294 lines
7.2 KiB
C
294 lines
7.2 KiB
C
/**************************************************************************
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* tileutils.c -- support routines to handle dynamic management of scenery tiles
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*
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* Written by Curtis Olson, started January 1998.
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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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#include <math.h>
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#include <stdio.h>
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#include <Scenery/tileutils.h>
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#include <Include/constants.h>
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/* Generate the unique scenery tile 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 tile 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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long int gen_index(struct bucket *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 tile index and find the lon, lat, x, and y */
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void parse_index(long int index, struct bucket *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 tile index */
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void gen_base_path(struct bucket *p, char *path) {
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long int index;
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int top_lon, top_lat, main_lon, main_lat;
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char hem, pole;
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index = gen_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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}
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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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}
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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",
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hem, top_lon, pole, top_lat,
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hem, main_lon, pole, main_lat);
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}
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/* offset an bucket struct by the specified amounts in the X & Y direction */
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void offset_bucket(struct bucket *in, struct bucket *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, find the "bucket" or tile that it falls within */
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void find_bucket(double lon, double lat, struct bucket *p) {
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double diff;
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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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p->lon = (int)lon;
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} else {
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p->lon = (int)lon - 1;
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}
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/* printf(" p->lon = %d\n", p->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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p->lat = (int)lat;
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} else {
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p->lat = (int)lat - 1;
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}
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/* printf(" p->lat = %d\n", p->lat); */
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p->x = (lon - p->lon) * 8;
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p->y = (lat - p->lat) * 8;
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printf("Bucket = lon,lat = %d,%d x,y index = %d,%d\n",
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p->lon, p->lat, p->x, p->y);
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}
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/* Given a lat/lon, fill in the local tile index array */
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void gen_idx_array(struct bucket *p1, struct bucket *tiles,
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int width, int height) {
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struct bucket *p2;
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int dw, dh, i, j;
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dh = height / 2;
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dw = width / 2;
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for ( j = 0; j < height; j++ ) {
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for ( i = 0; i < width; i++ ) {
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offset_bucket(p1, &tiles[(j*width)+i], i - dw, j - dh);
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p2 = &tiles[(j*width)+i];
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printf(" bucket = %d %d %d %d index = %ld\n",
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p2->lon, p2->lat, p2->x, p2->y,
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gen_index(&tiles[(j*width)+i]));
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}
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}
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}
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/* sample main for testing
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int main() {
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struct bucket p1;
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long int tile[49];
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char path[256];
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double lon, lat;
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int i, j;
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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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find_bucket(lon, lat, &p1);
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gen_idx_array(&p1, tile, 7, 7);
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for ( j = 0; j < 7; j++ ) {
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for ( i = 0; i < 7; i++ ) {
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gen_path(tile[(j*7)+i], path);
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printf(" path = %s\n", path);
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}
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}
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lon = 50.0;
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lat = 50.0;
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find_bucket(lon, lat, &p1);
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gen_idx_array(&p1, tile, 7, 7);
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for ( j = 0; j < 7; j++ ) {
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for ( i = 0; i < 7; i++ ) {
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gen_path(tile[(j*7)+i], path);
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printf(" path = %s\n", path);
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}
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}
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return(1);
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} */
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/* $Log$
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/* Revision 1.6 1998/01/19 19:27:18 curt
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/* Merged in make system changes from Bob Kuehne <rpk@sgi.com>
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/* This should simplify things tremendously.
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/*
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* Revision 1.5 1998/01/14 02:19:04 curt
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* Makde offset_bucket visible to outside.
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*
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* Revision 1.4 1998/01/13 00:23:12 curt
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* Initial changes to support loading and management of scenery tiles. Note,
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* there's still a fair amount of work left to be done.
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*
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* Revision 1.3 1998/01/10 00:01:47 curt
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* Misc api changes and tweaks.
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*
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* Revision 1.2 1998/01/08 02:22:28 curt
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* Continue working on basic features.
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*
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* Revision 1.1 1998/01/07 23:50:52 curt
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* "area" renamed to "tile"
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*
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* Revision 1.1 1998/01/07 23:23:40 curt
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* Initial revision.
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*
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* */
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