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.
29 #ifndef _NEWBUCKET_HXX
30 #define _NEWBUCKET_HXX
32 #include <simgear/compiler.h>
33 #include <simgear/constants.h>
34 #include <simgear/math/SGMath.hxx>
36 #ifdef SG_HAVE_STD_INCLUDES
38 # include <cstdio> // sprintf()
41 # include <stdio.h> // sprintf()
46 // I don't understand ... <math.h> or <cmath> should be included
47 // already depending on how you defined SG_HAVE_STD_INCLUDES, but I
48 // can go ahead and add this -- CLO
50 SG_USING_STD(sprintf);
57 SG_USING_STD(ostream);
61 * standard size of a bucket in degrees (1/8 of a degree)
63 #define SG_BUCKET_SPAN 0.125
66 * half of a standard SG_BUCKET_SPAN
68 #define SG_HALF_BUCKET_SPAN ( 0.5 * SG_BUCKET_SPAN )
71 // return the horizontal tile span factor based on latitude
72 static double sg_bucket_span( double l ) {
75 } else if ( l >= 88.0 ) {
77 } else if ( l >= 86.0 ) {
79 } else if ( l >= 83.0 ) {
81 } else if ( l >= 76.0 ) {
83 } else if ( l >= 62.0 ) {
85 } else if ( l >= 22.0 ) {
87 } else if ( l >= -22.0 ) {
89 } else if ( l >= -62.0 ) {
91 } else if ( l >= -76.0 ) {
93 } else if ( l >= -83.0 ) {
95 } else if ( l >= -86.0 ) {
97 } else if ( l >= -88.0 ) {
99 } else if ( l >= -89.0 ) {
108 * A class to manage world scenery tiling.
109 * This class encapsulates the world tiling scheme. It provides ways
110 * to calculate a unique tile index from a lat/lon, and it can provide
111 * information such as the dimensions of a given tile.
117 double cx, cy; // centerpoint (lon, lat) in degrees of bucket
118 short lon; // longitude index (-180 to 179)
119 short lat; // latitude index (-90 to 89)
120 char x; // x subdivision (0 to 7)
121 char y; // y subdivision (0 to 7)
126 * Default constructor.
131 * Construct a bucket given a specific location.
132 * @param dlon longitude specified in degrees
133 * @param dlat latitude specified in degrees
135 SGBucket(const double dlon, const double dlat);
137 /** Construct a bucket.
138 * @param is_good if false, create an invalid bucket. This is
139 * useful * if you are comparing cur_bucket to last_bucket and
140 * you want to * make sure last_bucket starts out as something
143 SGBucket(const bool is_good);
145 /** Construct a bucket given a unique bucket index number.
146 * @param bindex unique bucket index
148 SGBucket(const long int bindex);
151 * Default destructor.
156 * Reset a bucket to represent a new lat and lon
157 * @param dlon longitude specified in degrees
158 * @param dlat latitude specified in degrees
160 void set_bucket( double dlon, double dlat );
163 * Reset a bucket to represent a new lat and lon
164 * @param lonlat an array of double[2] holding lon and lat
165 * (specified) in degrees
167 void set_bucket( double *lonlat );
170 * Create an impossible bucket.
171 * This is useful if you are comparing cur_bucket to last_bucket
172 * and you want to make sure last_bucket starts out as something
175 inline void make_bad() {
176 set_bucket(0.0, 0.0);
181 * Generate the unique scenery tile index for this bucket
183 * The index is constructed as follows:
185 * 9 bits - to represent 360 degrees of longitude (-180 to 179)
186 * 8 bits - to represent 180 degrees of latitude (-90 to 89)
188 * Each 1 degree by 1 degree tile is further broken down into an 8x8
189 * grid. So we also need:
191 * 3 bits - to represent x (0 to 7)
192 * 3 bits - to represent y (0 to 7)
195 inline long int gen_index() const {
196 return ((lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x;
200 * Generate the unique scenery tile index for this bucket in ascii
202 * @return tile index in string form
204 inline string gen_index_str() const {
207 (((long)lon + 180) << 14) + ((lat + 90) << 6) + (y << 3) + x);
212 * Build the base path name for this bucket.
213 * @return base path in string form
215 string gen_base_path() const;
218 * @return the center lon of a tile.
220 inline double get_center_lon() const {
221 double span = sg_bucket_span( lat + y / 8.0 + SG_HALF_BUCKET_SPAN );
224 return lon + span / 2.0;
226 return lon + x * span + span / 2.0;
231 * @return the center lat of a tile.
233 inline double get_center_lat() const {
234 return lat + y / 8.0 + SG_HALF_BUCKET_SPAN;
238 * @return the width of the tile in degrees.
240 double get_width() const;
243 * @return the height of the tile in degrees.
245 double get_height() const;
248 * @return the width of the tile in meters.
250 double get_width_m() const;
253 * @return the height of the tile in meters.
255 double get_height_m() const;
258 * @return the center of the bucket in geodetic coordinates.
260 SGGeod get_center() const
261 { return SGGeod::fromDeg(get_center_lon(), get_center_lat()); }
264 * @return the center of the bucket in geodetic coordinates.
266 SGGeod get_corner(unsigned num) const
268 double lonFac = ((num + 1) & 2) ? 0.5 : -0.5;
269 double latFac = ((num ) & 2) ? 0.5 : -0.5;
270 return SGGeod::fromDeg(get_center_lon() + lonFac*get_width(),
271 get_center_lat() + latFac*get_height());
274 // Informational methods.
277 * @return the lon of the lower left corner of
278 * the 1x1 chunk containing this tile.
280 inline int get_chunk_lon() const { return lon; }
283 * @return the lat of the lower left corner of
284 * the 1x1 chunk containing this tile.
286 inline int get_chunk_lat() const { return lat; }
289 * @return the x coord within the 1x1 degree chunk this tile.
291 inline int get_x() const { return x; }
294 * @return the y coord within the 1x1 degree chunk this tile.
296 inline int get_y() const { return y; }
300 friend ostream& operator<< ( ostream&, const SGBucket& );
301 friend bool operator== ( const SGBucket&, const SGBucket& );
307 * Return the bucket which is offset from the specified dlon, dlat by
308 * the specified tile units in the X & Y direction.
309 * @param dlon starting lon in degrees
310 * @param dlat starting lat in degrees
311 * @param x number of bucket units to offset in x (lon) direction
312 * @param y number of bucket units to offset in y (lat) direction
313 * @return offset bucket
315 SGBucket sgBucketOffset( double dlon, double dlat, int x, int y );
320 * Calculate the offset between two buckets (in quantity of buckets).
323 * @param dx offset distance (lon) in tile units
324 * @param dy offset distance (lat) in tile units
326 void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy );
330 * Write the bucket lon, lat, x, and y to the output stream.
331 * @param out output stream
335 operator<< ( ostream& out, const SGBucket& b )
337 return out << b.lon << ":" << b.x << ", " << b.lat << ":" << b.y;
342 * Compare two bucket structures for equality.
345 * @return comparison result
348 operator== ( const SGBucket& b1, const SGBucket& b2 )
350 return ( b1.lon == b2.lon &&
357 #endif // _NEWBUCKET_HXX