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>
42 #include <cstdio> // sprintf()
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 char x; // x subdivision (0 to 7)
102 char y; // y subdivision (0 to 7)
107 * Default constructor.
112 * Construct a bucket given a specific location.
113 * @param dlon longitude specified in degrees
114 * @param dlat latitude specified in degrees
116 SGBucket(const double dlon, const double dlat);
119 * Construct a bucket given a specific location.
120 * @param dlon longitude specified in degrees
121 * @param dlat latitude specified in degrees
123 SGBucket(const SGGeod& geod);
125 /** Construct a bucket.
126 * @param is_good if false, create an invalid bucket. This is
127 * useful * if you are comparing cur_bucket to last_bucket and
128 * you want to * make sure last_bucket starts out as something
131 SGBucket(const bool is_good);
133 /** Construct a bucket given a unique bucket index number.
134 * @param bindex unique bucket index
136 SGBucket(const long int bindex);
139 * Reset a bucket to represent a new lat and lon
140 * @param dlon longitude specified in degrees
141 * @param dlat latitude specified in degrees
143 void set_bucket( double dlon, double dlat );
146 * Reset a bucket to represent a new lat and lon
147 * @param lonlat an array of double[2] holding lon and lat
148 * (specified) in degrees
150 void set_bucket( double *lonlat );
153 * Reset a bucket to represent a new lat and lon
154 * @param dlon longitude specified in degrees
155 * @param dlat latitude specified in degrees
157 void set_bucket(const SGGeod& geod);
160 * Create an impossible bucket.
161 * This is useful if you are comparing cur_bucket to last_bucket
162 * and you want to make sure last_bucket starts out as something
165 inline void make_bad() {
166 set_bucket(0.0, 0.0);
171 * Generate the unique scenery tile index for this bucket
173 * The index is constructed as follows:
175 * 9 bits - to represent 360 degrees of longitude (-180 to 179)
176 * 8 bits - to represent 180 degrees of latitude (-90 to 89)
178 * Each 1 degree by 1 degree tile is further broken down into an 8x8
179 * grid. So we also need:
181 * 3 bits - to represent x (0 to 7)
182 * 3 bits - to represent y (0 to 7)
185 inline long int gen_index() const {
186 return ((lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x;
190 * Generate the unique scenery tile index for this bucket in ascii
192 * @return tile index in string form
194 inline std::string gen_index_str() const {
196 std::sprintf(tmp, "%ld",
197 (((long)lon + 180) << 14) + ((lat + 90) << 6)
199 return (std::string)tmp;
203 * Build the base path name for this bucket.
204 * @return base path in string form
206 std::string gen_base_path() const;
209 * @return the center lon of a tile.
211 inline double get_center_lon() const {
212 double span = sg_bucket_span( lat + y / 8.0 + SG_HALF_BUCKET_SPAN );
215 return lon + get_width() / 2.0;
217 return lon + x * span + get_width() / 2.0;
222 * @return the center lat of a tile.
224 inline double get_center_lat() const {
225 return lat + y / 8.0 + SG_HALF_BUCKET_SPAN;
229 * @return the width of the tile in degrees.
231 double get_width() const;
234 * @return the height of the tile in degrees.
236 double get_height() const;
239 * @return the width of the tile in meters.
241 double get_width_m() const;
244 * @return the height of the tile in meters.
246 double get_height_m() const;
249 * @return the center of the bucket in geodetic coordinates.
251 SGGeod get_center() const
252 { return SGGeod::fromDeg(get_center_lon(), get_center_lat()); }
255 * @return the center of the bucket in geodetic coordinates.
257 SGGeod get_corner(unsigned num) const
259 double lonFac = ((num + 1) & 2) ? 0.5 : -0.5;
260 double latFac = ((num ) & 2) ? 0.5 : -0.5;
261 return SGGeod::fromDeg(get_center_lon() + lonFac*get_width(),
262 get_center_lat() + latFac*get_height());
265 // Informational methods.
268 * @return the lon of the lower left corner of
269 * the 1x1 chunk containing this tile.
271 inline int get_chunk_lon() const { return lon; }
274 * @return the lat of the lower left corner of
275 * the 1x1 chunk containing this tile.
277 inline int get_chunk_lat() const { return lat; }
280 * @return the x coord within the 1x1 degree chunk this tile.
282 inline int get_x() const { return x; }
285 * @return the y coord within the 1x1 degree chunk this tile.
287 inline int get_y() const { return y; }
291 friend std::ostream& operator<< ( std::ostream&, const SGBucket& );
292 friend bool operator== ( const SGBucket&, const SGBucket& );
295 inline bool operator!= (const SGBucket& lhs, const SGBucket& rhs)
297 return !(lhs == rhs);
303 * Return the bucket which is offset from the specified dlon, dlat by
304 * the specified tile units in the X & Y direction.
305 * @param dlon starting lon in degrees
306 * @param dlat starting lat in degrees
307 * @param x number of bucket units to offset in x (lon) direction
308 * @param y number of bucket units to offset in y (lat) direction
309 * @return offset bucket
311 SGBucket sgBucketOffset( double dlon, double dlat, int x, int y );
316 * Calculate the offset between two buckets (in quantity of buckets).
319 * @param dx offset distance (lon) in tile units
320 * @param dy offset distance (lat) in tile units
322 void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy );
326 * Write the bucket lon, lat, x, and y to the output stream.
327 * @param out output stream
331 operator<< ( std::ostream& out, const SGBucket& b )
333 return out << b.lon << ":" << (int)b.x << ", " << b.lat << ":" << (int)b.y;
338 * Compare two bucket structures for equality.
341 * @return comparison result
344 operator== ( const SGBucket& b1, const SGBucket& b2 )
346 return ( b1.lon == b2.lon &&
353 #endif // _NEWBUCKET_HXX