ecd729cf47
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.
291 lines
6.9 KiB
C
291 lines
6.9 KiB
C
/**************************************************************************
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* areamgr.c -- routines to handle dynamic management of scenery areas
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*
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* Written by Curtis Olson, started October 1997.
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*
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* Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#ifdef WIN32
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# include <windows.h>
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#endif
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#include <GL/glut.h>
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#include "../XGL/xgl.h"
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#include <math.h>
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#include "../Include/constants.h"
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/* temporary */
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#include "../Math/fg_random.h"
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struct ai {
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int lon; /* longitude (-180 to 179) */
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int lat; /* latitude (-90 to 89) */
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int x; /* x (0 to 7) */
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int y; /* y (0 to 7) */
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};
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/* we're entering into hacking territory here ... what fun. ;-) */
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long int area_array[7][7];
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/* Generate the unique scenery area index containing the specified
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lon/lat parameters.
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The index is constructed as follows:
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9 bits - to represent 360 degrees of longitude (-180 to 179)
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8 bits - to represent 180 degrees of latitude (-90 to 89)
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Each 1 degree by 1 degree area is further broken down into an 8x8
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grid. So we also need:
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3 bits - to represent x (0 to 7)
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3 bits - to represent y (0 to 7) */
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static long gen_index(struct ai *p) {
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long index = 0;
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index = ((p->lon + 180) << 14) + ((p->lat + 90) << 6) + (p->y << 3) + p->x;
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/* printf(" generated index = %ld\n", index); */
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return(index);
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}
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/* Parse a unique scenery area index and find the lon, lat, x, and y */
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static void parse_index(long int index, struct ai *p) {
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p->lon = index >> 14;
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index -= p->lon << 14;
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p->lon -= 180;
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p->lat = index >> 6;
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index -= p->lat << 6;
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p->lat -= 90;
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p->y = index >> 3;
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index -= p->y << 3;
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p->x = index;
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}
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/* Build a path name from an area index */
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static void gen_path(long int index, char *path) {
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struct ai p;
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int top_lon, top_lat, main_lon, main_lat;
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char hem, pole;
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parse_index(index, &p);
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path[0] = '\0';
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top_lon = p.lon / 10;
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main_lon = p.lon;
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if ( (p.lon < 0) && (top_lon * 10 != p.lon) ) {
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top_lon -= 1;
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main_lon -= 1;
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}
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top_lon *= 10;
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if ( top_lon >= 0 ) {
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hem = 'e';
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} else {
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hem = 'w';
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top_lon *= -1;
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}
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if ( main_lon < 0 ) {
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main_lon *= -1;
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}
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top_lat = p.lat / 10;
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main_lat = p.lat;
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if ( (p.lat < 0) && (top_lat * 10 != p.lat) ) {
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top_lat -= 1;
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main_lat -= 1;
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}
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top_lat *= 10;
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if ( top_lat >= 0 ) {
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pole = 'n';
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} else {
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pole = 's';
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top_lat *= -1;
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}
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if ( main_lat < 0 ) {
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main_lat *= -1;
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}
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sprintf(path, "%c%03d%c%03d/%c%03d%c%03d/%ld.ter",
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hem, top_lon, pole, top_lat,
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hem, main_lon, pole, main_lat,
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index);
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}
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/* offset an ai struct by the specified amounts in the X & Y direction */
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static void offset_ai(struct ai *in, struct ai *out, int x, int y) {
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int diff, temp;
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int dist_lat;
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out->lon = in->lon;
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out->lat = in->lat;
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out->x = in->x;
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out->y = in->y;
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/* do X direction */
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diff = out->x + x;
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/* printf(" reducing x (%d)\n", diff); */
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if ( diff >= 0 ) {
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temp = diff / 8;
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} else if ( diff < -7 ) {
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temp = (diff + 1) / 8 - 1;
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} else {
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temp = diff / 8 - 1;
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}
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out->x = ((diff % 8) + 8) % 8;
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out->lon = ( (out->lon + 180 + 360 + temp) % 360 ) - 180;
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/* do Y direction */
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diff = out->y + y;
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/* printf(" reducing x (%d)\n", diff); */
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if ( diff >= 0 ) {
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temp = diff / 8;
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} else if ( diff < -7 ) {
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temp = (diff + 1) / 8 - 1;
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} else {
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temp = diff / 8 - 1;
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}
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out->y = ((diff % 8) + 8) % 8;
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out->lat = out->lat + temp;
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if ( out->lat >= 90 ) {
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dist_lat = out->lat - 90;
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/* printf(" +lat = %d +y = %d\n", dist_lat, out->y); */
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out->lat = 90 - (dist_lat + 1);
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out->lon = ( (out->lon + 180 + 180) % 360 ) - 180;
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out->y = 7 - out->y;
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}
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if ( out->lat < -90 ) {
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dist_lat = -90 - out->lat;
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/* printf(" +lat = %d +y = %d\n", dist_lat, out->y); */
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out->lat = -90 + (dist_lat - 1);
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out->lon = ( (out->lon + 180 + 180) % 360 ) - 180;
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out->y = 7 - out->y;
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}
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}
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/* Given a lat/lon, fill in the local area index array */
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static void gen_idx_array(double lon, double lat) {
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struct ai p1, p2, p3;
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double diff;
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char path[256];
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long int index = 0;
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int i, j;
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printf("lon = %.2f lat = %.2f\n", lon, lat);
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diff = lon - (double)(int)lon;
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printf("diff = %.2f\n", diff);
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if ( (lon >= 0) || (fabs(diff) < FG_EPSILON) ) {
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p1.lon = (int)lon;
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} else {
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p1.lon = (int)lon - 1;
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}
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printf(" p1.lon = %d\n", p1.lon);
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diff = lat - (double)(int)lat;
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printf("diff = %.2f\n", diff);
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if ( (lat >= 0) || (fabs(diff) < FG_EPSILON) ) {
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p1.lat = (int)lat;
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} else {
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p1.lat = (int)lat - 1;
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}
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printf(" p1.lat = %d\n", p1.lat);
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p1.x = (lon - p1.lon) * 8;
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p1.y = (lat - p1.lat) * 8;
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printf(" lon,lat = %d,%d x,y index = %d,%d\n",
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p1.lon, p1.lat, p1.x, p1.y);
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for ( i = -3; i <= 3; i++ ) {
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for ( j = -3; j <= 3; j++ ) {
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offset_ai(&p1, &p2, i, j);
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printf(" %d %d %d %d\n", p2.lon, p2.lat, p2.x, p2.y);
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area_array[i][j] = gen_index(&p2);
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printf(" generated index = %ld\n", area_array[i][j]);
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/* parse_index(area_array[i][j], &p3); */
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/* printf(" %d %d %d %d\n", p3.lon, p3.lat, p3.x, p3.y); */
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gen_path(area_array[i][j], path);
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printf(" path = %s\n\n", path);
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}
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}
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}
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main() {
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struct ai p1;
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int i, j, index;
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double lon, lat;
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fg_srandom();
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p1.lon = 180;
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p1.lat = 90;
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p1.x = 7;
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p1.y = 7;
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/* printf("Max index = %ld\n", gen_index(&p1)); */
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lon = -50.0;
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lat = -50.0;
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gen_idx_array(lon, lat);
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lon = 50.0;
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lat = 50.0;
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gen_idx_array(lon, lat);
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for ( i = 0; i < 100; i++ ) {
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lon = ( 360.0 * fg_random() ) - 180.0;
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lat = ( 180.0 * fg_random() ) - 90.0;
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gen_idx_array(lon, lat);
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}
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}
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/* $Log$
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/* Revision 1.2 1998/01/07 03:29:29 curt
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/* Given an arbitrary lat/lon, we can now:
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/* generate a unique index for the chunk containing the lat/lon
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/* generate a path name to the chunk file
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/* build a list of the indexes of all the nearby areas.
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/*
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* Revision 1.1 1998/01/07 02:05:48 curt
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* Initial revision.
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* */
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