1
0
Fork 0
flightgear/Scenery/tilemgr.cxx
curt e33dbca814 Attempting to iron out seg faults and crashes.
Did some shuffling to fix a initialization order problem between view
position, scenery elevation.
1998-08-22 14:49:55 +00:00

903 lines
28 KiB
C++

// tilemgr.cxx -- routines to handle dynamic management of scenery tiles
//
// 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 HAVE_CONFIG_H
# include <config.h>
#endif
#ifdef HAVE_WINDOWS_H
# include <windows.h>
#endif
#include <GL/glut.h>
#include <XGL/xgl.h>
#include <Aircraft/aircraft.h>
#include <Bucket/bucketutils.h>
#include <Debug/fg_debug.h>
#include <Include/fg_constants.h>
#include <Include/fg_types.h>
#include <Main/options.hxx>
#include <Main/views.hxx>
#include <Math/fg_geodesy.h>
#include <Math/mat3.h>
#include <Math/polar3d.hxx>
#include <Math/vector.hxx>
#include <Weather/weather.h>
#include "material.hxx"
#include "obj.hxx"
#include "scenery.hxx"
#include "tilecache.hxx"
#define FG_LOCAL_X_Y 81 // max(o->tile_diameter) ** 2
#define FG_SQUARE( X ) ( (X) * (X) )
// closest (potentially viewable) tiles, centered on current tile.
// This is an array of pointers to cache indexes.
int tiles[FG_LOCAL_X_Y];
// Initialize the Tile Manager subsystem
int fgTileMgrInit( void ) {
fgPrintf( FG_TERRAIN, FG_INFO, "Initializing Tile Manager subsystem.\n");
// load default material library
material_mgr.load_lib();
return 1;
}
// load a tile
void fgTileMgrLoadTile( fgBUCKET *p, int *index) {
fgTILECACHE *c;
c = &global_tile_cache;
fgPrintf( FG_TERRAIN, FG_DEBUG, "Updating for bucket %d %d %d %d\n",
p->lon, p->lat, p->x, p->y);
// if not in cache, load tile into the next available slot
if ( (*index = c->Exists(p)) < 0 ) {
*index = c->NextAvail();
c->EntryFillIn(*index, p);
}
fgPrintf( FG_TERRAIN, FG_DEBUG, "Selected cache index of %d\n", *index);
}
// given the current lon/lat, fill in the array of local chunks. If
// the chunk isn't already in the cache, then read it from disk.
int fgTileMgrUpdate( void ) {
fgTILECACHE *c;
fgFLIGHT *f;
fgBUCKET p1, p2;
static fgBUCKET p_last = {-1000, 0, 0, 0};
int tile_diameter;
int i, j, dw, dh;
c = &global_tile_cache;
f = current_aircraft.flight;
tile_diameter = current_options.get_tile_diameter();
fgBucketFind(FG_Longitude * RAD_TO_DEG, FG_Latitude * RAD_TO_DEG, &p1);
dw = tile_diameter / 2;
dh = tile_diameter / 2;
if ( (p1.lon == p_last.lon) && (p1.lat == p_last.lat) &&
(p1.x == p_last.x) && (p1.y == p_last.y) ) {
// same bucket as last time
fgPrintf( FG_TERRAIN, FG_DEBUG, "Same bucket as last time\n");
} else if ( p_last.lon == -1000 ) {
// First time through, initialize the system and load all
// relavant tiles
fgPrintf( FG_TERRAIN, FG_INFO, " First time through ... ");
fgPrintf( FG_TERRAIN, FG_INFO, " Updating Tile list for %d,%d %d,%d\n",
p1.lon, p1.lat, p1.x, p1.y);
fgPrintf( FG_TERRAIN, FG_INFO, " Loading %d tiles\n",
tile_diameter * tile_diameter);
// wipe/initialize tile cache
c->Init();
// build the local area list and update cache
for ( j = 0; j < tile_diameter; j++ ) {
for ( i = 0; i < tile_diameter; i++ ) {
fgBucketOffset(&p1, &p2, i - dw, j - dh);
fgTileMgrLoadTile(&p2, &tiles[(j*tile_diameter) + i]);
}
}
} else {
// We've moved to a new bucket, we need to scroll our
// structures, and load in the new tiles
// CURRENTLY THIS ASSUMES WE CAN ONLY MOVE TO ADJACENT TILES.
// AT ULTRA HIGH SPEEDS THIS ASSUMPTION MAY NOT BE VALID IF
// THE AIRCRAFT CAN SKIP A TILE IN A SINGLE ITERATION.
fgPrintf( FG_TERRAIN, FG_INFO, "Updating Tile list for %d,%d %d,%d\n",
p1.lon, p1.lat, p1.x, p1.y);
if ( (p1.lon > p_last.lon) ||
( (p1.lon == p_last.lon) && (p1.x > p_last.x) ) ) {
fgPrintf( FG_TERRAIN, FG_INFO, " Loading %d tiles\n",
tile_diameter);
for ( j = 0; j < tile_diameter; j++ ) {
// scrolling East
for ( i = 0; i < tile_diameter - 1; i++ ) {
tiles[(j*tile_diameter) + i] =
tiles[(j*tile_diameter) + i + 1];
}
// load in new column
fgBucketOffset(&p_last, &p2, dw + 1, j - dh);
fgTileMgrLoadTile(&p2, &tiles[(j*tile_diameter) +
tile_diameter - 1]);
}
} else if ( (p1.lon < p_last.lon) ||
( (p1.lon == p_last.lon) && (p1.x < p_last.x) ) ) {
fgPrintf( FG_TERRAIN, FG_INFO, " Loading %d tiles\n",
tile_diameter);
for ( j = 0; j < tile_diameter; j++ ) {
// scrolling West
for ( i = tile_diameter - 1; i > 0; i-- ) {
tiles[(j*tile_diameter) + i] =
tiles[(j*tile_diameter) + i - 1];
}
// load in new column
fgBucketOffset(&p_last, &p2, -dw - 1, j - dh);
fgTileMgrLoadTile(&p2, &tiles[(j*tile_diameter) + 0]);
}
}
if ( (p1.lat > p_last.lat) ||
( (p1.lat == p_last.lat) && (p1.y > p_last.y) ) ) {
fgPrintf( FG_TERRAIN, FG_INFO, " Loading %d tiles\n",
tile_diameter);
for ( i = 0; i < tile_diameter; i++ ) {
// scrolling North
for ( j = 0; j < tile_diameter - 1; j++ ) {
tiles[(j * tile_diameter) + i] =
tiles[((j+1) * tile_diameter) + i];
}
// load in new column
fgBucketOffset(&p_last, &p2, i - dw, dh + 1);
fgTileMgrLoadTile(&p2, &tiles[((tile_diameter-1) *
tile_diameter) + i]);
}
} else if ( (p1.lat < p_last.lat) ||
( (p1.lat == p_last.lat) && (p1.y < p_last.y) ) ) {
fgPrintf( FG_TERRAIN, FG_INFO, " Loading %d tiles\n",
tile_diameter);
for ( i = 0; i < tile_diameter; i++ ) {
// scrolling South
for ( j = tile_diameter - 1; j > 0; j-- ) {
tiles[(j * tile_diameter) + i] =
tiles[((j-1) * tile_diameter) + i];
}
// load in new column
fgBucketOffset(&p_last, &p2, i - dw, -dh - 1);
fgTileMgrLoadTile(&p2, &tiles[0 + i]);
}
}
}
p_last.lon = p1.lon;
p_last.lat = p1.lat;
p_last.x = p1.x;
p_last.y = p1.y;
return 1;
}
// Calculate shortest distance from point to line
static double point_line_dist_squared( fgPoint3d *tc, fgPoint3d *vp,
MAT3vec d )
{
MAT3vec p, p0;
double dist;
p[0] = tc->x; p[1] = tc->y; p[2] = tc->z;
p0[0] = vp->x; p0[1] = vp->y; p0[2] = vp->z;
dist = fgPointLineSquared(p, p0, d);
// printf("dist = %.2f\n", dist);
return(dist);
}
// Calculate if point/radius is inside view frustum
static int viewable( fgPoint3d *cp, double radius ) {
fgVIEW *v;
MAT3hvec world, eye;
int viewable = 1; // start by assuming it's viewable
double x0, x1, y1, slope;
v = &current_view;
MAT3_SET_HVEC(world, cp->x, cp->y, cp->z, 1.0);
MAT3mult_vec(eye, world, v->WORLD_TO_EYE);
// printf( "\nworld -> eye = %.2f %.2f %.2f radius = %.2f\n",
// eye[0], eye[1], eye[2], radius);
// Check near clip plane
if ( eye[2] - radius > 0.0 ) {
return(0);
}
// Check far clip plane
if ( eye[2] + radius < -current_weather.visibility ) {
return(0);
}
// check right clip plane (from eye perspective)
// y = m * (x - x0) = equation of a line intercepting X axis at x0
x1 = v->cos_fov_x * radius;
y1 = v->sin_fov_x * radius;
slope = v->slope_x;
x0 = x1 - y1 / slope;
// printf("(r) x1 = %.2f y1 = %.2f\n", x1, y1);
// printf("eye[0] = %.2f eye[2] = %.2f\n", eye[0], eye[2]);
// printf("(r) x0 = %.2f slope_x = %.2f radius = %.2f\n",
// x0, slope, radius);
if ( eye[2] > slope * (eye[0] - x0) ) {
return(0);
}
// check left clip plane (from eye perspective)
x1 = -x1;
slope = -slope;
x0 = x1 - y1 / slope;
// printf("(r) x1 = %.2f y1 = %.2f\n", x1, y1);
// printf("eye[0] = %.2f eye[2] = %.2f\n", eye[0], eye[2]);
// printf("(r) x0 = %.2f slope_x = %.2f radius = %.2f\n",
// x0, slope, radius);
if ( eye[2] > slope * (eye[0] - x0) ) {
return(0);
}
// check bottom clip plane (from eye perspective)
x1 = -(v->cos_fov_y) * radius;
y1 = v->sin_fov_y * radius;
slope = v->slope_y;
x0 = x1 - y1 / slope;
// printf("(r) x1 = %.2f y1 = %.2f\n", x1, y1);
// printf("eye[1] = %.2f eye[2] = %.2f\n", eye[1], eye[2]);
// printf("(r) x0 = %.2f slope_y = %.2f radius = %.2f\n",
// x0, slope, radius);
if ( eye[2] > slope * (eye[1] - x0) ) {
return(0);
}
// check top clip plane (from eye perspective)
x1 = -x1;
slope = -slope;
x0 = x1 - y1 / slope;
// printf("(r) x1 = %.2f y1 = %.2f\n", x1, y1);
// printf("eye[1] = %.2f eye[2] = %.2f\n", eye[1], eye[2]);
// printf("(r) x0 = %.2f slope_y = %.2f radius = %.2f\n",
// x0, slope, radius);
if ( eye[2] > slope * (eye[1] - x0) ) {
return(0);
}
return(viewable);
}
// Determine scenery altitude. Normally this just happens when we
// render the scene, but we'd also like to be able to do this
// explicitely. lat & lon are in radians. abs_view_pos in meters.
// Returns result in meters.
double fgTileMgrCurElev( double lon, double lat, fgPoint3d *abs_view_pos ) {
fgTILECACHE *c;
fgTILE *t;
// fgVIEW *v;
fgFRAGMENT *frag_ptr;
fgBUCKET p;
fgPoint3d earth_center, result;
fgPoint3d pp;
MAT3vec local_up;
list < fgFRAGMENT > :: iterator current;
list < fgFRAGMENT > :: iterator last;
double dist, min_dist, lat_geod, alt, sea_level_r;
double x, y, z;
int index, tile_diameter, i;
c = &global_tile_cache;
// v = &current_view;
local_up[0] = abs_view_pos->x;
local_up[1] = abs_view_pos->y;
local_up[2] = abs_view_pos->z;
tile_diameter = current_options.get_tile_diameter();
// Find current translation offset
fgBucketFind(lon * RAD_TO_DEG, lat * RAD_TO_DEG, &p);
index = c->Exists(&p);
t = c->GetTile(index);
scenery.next_center.x = t->center.x;
scenery.next_center.y = t->center.y;
scenery.next_center.z = t->center.z;
earth_center.x = 0.0;
earth_center.y = 0.0;
earth_center.z = 0.0;
fgPrintf( FG_TERRAIN, FG_DEBUG,
"Pos = (%.2f, %.2f) Current bucket = %d %d %d %d Index = %ld\n",
lon * RAD_TO_DEG, lat * RAD_TO_DEG,
p.lon, p.lat, p.x, p.y, fgBucketGenIndex(&p) );
// traverse the potentially viewable tile list
for ( i = 0; i < (tile_diameter * tile_diameter); i++ ) {
index = tiles[i];
// fgPrintf( FG_TERRAIN, FG_DEBUG, "Index = %d\n", index);
t = c->GetTile(index);
// calculate tile offset
x = (t->offset.x = t->center.x - scenery.center.x);
y = (t->offset.y = t->center.y - scenery.center.y);
z = (t->offset.z = t->center.z - scenery.center.z);
// calc current terrain elevation calculate distance from
// vertical tangent line at current position to center of
// tile.
/* printf("distance squared = %.2f, bounding radius = %.2f\n",
point_line_dist_squared(&(t->offset), &(v->view_pos),
v->local_up), t->bounding_radius); */
dist = point_line_dist_squared( &(t->center), abs_view_pos,
local_up );
if ( dist < FG_SQUARE(t->bounding_radius) ) {
// traverse fragment list for tile
current = t->fragment_list.begin();
last = t->fragment_list.end();
while ( current != last ) {
frag_ptr = &(*current);
current++;
/* printf("distance squared = %.2f, bounding radius = %.2f\n",
point_line_dist_squared( &(frag_ptr->center),
&abs_view_pos), local_up),
frag_ptr->bounding_radius); */
dist = point_line_dist_squared( &(frag_ptr->center),
abs_view_pos, local_up);
if ( dist <= FG_SQUARE(frag_ptr->bounding_radius) ) {
if ( frag_ptr->intersect( abs_view_pos,
&earth_center, 0, &result ) ) {
// compute geocentric coordinates of tile center
pp = fgCartToPolar3d(result);
// convert to geodetic coordinates
fgGeocToGeod(pp.lat, pp.radius, &lat_geod,
&alt, &sea_level_r);
// printf("alt = %.2f\n", alt);
// exit since we found an intersection
return(alt);
}
}
}
}
}
printf("no terrain intersection found\n");
return(0);
}
// Render the local tiles
void fgTileMgrRender( void ) {
fgTILECACHE *c;
fgFLIGHT *f;
fgTILE *t, *last_tile_ptr;
fgVIEW *v;
fgBUCKET p;
fgPoint3d frag_offset, pp;
fgPoint3d earth_center, result;
fgFRAGMENT *frag_ptr;
fgMATERIAL *mtl_ptr;
GLdouble *m;
double dist, min_dist, lat_geod, alt, sea_level_r;
double x, y, z;
list < fgFRAGMENT > :: iterator current;
list < fgFRAGMENT > :: iterator last;
int i, j, size;
int tile_diameter, textures;
int index;
int culled = 0;
int drawn = 0;
int total_faces = 0;
c = &global_tile_cache;
f = current_aircraft.flight;
v = &current_view;
tile_diameter = current_options.get_tile_diameter();
textures = current_options.get_textures();
// Find current translation offset
fgBucketFind(FG_Longitude * RAD_TO_DEG, FG_Latitude * RAD_TO_DEG, &p);
index = c->Exists(&p);
t = c->GetTile(index);
scenery.next_center.x = t->center.x;
scenery.next_center.y = t->center.y;
scenery.next_center.z = t->center.z;
earth_center.x = 0.0;
earth_center.y = 0.0;
earth_center.z = 0.0;
fgPrintf( FG_TERRAIN, FG_DEBUG,
"Pos = (%.2f, %.2f) Current bucket = %d %d %d %d Index = %ld\n",
FG_Longitude * RAD_TO_DEG, FG_Latitude * RAD_TO_DEG,
p.lon, p.lat, p.x, p.y, fgBucketGenIndex(&p) );
// initialize the transient per-material fragment lists
material_mgr.init_transient_material_lists();
min_dist = 100000.0;
// Pass 1
// traverse the potentially viewable tile list
for ( i = 0; i < (tile_diameter * tile_diameter); i++ ) {
index = tiles[i];
// fgPrintf( FG_TERRAIN, FG_DEBUG, "Index = %d\n", index);
t = c->GetTile(index);
// calculate tile offset
x = (t->offset.x = t->center.x - scenery.center.x);
y = (t->offset.y = t->center.y - scenery.center.y);
z = (t->offset.z = t->center.z - scenery.center.z);
m = t->model_view;
for ( j = 0; j < 16; j++ ) {
m[j] = v->MODEL_VIEW[j];
}
// Calculate the model_view transformation matrix for this tile
// This is equivalent to doing a glTranslatef(x, y, z);
m[12] = m[0] * x + m[4] * y + m[8] * z + m[12];
m[13] = m[1] * x + m[5] * y + m[9] * z + m[13];
m[14] = m[2] * x + m[6] * y + m[10] * z + m[14];
m[15] = m[3] * x + m[7] * y + m[11] * z + m[15];
// temp ... calc current terrain elevation
// calculate distance from vertical tangent line at
// current position to center of tile.
/* printf("distance squared = %.2f, bounding radius = %.2f\n",
point_line_dist_squared(&(t->offset), &(v->view_pos),
v->local_up), t->bounding_radius); */
dist = point_line_dist_squared( &(t->center), &(v->abs_view_pos),
v->local_up );
if ( dist < FG_SQUARE(t->bounding_radius) ) {
// traverse fragment list for tile
current = t->fragment_list.begin();
last = t->fragment_list.end();
while ( current != last ) {
frag_ptr = &(*current);
current++;
/* printf("distance squared = %.2f, bounding radius = %.2f\n",
point_line_dist_squared( &(frag_ptr->center),
&(v->abs_view_pos), v->local_up),
frag_ptr->bounding_radius); */
dist = point_line_dist_squared( &(frag_ptr->center),
&(v->abs_view_pos), v->local_up);
if ( dist <= FG_SQUARE(frag_ptr->bounding_radius) ) {
if ( frag_ptr->intersect( &(v->abs_view_pos),
&earth_center, 0, &result ) ) {
// compute geocentric coordinates of tile center
pp = fgCartToPolar3d(result);
// convert to geodetic coordinates
fgGeocToGeod(pp.lat, pp.radius, &lat_geod,
&alt, &sea_level_r);
// printf("alt = %.2f\n", alt);
scenery.cur_elev = alt;
// exit this loop since we found an intersection
break;
}
}
}
}
// Course (tile based) culling
if ( viewable(&(t->offset), t->bounding_radius) ) {
// at least a portion of this tile could be viewable
// xglPushMatrix();
// xglTranslatef(t->offset.x, t->offset.y, t->offset.z);
// traverse fragment list for tile
current = t->fragment_list.begin();
last = t->fragment_list.end();
while ( current != last ) {
frag_ptr = &(*current);
current++;
if ( frag_ptr->display_list >= 0 ) {
// Fine (fragment based) culling
frag_offset.x = frag_ptr->center.x - scenery.center.x;
frag_offset.y = frag_ptr->center.y - scenery.center.y;
frag_offset.z = frag_ptr->center.z - scenery.center.z;
if ( viewable(&frag_offset, frag_ptr->bounding_radius*2) ) {
// add to transient per-material property fragment list
// frag_ptr->tile_offset.x = t->offset.x;
// frag_ptr->tile_offset.y = t->offset.y;
// frag_ptr->tile_offset.z = t->offset.z;
mtl_ptr = frag_ptr->material_ptr;
// printf(" lookup = %s\n", mtl_ptr->texture_name);
if ( mtl_ptr->list_size < FG_MAX_MATERIAL_FRAGS ) {
mtl_ptr->list[mtl_ptr->list_size] = frag_ptr;
(mtl_ptr->list_size)++;
} else {
fgPrintf( FG_TERRAIN, FG_ALERT,
"Overran material sorting array\n" );
}
// xglCallList(frag_ptr->display_list);
drawn++;
} else {
// printf("Culled a fragment %.2f %.2f %.2f %.2f\n",
// frag_ptr->center.x, frag_ptr->center.y,
// frag_ptr->center.z, frag_ptr->bounding_radius);
culled++;
}
}
}
// xglPopMatrix();
} else {
culled += t->fragment_list.size();
}
}
if ( (drawn + culled) > 0 ) {
v->vfc_ratio = (double)culled / (double)(drawn + culled);
} else {
v->vfc_ratio = 0.0;
}
// printf("drawn = %d culled = %d saved = %.2f\n", drawn, culled,
// v->vfc_ratio);
// Pass 2
// traverse the transient per-material fragment lists and render
// out all fragments for each material property.
map < string, fgMATERIAL, less<string> > :: iterator mapcurrent =
material_mgr.material_map.begin();
map < string, fgMATERIAL, less<string> > :: iterator maplast =
material_mgr.material_map.end();
xglPushMatrix();
while ( mapcurrent != maplast ) {
// (char *)key = (*mapcurrent).first;
// (fgMATERIAL)value = (*mapcurrent).second;
mtl_ptr = &(*mapcurrent).second;
last_tile_ptr = NULL;
size = mtl_ptr->list_size;
if ( size > 0 ) {
if ( textures ) {
#ifdef GL_VERSION_1_1
xglBindTexture(GL_TEXTURE_2D, mtl_ptr->texture_id);
#elif GL_EXT_texture_object
xglBindTextureEXT(GL_TEXTURE_2D, mtl_ptr->texture_id);
#else
# error port me
#endif
} else {
xglMaterialfv (GL_FRONT, GL_AMBIENT, mtl_ptr->ambient);
xglMaterialfv (GL_FRONT, GL_DIFFUSE, mtl_ptr->diffuse);
}
// printf("traversing = %s, size = %d\n",
// mtl_ptr->texture_name, size);
for ( i = 0; i < size; i++ ) {
frag_ptr = mtl_ptr->list[i];
// count up the number of polygons we are drawing in
// case someone is interested.
total_faces += frag_ptr->num_faces;
if ( frag_ptr->tile_ptr == last_tile_ptr ) {
// same tile as last time, no transform necessary
} else {
// new tile, new translate
// xglLoadMatrixf( frag_ptr->matrix );
t = frag_ptr->tile_ptr;
xglLoadMatrixd(t->model_view );
}
// Woohoo!!! We finally get to draw something!
// printf(" display_list = %d\n", frag_ptr->display_list);
xglCallList(frag_ptr->display_list);
last_tile_ptr = frag_ptr->tile_ptr;
}
}
*mapcurrent++;
}
xglPopMatrix();
fgPrintf( FG_TERRAIN, FG_DEBUG, "Rendered %d polygons this frame.\n",
total_faces);
}
// $Log$
// Revision 1.30 1998/08/22 14:49:59 curt
// Attempting to iron out seg faults and crashes.
// Did some shuffling to fix a initialization order problem between view
// position, scenery elevation.
//
// Revision 1.29 1998/08/20 15:12:06 curt
// Used a forward declaration of classes fgTILE and fgMATERIAL to eliminate
// the need for "void" pointers and casts.
// Quick hack to count the number of scenery polygons that are being drawn.
//
// Revision 1.28 1998/08/12 21:13:06 curt
// material.cxx: don't load textures if they are disabled
// obj.cxx: optimizations from Norman Vine
// tile.cxx: minor tweaks
// tile.hxx: addition of num_faces
// tilemgr.cxx: minor tweaks
//
// Revision 1.27 1998/07/24 21:42:09 curt
// material.cxx: whups, double method declaration with no definition.
// obj.cxx: tweaks to avoid errors in SGI's CC.
// tile.cxx: optimizations by Norman Vine.
// tilemgr.cxx: optimizations by Norman Vine.
//
// Revision 1.26 1998/07/20 12:51:26 curt
// Added far clip plane to fragment clipping calculations and tie this to
// weather->visibility. This way you can increase framerates by increasing
// for and lowering visibility.
//
// Revision 1.25 1998/07/13 21:02:01 curt
// Wrote access functions for current fgOPTIONS.
//
// Revision 1.24 1998/07/12 03:18:29 curt
// Added ground collision detection. This involved:
// - saving the entire vertex list for each tile with the tile records.
// - saving the face list for each fragment with the fragment records.
// - code to intersect the current vertical line with the proper face in
// an efficient manner as possible.
// Fixed a bug where the tiles weren't being shifted to "near" (0,0,0)
//
// Revision 1.23 1998/07/08 14:47:23 curt
// Fix GL_MODULATE vs. GL_DECAL problem introduced by splash screen.
// polare3d.h renamed to polar3d.hxx
// fg{Cartesian,Polar}Point3d consolodated.
// Added some initial support for calculating local current ground elevation.
//
// Revision 1.22 1998/07/04 00:54:31 curt
// Added automatic mipmap generation.
//
// When rendering fragments, use saved model view matrix from associated tile
// rather than recalculating it with push() translate() pop().
//
// Revision 1.21 1998/06/27 16:54:59 curt
// Check for GL_VERSION_1_1 or GL_EXT_texture_object to decide whether to use
// "EXT" versions of texture management routines.
//
// Revision 1.20 1998/06/17 21:36:42 curt
// Load and manage multiple textures defined in the Materials library.
// Boost max material fagments for each material property to 800.
// Multiple texture support when rendering.
//
// Revision 1.19 1998/06/08 17:57:54 curt
// Working first pass at material proporty sorting.
//
// Revision 1.18 1998/06/06 01:09:32 curt
// I goofed on the log message in the last commit ... now fixed.
//
// Revision 1.17 1998/06/06 01:07:18 curt
// Increased per material fragment list size from 100 to 400.
// Now correctly draw viewable fragments in per material order.
//
// Revision 1.16 1998/06/05 22:39:55 curt
// Working on sorting by, and rendering by material properties.
//
// Revision 1.15 1998/06/03 00:47:51 curt
// No .h for STL includes.
// Minor view culling optimizations.
//
// Revision 1.14 1998/06/01 17:56:20 curt
// Incremental additions to material.cxx (not fully functional)
// Tweaked vfc_ratio math to avoid divide by zero.
//
// Revision 1.13 1998/05/24 02:49:10 curt
// Implimented fragment level view frustum culling.
//
// Revision 1.12 1998/05/23 14:09:23 curt
// Added tile.cxx and tile.hxx.
// Working on rewriting the tile management system so a tile is just a list
// fragments, and the fragment record contains the display list for that fragment.
//
// Revision 1.11 1998/05/20 20:53:55 curt
// Moved global ref point and radius (bounding sphere info, and offset) to
// data file rather than calculating it on the fly.
// Fixed polygon winding problem in scenery generation stage rather than
// compensating for it on the fly.
// Made a fgTILECACHE class.
//
// Revision 1.10 1998/05/17 16:59:34 curt
// Frist pass at view frustum culling now operational.
//
// Revision 1.9 1998/05/16 13:09:58 curt
// Beginning to add support for view frustum culling.
// Added some temporary code to calculate bouding radius, until the
// scenery generation tools and scenery can be updated.
//
// Revision 1.8 1998/05/07 23:15:21 curt
// Fixed a glTexImage2D() usage bug where width and height were mis-swapped.
// Added support for --tile-radius=n option.
//
// Revision 1.7 1998/05/06 03:16:42 curt
// Added an option to control square tile radius.
//
// Revision 1.6 1998/05/02 01:52:18 curt
// Playing around with texture coordinates.
//
// Revision 1.5 1998/04/30 12:35:32 curt
// Added a command line rendering option specify smooth/flat shading.
//
// Revision 1.4 1998/04/27 03:30:14 curt
// Minor transformation adjustments to try to keep scenery tiles closer to
// (0, 0, 0) GLfloats run out of precision at the distances we need to model
// the earth, but we can do a bunch of pre-transformations using double math
// and then cast to GLfloat once everything is close in where we have less
// precision problems.
//
// Revision 1.3 1998/04/25 22:06:32 curt
// Edited cvs log messages in source files ... bad bad bad!
//
// Revision 1.2 1998/04/24 00:51:09 curt
// Wrapped "#include <config.h>" in "#ifdef HAVE_CONFIG_H"
// Tweaked the scenery file extentions to be "file.obj" (uncompressed)
// or "file.obz" (compressed.)
//
// Revision 1.1 1998/04/22 13:22:48 curt
// C++ - ifing the code a bit.
//
// Revision 1.25 1998/04/18 04:14:07 curt
// Moved fg_debug.c to it's own library.
//
// Revision 1.24 1998/04/14 02:23:18 curt
// Code reorganizations. Added a Lib/ directory for more general libraries.
//
// Revision 1.23 1998/04/08 23:30:08 curt
// Adopted Gnu automake/autoconf system.
//
// Revision 1.22 1998/04/03 22:11:38 curt
// Converting to Gnu autoconf system.
//
// Revision 1.21 1998/03/23 21:23:05 curt
// Debugging output tweaks.
//
// Revision 1.20 1998/03/14 00:30:51 curt
// Beginning initial terrain texturing experiments.
//
// Revision 1.19 1998/02/20 00:16:25 curt
// Thursday's tweaks.
//
// Revision 1.18 1998/02/19 13:05:54 curt
// Incorporated some HUD tweaks from Michelle America.
// Tweaked the sky's sunset/rise colors.
// Other misc. tweaks.
//
// Revision 1.17 1998/02/16 13:39:46 curt
// Miscellaneous weekend tweaks. Fixed? a cache problem that caused whole
// tiles to occasionally be missing.
//
// Revision 1.16 1998/02/12 21:59:53 curt
// Incorporated code changes contributed by Charlie Hotchkiss
// <chotchkiss@namg.us.anritsu.com>
//
// Revision 1.14 1998/02/09 21:30:19 curt
// Fixed a nagging problem with terrain tiles not "quite" matching up perfectly.
//
// Revision 1.13 1998/02/07 15:29:46 curt
// Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
// <chotchkiss@namg.us.anritsu.com>
//
// Revision 1.12 1998/02/01 03:39:55 curt
// Minor tweaks.
//
// Revision 1.11 1998/01/31 00:43:27 curt
// Added MetroWorks patches from Carmen Volpe.
//
// Revision 1.10 1998/01/29 00:51:40 curt
// First pass at tile cache, dynamic tile loading and tile unloading now works.
//
// Revision 1.9 1998/01/27 03:26:44 curt
// Playing with new fgPrintf command.
//
// Revision 1.8 1998/01/27 00:48:04 curt
// Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
// system and commandline/config file processing code.
//
// Revision 1.7 1998/01/26 15:55:25 curt
// Progressing on building dynamic scenery system.
//
// Revision 1.6 1998/01/24 00:03:30 curt
// Initial revision.
//
// Revision 1.5 1998/01/19 19:27:18 curt
// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
// This should simplify things tremendously.
//
// Revision 1.4 1998/01/19 18:40:38 curt
// Tons of little changes to clean up the code and to remove fatal errors
// when building with the c++ compiler.
//
// Revision 1.3 1998/01/13 00:23:11 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 1.2 1998/01/08 02:22:27 curt
// Continue working on basic features.
//
// Revision 1.1 1998/01/07 23:50:51 curt
// "area" renamed to "tile"
//
// Revision 1.2 1998/01/07 03:29:29 curt
// Given an arbitrary lat/lon, we can now:
// 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.
//
// Revision 1.1 1998/01/07 02:05:48 curt
// Initial revision.