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>
47 * standard size of a bucket in degrees (1/8 of a degree)
49 #define SG_BUCKET_SPAN 0.125
52 * half of a standard SG_BUCKET_SPAN
54 #define SG_HALF_BUCKET_SPAN ( 0.5 * SG_BUCKET_SPAN )
57 // return the horizontal tile span factor based on latitude
58 static double sg_bucket_span( double l ) {
61 } else if ( l >= 86.0 ) {
63 } else if ( l >= 83.0 ) {
65 } else if ( l >= 76.0 ) {
67 } else if ( l >= 62.0 ) {
69 } else if ( l >= 22.0 ) {
71 } else if ( l >= -22.0 ) {
73 } else if ( l >= -62.0 ) {
75 } else if ( l >= -76.0 ) {
77 } else if ( l >= -83.0 ) {
79 } else if ( l >= -86.0 ) {
81 } else if ( l >= -89.0 ) {
90 * A class to manage world scenery tiling.
91 * This class encapsulates the world tiling scheme. It provides ways
92 * to calculate a unique tile index from a lat/lon, and it can provide
93 * information such as the dimensions of a given tile.
99 short lon; // longitude index (-180 to 179)
100 short lat; // latitude index (-90 to 89)
101 unsigned char x; // x subdivision (0 to 7)
102 unsigned char y; // y subdivision (0 to 7)
107 * Default constructor, creates an invalid SGBucket
112 * Check if this bucket refers to a valid tile, or not.
114 bool isValid() const;
117 * Construct a bucket given a specific location.
118 * @param dlon longitude specified in degrees
119 * @param dlat latitude specified in degrees
121 SGBucket(const double dlon, const double dlat);
124 * Construct a bucket given a specific location.
125 * @param dlon longitude specified in degrees
126 * @param dlat latitude specified in degrees
128 SGBucket(const SGGeod& geod);
130 /** Construct a bucket given a unique bucket index number.
131 * @param bindex unique bucket index
133 SGBucket(const long int bindex);
136 * Reset a bucket to represent a new lat and lon
137 * @param dlon longitude specified in degrees
138 * @param dlat latitude specified in degrees
140 void set_bucket(const SGGeod& geod);
143 * Reset a bucket to represent a new lat and lon
144 * @param dlon longitude specified in degrees
145 * @param dlat latitude specified in degrees
147 void set_bucket( double dlon, double dlat );
150 * Create an impossible bucket.
151 * This is useful if you are comparing cur_bucket to last_bucket
152 * and you want to make sure last_bucket starts out as something
158 * Generate the unique scenery tile index for this bucket
160 * The index is constructed as follows:
162 * 9 bits - to represent 360 degrees of longitude (-180 to 179)
163 * 8 bits - to represent 180 degrees of latitude (-90 to 89)
165 * Each 1 degree by 1 degree tile is further broken down into an 8x8
166 * grid. So we also need:
168 * 3 bits - to represent x (0 to 7)
169 * 3 bits - to represent y (0 to 7)
172 inline long int gen_index() const {
173 return ((lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x;
177 * Generate the unique scenery tile index for this bucket in ascii
179 * @return tile index in string form
181 std::string gen_index_str() const;
184 * Build the base path name for this bucket.
185 * @return base path in string form
187 std::string gen_base_path() const;
190 * @return the center lon of a tile.
192 inline double get_center_lon() const {
193 double span = sg_bucket_span( lat + y / 8.0 + SG_HALF_BUCKET_SPAN );
196 return lon + get_width() / 2.0;
198 return lon + x * span + get_width() / 2.0;
203 * @return the center lat of a tile.
205 inline double get_center_lat() const {
206 return lat + y / 8.0 + SG_HALF_BUCKET_SPAN;
210 * @return the highest (furthest from the equator) latitude of this
211 * tile. This is the top edge for tiles north of the equator, and
212 * the bottom edge for tiles south
214 double get_highest_lat() const;
217 * @return the width of the tile in degrees.
219 double get_width() const;
222 * @return the height of the tile in degrees.
224 double get_height() const;
227 * @return the width of the tile in meters.
229 double get_width_m() const;
232 * @return the height of the tile in meters.
234 double get_height_m() const;
237 * @return the center of the bucket in geodetic coordinates.
239 SGGeod get_center() const
240 { return SGGeod::fromDeg(get_center_lon(), get_center_lat()); }
243 * @return the center of the bucket in geodetic coordinates.
245 SGGeod get_corner(unsigned num) const
247 double lonFac = ((num + 1) & 2) ? 0.5 : -0.5;
248 double latFac = ((num ) & 2) ? 0.5 : -0.5;
249 return SGGeod::fromDeg(get_center_lon() + lonFac*get_width(),
250 get_center_lat() + latFac*get_height());
253 // Informational methods.
256 * @return the lon of the lower left corner of
257 * the 1x1 chunk containing this tile.
259 inline int get_chunk_lon() const { return lon; }
262 * @return the lat of the lower left corner of
263 * the 1x1 chunk containing this tile.
265 inline int get_chunk_lat() const { return lat; }
268 * @return the x coord within the 1x1 degree chunk this tile.
270 inline int get_x() const { return x; }
273 * @return the y coord within the 1x1 degree chunk this tile.
275 inline int get_y() const { return y; }
278 * @return bucket offset from this by dx,dy
280 SGBucket sibling(int dx, int dy) const;
284 friend std::ostream& operator<< ( std::ostream&, const SGBucket& );
285 friend bool operator== ( const SGBucket&, const SGBucket& );
288 inline bool operator!= (const SGBucket& lhs, const SGBucket& rhs)
290 return !(lhs == rhs);
296 * Return the bucket which is offset from the specified dlon, dlat by
297 * the specified tile units in the X & Y direction.
298 * @param dlon starting lon in degrees
299 * @param dlat starting lat in degrees
300 * @param x number of bucket units to offset in x (lon) direction
301 * @param y number of bucket units to offset in y (lat) direction
302 * @return offset bucket
304 SGBucket sgBucketOffset( double dlon, double dlat, int x, int y );
309 * Calculate the offset between two buckets (in quantity of buckets).
312 * @param dx offset distance (lon) in tile units
313 * @param dy offset distance (lat) in tile units
315 void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy );
320 * retrieve a list of buckets in the given bounding box
321 * @param min min lon,lat of bounding box in degrees
322 * @param max max lon,lat of bounding box in degrees
323 * @param list standard vector of buckets within the bounding box
325 void sgGetBuckets( const SGGeod& min, const SGGeod& max, std::vector<SGBucket>& list );
328 * Write the bucket lon, lat, x, and y to the output stream.
329 * @param out output stream
332 std::ostream& operator<< ( std::ostream& out, const SGBucket& b );
335 * Compare two bucket structures for equality.
338 * @return comparison result
341 operator== ( const SGBucket& b1, const SGBucket& b2 )
343 return ( b1.lon == b2.lon &&
350 #endif // _NEWBUCKET_HXX