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flightgear/Bucket/bucketutils.c

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/**************************************************************************
* bucketutils.c -- support routines to handle fgBUCKET operations
*
* Written by Curtis Olson, started January 1998.
*
* 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)
**************************************************************************/
#include <math.h>
#include <stdio.h>
#include <Include/fg_constants.h>
#include "bucketutils.h"
/* Generate the unique scenery tile 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 tile 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) */
long int fgBucketGenIndex(struct fgBUCKET *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 tile index and find the lon, lat, x, and y */
void fgBucketParseIndex(long int index, struct fgBUCKET *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 tile index */
void fgBucketGenBasePath(struct fgBUCKET *p, char *path) {
long int index;
int top_lon, top_lat, main_lon, main_lat;
char hem, pole;
index = fgBucketGenIndex(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;
}
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;
}
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",
hem, top_lon, pole, top_lat,
hem, main_lon, pole, main_lat);
}
/* offset an bucket struct by the specified amounts in the X & Y direction */
void fgBucketOffset(struct fgBUCKET *in, struct fgBUCKET *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, find the "bucket" or tile that it falls within */
void fgBucketFind(double lon, double lat, struct fgBUCKET *p) {
double diff;
diff = lon - (double)(int)lon;
/* printf("diff = %.2f\n", diff); */
if ( (lon >= 0) || (fabs(diff) < FG_EPSILON) ) {
p->lon = (int)lon;
} else {
p->lon = (int)lon - 1;
}
/* printf(" p->lon = %d\n", p->lon); */
diff = lat - (double)(int)lat;
/* printf("diff = %.2f\n", diff); */
if ( (lat >= 0) || (fabs(diff) < FG_EPSILON) ) {
p->lat = (int)lat;
} else {
p->lat = (int)lat - 1;
}
/* printf(" p->lat = %d\n", p->lat); */
p->x = (int)((lon - p->lon) * 8);
p->y = (int)((lat - p->lat) * 8);
/* printf( "Bucket = lon,lat = %d,%d x,y index = %d,%d\n",
p->lon, p->lat, p->x, p->y); */
}
/* Given a lat/lon, fill in the local tile index array */
void fgBucketGenIdxArray(struct fgBUCKET *p1, struct fgBUCKET *tiles,
int width, int height) {
struct fgBUCKET *p2;
int dw, dh, i, j;
dh = height / 2;
dw = width / 2;
for ( j = 0; j < height; j++ ) {
for ( i = 0; i < width; i++ ) {
fgBucketOffset(p1, &tiles[(j*width)+i], i - dw, j - dh);
p2 = &tiles[(j*width)+i];
/* printf( " bucket = %d %d %d %d index = %ld\n",
p2->lon, p2->lat, p2->x, p2->y,
fgBucketGenIndex(&tiles[(j*width)+i])); */
}
}
}
/* sample main for testing
int main() {
struct fgBUCKET p1;
long int tile[49];
char path[256];
double lon, lat;
int i, j;
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;
find_bucket(lon, lat, &p1);
gen_idx_array(&p1, tile, 7, 7);
for ( j = 0; j < 7; j++ ) {
for ( i = 0; i < 7; i++ ) {
gen_path(tile[(j*7)+i], path);
printf(" path = %s\n", path);
}
}
lon = 50.0;
lat = 50.0;
find_bucket(lon, lat, &p1);
gen_idx_array(&p1, tile, 7, 7);
for ( j = 0; j < 7; j++ ) {
for ( i = 0; i < 7; i++ ) {
gen_path(tile[(j*7)+i], path);
printf(" path = %s\n", path);
}
}
return(1);
} */
/* $Log$
/* Revision 1.2 1998/04/25 22:06:22 curt
/* Edited cvs log messages in source files ... bad bad bad!
/*
* Revision 1.1 1998/04/08 23:28:58 curt
* Adopted Gnu automake/autoconf system.
*
* Revision 1.6 1998/02/09 15:07:51 curt
* Minor tweaks.
*
* Revision 1.5 1998/01/29 00:51:38 curt
* First pass at tile cache, dynamic tile loading and tile unloading now works.
*
* Revision 1.4 1998/01/27 03:26:41 curt
* Playing with new fgPrintf command.
*
* Revision 1.3 1998/01/27 00:48:01 curt
* Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
* system and commandline/config file processing code.
*
* Revision 1.2 1998/01/24 00:03:28 curt
* Initial revision.
*
* Revision 1.1 1998/01/23 20:06:51 curt
* tileutils.* renamed to bucketutils.*
*
* Revision 1.6 1998/01/19 19:27:18 curt
* Merged in make system changes from Bob Kuehne <rpk@sgi.com>
* This should simplify things tremendously.
*
* Revision 1.5 1998/01/14 02:19:04 curt
* Makde offset_bucket visible to outside.
*
* Revision 1.4 1998/01/13 00:23:12 curt
* Initial changes to support loading and management of scenery tiles. Note,
* there's still a fair amount of work left to be done.
*
* Revision 1.3 1998/01/10 00:01:47 curt
* Misc api changes and tweaks.
*
* Revision 1.2 1998/01/08 02:22:28 curt
* Continue working on basic features.
*
* Revision 1.1 1998/01/07 23:50:52 curt
* "area" renamed to "tile"
*
* Revision 1.1 1998/01/07 23:23:40 curt
* Initial revision.
*
* */
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