--- /dev/null
+/**************************************************************************
+ * 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 <windows.h>
+#endif
+
+#include <GL/glut.h>
+#include "../XGL/xgl.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(struct ai *p, char *path) {
+ int top_lon, top_lat, main_lon, main_lat;
+ char hem, pole;
+
+ path[0] = '\0';
+
+ top_lon = p->lon / 10;
+ main_lon = p->lon;
+ if ( p->lon < 0 ) {
+ top_lon -= 1;
+ top_lon *= -1;
+ main_lon -= 1;
+ main_lon *= -1;
+ hem = 'w';
+ } else {
+ hem = 'e';
+ }
+ top_lon *= 10;
+
+ top_lat = p->lat / 10;
+ main_lat = p->lat;
+ if ( p->lat < 0 ) {
+ top_lat -= 1;
+ top_lat *= -1;
+ main_lat -= 1;
+ main_lat *= -1;
+ pole = 's';
+ } else {
+ pole = 'n';
+ }
+ top_lat *= 10;
+
+ sprintf(path, "%c%03d%c%03d/%c%03d%c%03d/",
+ hem, top_lon, pole, top_lat,
+ hem, main_lon, pole, main_lat);
+}
+
+
+/* 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;
+ char path[256];
+ long int index = 0;
+ int i, j;
+
+ printf("lon = %.2f lat = %.2f\n", lon, lat);
+
+ if ( lon < 0 ) {
+ p1.lon = (int)lon - 1;
+ } else {
+ p1.lon = (int)lon;
+ }
+ printf(" p1.lon = %d\n", p1.lon);
+
+ if ( lat < 0 ) {
+ p1.lat = (int)lat - 1;
+ } else {
+ p1.lat = (int)lat;
+ }
+ printf(" p1.lat = %d\n", p1.lat);
+
+ p1.x = (lon - p1.lon) * 8;
+ p1.y = (lat - p1.lat) * 8;
+ printf(" x,y index = %d,%d\n", 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(&p3, path);
+ printf(" path = %s\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));
+
+ 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 1.1 1998/01/07 02:05:48 curt
+/* Initial revision.
+/* */
+
+
projects / flightgear.git / commitdiff