center_lon() const {
202 double span = sg_bucket_span( lat + y / 8.0 + SG_HALF_BUCKET_SPAN );
205 return lon + get_width() / 2.0;
207 return lon + x * span + get_width() / 2.0;
212 * @return the center lat of a tile.
214 inline double get_center_lat() const {
215 return lat + y / 8.0 + SG_HALF_BUCKET_SPAN;
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
223 double get_highest_lat() const;
226 * @return the width of the tile in degrees.
228 double get_width() const;
231 * @return the height of the tile in degrees.
233 double get_height() const;
236 * @return the width of the tile in meters.
238 double get_width_m() const;
241 * @return the height of the tile in meters.
243 double get_height_m() const;
246 * @return the center of the bucket in geodetic coordinates.
248 SGGeod get_center() const
249 { return SGGeod::fromDeg(get_center_lon(), get_center_lat()); }
252 * @return the center of the bucket in geodetic coordinates.
254 SGGeod get_corner(unsigned num) const
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());
262 // Informational methods.
265 * @return the lon of the lower left corner of
266 * the 1x1 chunk containing this tile.
268 inline int get_chunk_lon() const { return lon; }
271 * @return the lat of the lower left corner of
272 * the 1x1 chunk containing this tile.
274 inline int get_chunk_lat() const { return lat; }
277 * @return the x coord within the 1x1 degree chunk this tile.
279 inline int get_x() const { return x; }
282 * @return the y coord within the 1x1 degree chunk this tile.
284 inline int get_y() const { return y; }
287 * @return bucket offset from this by dx,dy
289 SGBucket sibling(int dx, int dy) const;
293 friend std::ostream& operator<< ( std::ostream&, const SGBucket& );
294 friend bool operator== ( const SGBucket&, const SGBucket& );
297 inline bool operator!= (const SGBucket& lhs, const SGBucket& rhs)
299 return !(lhs == rhs);
302 #ifndef NO_DEPRECATED_API
305 * Return the bucket which is offset from the specified dlon, dlat by
306 * the specified tile units in the X & Y direction.
307 * @param dlon starting lon in degrees
308 * @param dlat starting lat in degrees
309 * @param x number of bucket units to offset in x (lon) direction
310 * @param y number of bucket units to offset in y (lat) direction
311 * @return offset bucket
313 SGBucket sgBucketOffset( double dlon, double dlat, int x, int y );
319 * Calculate the offset between two buckets (in quantity of buckets).
322 * @param dx offset distance (lon) in tile units
323 * @param dy offset distance (lat) in tile units
325 void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy );
330 * retrieve a list of buckets in the given bounding box
331 * @param min min lon,lat of bounding box in degrees
332 * @param max max lon,lat of bounding box in degrees
333 * @param list standard vector of buckets within the bounding box
335 void sgGetBuckets( const SGGeod& min, const SGGeod& max, std::vector<SGBucket>& list );
338 * Write the bucket lon, lat, x, and y to the output stream.
339 * @param out output stream
342 std::ostream& operator<< ( std::ostream& out, const SGBucket& b );
345 * Compare two bucket structures for equality.
348 * @return comparison result
351 operator== ( const SGBucket& b1, const SGBucket& b2 )
353 return ( b1.lon == b2.lon &&
360 #endif // _NEWBUCKET_HXX