/************************************************************************** * areamgr.c -- routines to handle dynamic management of scenery areas * * Written by Curtis Olson, started October 1997. * * Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id$ * (Log is kept at end of this file) **************************************************************************/ #ifdef WIN32 # include #endif #include #include "../XGL/xgl.h" #include #include "../Include/constants.h" /* temporary */ #include "../Math/fg_random.h" struct ai { int lon; /* longitude (-180 to 179) */ int lat; /* latitude (-90 to 89) */ int x; /* x (0 to 7) */ int y; /* y (0 to 7) */ }; /* we're entering into hacking territory here ... what fun. ;-) */ long int area_array[7][7]; /* Generate the unique scenery area index containing the specified lon/lat parameters. The index is constructed as follows: 9 bits - to represent 360 degrees of longitude (-180 to 179) 8 bits - to represent 180 degrees of latitude (-90 to 89) Each 1 degree by 1 degree area is further broken down into an 8x8 grid. So we also need: 3 bits - to represent x (0 to 7) 3 bits - to represent y (0 to 7) */ static long gen_index(struct ai *p) { long index = 0; index = ((p->lon + 180) << 14) + ((p->lat + 90) << 6) + (p->y << 3) + p->x; /* printf(" generated index = %ld\n", index); */ return(index); } /* Parse a unique scenery area index and find the lon, lat, x, and y */ static void parse_index(long int index, struct ai *p) { p->lon = index >> 14; index -= p->lon << 14; p->lon -= 180; p->lat = index >> 6; index -= p->lat << 6; p->lat -= 90; p->y = index >> 3; index -= p->y << 3; p->x = index; } /* Build a path name from an area index */ static void gen_path(long int index, char *path) { struct ai p; int top_lon, top_lat, main_lon, main_lat; char hem, pole; parse_index(index, &p); path[0] = '\0'; top_lon = p.lon / 10; main_lon = p.lon; if ( (p.lon < 0) && (top_lon * 10 != p.lon) ) { top_lon -= 1; main_lon -= 1; } top_lon *= 10; if ( top_lon >= 0 ) { hem = 'e'; } else { hem = 'w'; top_lon *= -1; } if ( main_lon < 0 ) { main_lon *= -1; } top_lat = p.lat / 10; main_lat = p.lat; if ( (p.lat < 0) && (top_lat * 10 != p.lat) ) { top_lat -= 1; main_lat -= 1; } top_lat *= 10; if ( top_lat >= 0 ) { pole = 'n'; } else { pole = 's'; top_lat *= -1; } if ( main_lat < 0 ) { main_lat *= -1; } sprintf(path, "%c%03d%c%03d/%c%03d%c%03d/%ld.ter", hem, top_lon, pole, top_lat, hem, main_lon, pole, main_lat, index); } /* offset an ai struct by the specified amounts in the X & Y direction */ static void offset_ai(struct ai *in, struct ai *out, int x, int y) { int diff, temp; int dist_lat; out->lon = in->lon; out->lat = in->lat; out->x = in->x; out->y = in->y; /* do X direction */ diff = out->x + x; /* printf(" reducing x (%d)\n", diff); */ if ( diff >= 0 ) { temp = diff / 8; } else if ( diff < -7 ) { temp = (diff + 1) / 8 - 1; } else { temp = diff / 8 - 1; } out->x = ((diff % 8) + 8) % 8; out->lon = ( (out->lon + 180 + 360 + temp) % 360 ) - 180; /* do Y direction */ diff = out->y + y; /* printf(" reducing x (%d)\n", diff); */ if ( diff >= 0 ) { temp = diff / 8; } else if ( diff < -7 ) { temp = (diff + 1) / 8 - 1; } else { temp = diff / 8 - 1; } out->y = ((diff % 8) + 8) % 8; out->lat = out->lat + temp; if ( out->lat >= 90 ) { dist_lat = out->lat - 90; /* printf(" +lat = %d +y = %d\n", dist_lat, out->y); */ out->lat = 90 - (dist_lat + 1); out->lon = ( (out->lon + 180 + 180) % 360 ) - 180; out->y = 7 - out->y; } if ( out->lat < -90 ) { dist_lat = -90 - out->lat; /* printf(" +lat = %d +y = %d\n", dist_lat, out->y); */ out->lat = -90 + (dist_lat - 1); out->lon = ( (out->lon + 180 + 180) % 360 ) - 180; out->y = 7 - out->y; } } /* Given a lat/lon, fill in the local area index array */ static void gen_idx_array(double lon, double lat) { struct ai p1, p2, p3; double diff; char path[256]; long int index = 0; int i, j; printf("lon = %.2f lat = %.2f\n", lon, lat); diff = lon - (double)(int)lon; printf("diff = %.2f\n", diff); if ( (lon >= 0) || (fabs(diff) < FG_EPSILON) ) { p1.lon = (int)lon; } else { p1.lon = (int)lon - 1; } printf(" p1.lon = %d\n", p1.lon); diff = lat - (double)(int)lat; printf("diff = %.2f\n", diff); if ( (lat >= 0) || (fabs(diff) < FG_EPSILON) ) { p1.lat = (int)lat; } else { p1.lat = (int)lat - 1; } printf(" p1.lat = %d\n", p1.lat); p1.x = (lon - p1.lon) * 8; p1.y = (lat - p1.lat) * 8; printf(" lon,lat = %d,%d x,y index = %d,%d\n", p1.lon, p1.lat, p1.x, p1.y); for ( i = -3; i <= 3; i++ ) { for ( j = -3; j <= 3; j++ ) { offset_ai(&p1, &p2, i, j); printf(" %d %d %d %d\n", p2.lon, p2.lat, p2.x, p2.y); area_array[i][j] = gen_index(&p2); printf(" generated index = %ld\n", area_array[i][j]); /* parse_index(area_array[i][j], &p3); */ /* printf(" %d %d %d %d\n", p3.lon, p3.lat, p3.x, p3.y); */ gen_path(area_array[i][j], path); printf(" path = %s\n\n", path); } } } main() { struct ai p1; int i, j, index; double lon, lat; fg_srandom(); p1.lon = 180; p1.lat = 90; p1.x = 7; p1.y = 7; /* printf("Max index = %ld\n", gen_index(&p1)); */ lon = -50.0; lat = -50.0; gen_idx_array(lon, lat); lon = 50.0; lat = 50.0; gen_idx_array(lon, lat); for ( i = 0; i < 100; i++ ) { lon = ( 360.0 * fg_random() ) - 180.0; lat = ( 180.0 * fg_random() ) - 90.0; gen_idx_array(lon, lat); } } /* $Log$ /* Revision 1.2 1998/01/07 03:29:29 curt /* Given an arbitrary lat/lon, we can now: /* generate a unique index for the chunk containing the lat/lon /* generate a path name to the chunk file /* build a list of the indexes of all the nearby areas. /* * Revision 1.1 1998/01/07 02:05:48 curt * Initial revision. * */