flightgear/Scenery/tilecache.c

/**************************************************************************
 * tilecache.c -- routines to handle scenery tile caching
 *
 * 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)
 **************************************************************************/


#ifdef WIN32
#  include <windows.h>
#endif

#include <GL/glut.h>
#include <XGL/xgl.h>

#include <Include/general.h>
#include <Main/fg_debug.h>
#include <Main/views.h>
#include <Scenery/bucketutils.h>
#include <Scenery/obj.h>
#include <Scenery/tilecache.h>


/* tile cache */
struct fgTILE tile_cache[FG_TILE_CACHE_SIZE];


/* Initialize the tile cache subsystem */
void fgTileCacheInit( void ) {
    int i;

    fgPrintf(FG_TERRAIN, FG_INFO, "Initializing the tile cache.\n");

    for ( i = 0; i < FG_TILE_CACHE_SIZE; i++ ) {
	tile_cache[i].used = 0;
    }
}


/* Search for the specified "bucket" in the cache */
int fgTileCacheExists( struct fgBUCKET *p ) {
    int i;

    for ( i = 0; i < FG_TILE_CACHE_SIZE; i++ ) {
	if ( tile_cache[i].tile_bucket.lon == p->lon ) {
	    if ( tile_cache[i].tile_bucket.lat == p->lat ) {
		if ( tile_cache[i].tile_bucket.x == p->x ) {
		    if ( tile_cache[i].tile_bucket.y == p->y ) {
			fgPrintf( FG_TERRAIN, FG_DEBUG, 
				  "TILE EXISTS in cache ... index = %d\n", i );
			return( i );
		    }
		}
	    }
	}
    }
    
    return( -1 );
}


/* Fill in a tile cache entry with real data for the specified bucket */
void fgTileCacheEntryFillIn( int index, struct fgBUCKET *p ) {
    struct fgGENERAL *g;
    char base_path[256];
    char file_name[256];

    g = &general;

    /* Mark this cache entry as used */
    tile_cache[index].used = 1;

    /* Update the bucket */
    tile_cache[index].tile_bucket.lon = p->lon;
    tile_cache[index].tile_bucket.lat = p->lat;
    tile_cache[index].tile_bucket.x = p->x;
    tile_cache[index].tile_bucket.y = p->y;

    /* Load the appropriate area and get the display list pointer */
    fgBucketGenBasePath(p, base_path);
    sprintf(file_name, "%s/Scenery/%s/%ld.obj", g->root_dir, 
	    base_path, fgBucketGenIndex(p));
    tile_cache[index].display_list = 
	fgObjLoad(file_name, &tile_cache[index].local_ref,
		  &tile_cache[index].bounding_radius);    
}


/* Free a tile cache entry */
void fgTileCacheEntryFree( int index ) {
    /* Mark this cache entry as un-used */
    tile_cache[index].used = 0;

    /* Update the bucket */
    fgPrintf( FG_TERRAIN, FG_DEBUG, 
	      "FREEING TILE = (%d %d %d %d)\n",
	      tile_cache[index].tile_bucket.lon, 
	      tile_cache[index].tile_bucket.lat, 
	      tile_cache[index].tile_bucket.x,
	      tile_cache[index].tile_bucket.y );

    /* Load the appropriate area and get the display list pointer */
    if ( tile_cache[index].display_list >= 0 ) {
	xglDeleteLists( tile_cache[index].display_list, 1 );
    }
}


/* Return info for a tile cache entry */
void fgTileCacheEntryInfo( int index, GLint *display_list, 
			   struct fgCartesianPoint *local_ref ) {
    *display_list = tile_cache[index].display_list;
    /* fgPrintf(FG_TERRAIN, FG_DEBUG, "Display list = %d\n", *display_list); */

    local_ref->x = tile_cache[index].local_ref.x;
    local_ref->y = tile_cache[index].local_ref.y;
    local_ref->z = tile_cache[index].local_ref.z;
}


/* Return index of next available slot in tile cache */
int fgTileCacheNextAvail( void ) {
    struct fgVIEW *v;
    int i;
    float dx, dy, dz, max, med, min, tmp;
    float dist, max_dist;
    int max_index;
    
    v = &current_view;

    max_dist = 0.0;
    max_index = 0;

    for ( i = 0; i < FG_TILE_CACHE_SIZE; i++ ) {
	if ( tile_cache[i].used == 0 ) {
	    return(i);
	} else {
	    /* calculate approximate distance from view point */
	    fgPrintf( FG_TERRAIN, FG_DEBUG,
		      "DIST Abs view pos = %.4f, %.4f, %.4f\n", 
		      v->abs_view_pos.x, v->abs_view_pos.y, v->abs_view_pos.z );
	    fgPrintf( FG_TERRAIN, FG_DEBUG,
		      "    ref point = %.4f, %.4f, %.4f\n", 
		      tile_cache[i].local_ref.x, tile_cache[i].local_ref.y,
		      tile_cache[i].local_ref.z);

	    dx = fabs(tile_cache[i].local_ref.x - v->abs_view_pos.x);
	    dy = fabs(tile_cache[i].local_ref.y - v->abs_view_pos.y);
	    dz = fabs(tile_cache[i].local_ref.z - v->abs_view_pos.z);

	    max = dx; med = dy; min = dz;
	    if ( max < med ) {
		tmp = max; max = med; med = tmp;
	    }
	    if ( max < min ) {
		tmp = max; max = min; min = tmp;
	    }
	    dist = max + (med + min) / 4;

	    fgPrintf( FG_TERRAIN, FG_DEBUG, "    distance = %.2f\n", dist);

	    if ( dist > max_dist ) {
		max_dist = dist;
		max_index = i;
	    }
	}
    }

    /* If we made it this far, then there were no open cache entries.
     * We will instead free the furthest cache entry and return it's
     * index. */
    
    fgTileCacheEntryFree( max_index );
    return( max_index );
}


/* $Log$
/* Revision 1.7  1998/02/01 03:39:55  curt
/* Minor tweaks.
/*
 * Revision 1.6  1998/01/31 00:43:26  curt
 * Added MetroWorks patches from Carmen Volpe.
 *
 * Revision 1.5  1998/01/29 00:51:39  curt
 * First pass at tile cache, dynamic tile loading and tile unloading now works.
 *
 * Revision 1.4  1998/01/27 03:26:43  curt
 * Playing with new fgPrintf command.
 *
 * Revision 1.3  1998/01/27 00:48:03  curt
 * Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
 * system and commandline/config file processing code.
 *
 * Revision 1.2  1998/01/26 15:55:24  curt
 * Progressing on building dynamic scenery system.
 *
 * Revision 1.1  1998/01/24 00:03:29  curt
 * Initial revision.
 *
 */