flightgear/Objects/obj.cxx

// obj.cxx -- routines to handle "sorta" WaveFront .obj format files.
//
// 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 HAVE_CONFIG_H
#  include <config.h>
#endif

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

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

// #if defined ( __sun__ )
// extern "C" void *memmove(void *, const void *, size_t);
// extern "C" void *memset(void *, int, size_t);
// #endif

#include <Include/compiler.h>

#include STL_STRING
#include <map>          // STL
#include <ctype.h>      // isdigit()

#include <Debug/logstream.hxx>
#include <Misc/fgstream.hxx>
#include <Include/fg_constants.h>
#include <Main/options.hxx>
#include <Math/mat3.h>
#include <Math/fg_random.h>
#include <Math/point3d.hxx>
#include <Math/polar3d.hxx>
#include <Misc/stopwatch.hxx>
#include <Scenery/tile.hxx>

#include "material.hxx"
#include "obj.hxx"

FG_USING_STD(string);


static double normals[MAX_NODES][3];


// given three points defining a triangle, calculate the normal
static void calc_normal(double p1[3], double p2[3], 
			double p3[3], double normal[3])
{
    double v1[3], v2[3];
    double temp;

    v1[0] = p2[0] - p1[0]; v1[1] = p2[1] - p1[1]; v1[2] = p2[2] - p1[2];
    v2[0] = p3[0] - p1[0]; v2[1] = p3[1] - p1[1]; v2[2] = p3[2] - p1[2];

    MAT3cross_product(normal, v1, v2);
    MAT3_NORMALIZE_VEC(normal,temp);

    // fgPrintf( FG_TERRAIN, FG_DEBUG, "  Normal = %.2f %.2f %.2f\n", 
    //           normal[0], normal[1], normal[2]);
}


#define FG_TEX_CONSTANT 69.0


// Calculate texture coordinates for a given point.
static Point3D calc_tex_coords(double *node, const Point3D& ref) {
    Point3D cp;
    Point3D pp;
    // double tmplon, tmplat;

    // cout << "-> " << node[0] << " " << node[1] << " " << node[2] << endl;
    // cout << "-> " << ref.x() << " " << ref.y() << " " << ref.z() << endl;

    cp = Point3D( node[0] + ref.x(),
		  node[1] + ref.y(),
		  node[2] + ref.z() );

    pp = fgCartToPolar3d(cp);

    // tmplon = pp.lon() * RAD_TO_DEG;
    // tmplat = pp.lat() * RAD_TO_DEG;
    // cout << tmplon << " " << tmplat << endl;

    pp.setx( fmod(RAD_TO_DEG * FG_TEX_CONSTANT * pp.x(), 11.0) );
    pp.sety( fmod(RAD_TO_DEG * FG_TEX_CONSTANT * pp.y(), 11.0) );

    if ( pp.x() < 0.0 ) {
	pp.setx( pp.x() + 11.0 );
    }

    if ( pp.y() < 0.0 ) {
	pp.sety( pp.y() + 11.0 );
    }

    // cout << pp << endl;

    return(pp);
}


// Load a .obj file and build the GL fragment list
int fgObjLoad( const string& path, fgTILE *t) {
    fgFRAGMENT fragment;
    Point3D pp;
    double approx_normal[3], normal[3] /*, scale = 0.0 */;
    // double x, y, z, xmax, xmin, ymax, ymin, zmax, zmin;
    // GLfloat sgenparams[] = { 1.0, 0.0, 0.0, 0.0 };
    GLint display_list = 0;
    int shading;
    int in_fragment = 0, in_faces = 0, vncount;
    int n1 = 0, n2 = 0, n3 = 0, n4 = 0;
    int last1 = 0, last2 = 0, odd = 0;
    double (*nodes)[3];
    Point3D center;

    // printf("loading %s\n", path.c_str() );

    // Attempt to open "path.gz" or "path"
    fg_gzifstream in( path );
    if ( ! in ) {
	FG_LOG( FG_TERRAIN, FG_ALERT, "Cannot open file: " << path );
	return 0;
    }

    shading = current_options.get_shading();

    in_fragment = 0;
    t->ncount = 0;
    vncount = 0;
    t->bounding_radius = 0.0;
    nodes = t->nodes;
    center = t->center;

    StopWatch stopwatch;
    stopwatch.start();

    // ignore initial comments and blank lines. (priming the pump)
    // in >> skipcomment;
    string line;

    while ( ! in.eof() ) {
	string token;
	char c;

	in >> skipws;

	if ( in.get( c ) && c == '#' ) {
	    // process a comment line

	    // getline( in, line );
	    // cout << "comment = " << line << endl;

	    in >> token;

	    if ( token == "gbs" ) {
		// reference point (center offset)
		in >> t->center >> t->bounding_radius;
		center = t->center;
		// cout << "center = " << center 
		//      << " radius = " << t->bounding_radius << endl;
	    } else if ( token == "bs" )	{
		// reference point (center offset)
		in >> fragment.center;
		in >> fragment.bounding_radius;

		// cout << "center = " << fragment.center 
		//      << " radius = " << fragment.bounding_radius << endl;
	    } else if ( token == "usemtl" ) {
		// material property specification

		// series of individual triangles
		if ( in_faces ) {
		    xglEnd();
		}

		// this also signals the start of a new fragment
		if ( in_fragment ) {
		    // close out the previous structure and start the next
		    xglEndList();
		    // printf("xglEnd(); xglEndList();\n");

		    // update fragment
		    fragment.display_list = display_list;

		    // push this fragment onto the tile's object list
		    t->fragment_list.push_back(fragment);
		} else {
		    in_fragment = 1;
		}

		// printf("start of fragment (usemtl)\n");

		display_list = xglGenLists(1);
		xglNewList(display_list, GL_COMPILE);
		// printf("xglGenLists(); xglNewList();\n");
		in_faces = 0;

		// reset the existing face list
		// printf("cleaning a fragment with %d faces\n", 
		//        fragment.faces.size());
		fragment.init();
		
		// scan the material line
		string material;
		in >> material;
		fragment.tile_ptr = t;
		
		// find this material in the properties list
		if ( ! material_mgr.find( material, fragment.material_ptr )) {
		    FG_LOG( FG_TERRAIN, FG_ALERT, 
			    "Ack! unknown usemtl name = " << material 
			    << " in " << path );
		}
		
		// initialize the fragment transformation matrix
		/*
		 for ( i = 0; i < 16; i++ ) {
	           fragment.matrix[i] = 0.0;
	         }
	         fragment.matrix[0] = fragment.matrix[5] =
		 fragment.matrix[10] = fragment.matrix[15] = 1.0;
	        */
	    } else {
		// unknown comment, just gobble the input untill the
		// end of line

		in >> skipeol;
	    }
	} else {
	    in.putback( c );
	
	    in >> token;

	    // cout << "token = " << token << endl;

	    if ( token == "vn" ) {
		// vertex normal
		if ( vncount < MAX_NODES ) {
		    in >> normals[vncount][0]
		       >> normals[vncount][1]
		       >> normals[vncount][2];
		    vncount++;
		} else {
		    FG_LOG( FG_TERRAIN, FG_ALERT, 
			    "Read too many vertex normals ... dying :-(" );
		    exit(-1);
		}
	    } else if ( token == "v" ) {
		// node (vertex)
		if ( t->ncount < MAX_NODES ) {
		    in >> t->nodes[t->ncount][0]
		       >> t->nodes[t->ncount][1]
		       >> t->nodes[t->ncount][2];
		    t->ncount++;
		} else {
		    FG_LOG( FG_TERRAIN, FG_ALERT, 
			    "Read too many nodes ... dying :-(");
		    exit(-1);
		}
	    } else if ( token == "t" ) {
		// start a new triangle strip

		n1 = n2 = n3 = n4 = 0;

		// fgPrintf( FG_TERRAIN, FG_DEBUG, 
		//           "    new tri strip = %s", line);
		in >> n1 >> n2 >> n3;
		fragment.add_face(n1, n2, n3);

		// fgPrintf( FG_TERRAIN, FG_DEBUG, "(t) = ");

		xglBegin(GL_TRIANGLE_STRIP);
		// printf("xglBegin(tristrip) %d %d %d\n", n1, n2, n3);

		odd = 1; 
		// scale = 1.0;

		if ( shading ) {
		    // Shading model is "GL_SMOOTH" so use precalculated
		    // (averaged) normals
		    // MAT3_SCALE_VEC(normal, normals[n1], scale);
		    xglNormal3dv(normal);
		    pp = calc_tex_coords(nodes[n1], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n1]);		

		    // MAT3_SCALE_VEC(normal, normals[n2], scale);
		    xglNormal3dv(normal);
		    pp = calc_tex_coords(nodes[n2], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n2]);				

		    // MAT3_SCALE_VEC(normal, normals[n3], scale);
		    xglNormal3dv(normal);
		    pp = calc_tex_coords(nodes[n3], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n3]);
		} else {
		    // Shading model is "GL_FLAT" so calculate per face
		    // normals on the fly.
		    if ( odd ) {
			calc_normal(nodes[n1], nodes[n2], 
				    nodes[n3], approx_normal);
		    } else {
			calc_normal(nodes[n2], nodes[n1], 
				    nodes[n3], approx_normal);
		    }
		    // MAT3_SCALE_VEC(normal, approx_normal, scale);
		    xglNormal3dv(normal);

		    pp = calc_tex_coords(nodes[n1], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n1]);		

		    pp = calc_tex_coords(nodes[n2], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n2]);		
		    
		    pp = calc_tex_coords(nodes[n3], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n3]);		
		}
		// printf("some normals, texcoords, and vertices\n");

		odd = 1 - odd;
		last1 = n2;
		last2 = n3;

		// There can be three or four values 
		char c;
		while ( in.get(c) ) {
		    if ( c == '\n' ) {
			break; // only the one
		    }
		    if ( isdigit(c) ){
			in.putback(c);
			in >> n4;
			break;
		    }
		}

		if ( n4 > 0 ) {
		    fragment.add_face(n3, n2, n4);

		    if ( shading ) {
			// Shading model is "GL_SMOOTH"
			// MAT3_SCALE_VEC(normal, normals[n4], scale);
		    } else {
			// Shading model is "GL_FLAT"
			calc_normal(nodes[n3], nodes[n2], nodes[n4], 
				    approx_normal);
			// MAT3_SCALE_VEC(normal, approx_normal, scale);
		    }
		    xglNormal3dv(normal);
		    pp = calc_tex_coords(nodes[n4], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n4]);		
		    
		    odd = 1 - odd;
		    last1 = n3;
		    last2 = n4;
		    // printf("a normal, texcoord, and vertex (4th)\n");
		}
	    } else if ( token == "tf" ) {
		// triangle fan
		// fgPrintf( FG_TERRAIN, FG_DEBUG, "new fan");

		xglBegin(GL_TRIANGLE_FAN);

		in >> n1;
		xglNormal3dv(normals[n1]);
		pp = calc_tex_coords(nodes[n1], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n1]);

		in >> n2;
		xglNormal3dv(normals[n2]);
		pp = calc_tex_coords(nodes[n2], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n2]);
		
		// read all subsequent numbers until next thing isn't a number
		while ( true ) {
		    in >> skipws;

		    char c;
		    in.get(c);
		    in.putback(c);
		    if ( ! isdigit(c) || in.eof() ) {
			break;
		    }

		    in >> n3;
		    cout << "  triangle = " 
			 << n1 << "," << n2 << "," << n3 
			 << endl;
		    xglNormal3dv(normals[n3]);
		    pp = calc_tex_coords(nodes[n3], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n3]);

		    fragment.add_face(n1, n2, n3);
		    n2 = n3;
		}

		xglEnd();
	    } else if ( token == "f" ) {
		// unoptimized face

		if ( !in_faces ) {
		    xglBegin(GL_TRIANGLES);
		    // printf("xglBegin(triangles)\n");
		    in_faces = 1;
		}

		// fgPrintf( FG_TERRAIN, FG_DEBUG, "new triangle = %s", line);*/
		in >> n1 >> n2 >> n3;
		fragment.add_face(n1, n2, n3);

		// xglNormal3d(normals[n1][0], normals[n1][1], normals[n1][2]);
		xglNormal3dv(normals[n1]);
		pp = calc_tex_coords(nodes[n1], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n1]);

		xglNormal3dv(normals[n2]);
		pp = calc_tex_coords(nodes[n2], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n2]);
		
		xglNormal3dv(normals[n3]);
		pp = calc_tex_coords(nodes[n3], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n3]);
		// printf("some normals, texcoords, and vertices (tris)\n");
	    } else if ( token == "q" ) {
		// continue a triangle strip
		n1 = n2 = 0;

		// fgPrintf( FG_TERRAIN, FG_DEBUG, "continued tri strip = %s ", 
		//           line);
		in >> n1;

		// There can be one or two values 
		char c;
		while ( in.get(c) ) {
		    if ( c == '\n' ) {
			break; // only the one
		    }

		    if ( isdigit(c) ) {
			in.putback(c);
			in >> n2;
			break;
		    }
		}
		// fgPrintf( FG_TERRAIN, FG_DEBUG, "read %d %d\n", n1, n2);

		if ( odd ) {
		    fragment.add_face(last1, last2, n1);
		} else {
		    fragment.add_face(last2, last1, n1);
		}

		if ( shading ) {
		    // Shading model is "GL_SMOOTH"
		    // MAT3_SCALE_VEC(normal, normals[n1], scale);
		} else {
		    // Shading model is "GL_FLAT"
		    if ( odd ) {
			calc_normal(nodes[last1], nodes[last2], nodes[n1], 
				    approx_normal);
		    } else {
			calc_normal(nodes[last2], nodes[last1], nodes[n1], 
				    approx_normal);
		    }
		    // MAT3_SCALE_VEC(normal, approx_normal, scale);
		}
		xglNormal3dv(normal);

		pp = calc_tex_coords(nodes[n1], center);
		xglTexCoord2f(pp.lon(), pp.lat());
		xglVertex3dv(nodes[n1]);
		// printf("a normal, texcoord, and vertex (4th)\n");
   
		odd = 1 - odd;
		last1 = last2;
		last2 = n1;

		if ( n2 > 0 ) {
		    // fgPrintf( FG_TERRAIN, FG_DEBUG, " (cont)\n");

		    if ( odd ) {
			fragment.add_face(last1, last2, n2);
		    } else {
			fragment.add_face(last2, last1, n2);
		    }

		    if ( shading ) {
			// Shading model is "GL_SMOOTH"
			// MAT3_SCALE_VEC(normal, normals[n2], scale);
		    } else {
			// Shading model is "GL_FLAT"
			if ( odd ) {
			    calc_normal(nodes[last1], nodes[last2], 
					nodes[n2], approx_normal);
			} else {
			    calc_normal(nodes[last2], nodes[last1], 
					nodes[n2], approx_normal);
			}
			// MAT3_SCALE_VEC(normal, approx_normal, scale);
		    }
		    xglNormal3dv(normal);
		
		    pp = calc_tex_coords(nodes[n2], center);
		    xglTexCoord2f(pp.lon(), pp.lat());
		    xglVertex3dv(nodes[n2]);		
		    // printf("a normal, texcoord, and vertex (4th)\n");

		    odd = 1 -odd;
		    last1 = last2;
		    last2 = n2;
		}
	    } else {
		FG_LOG( FG_TERRAIN, FG_WARN, "Unknown token in " 
			<< path << " = " << token );
	    }

	    // eat white space before start of while loop so if we are
	    // done with useful input it is noticed before hand.
	    in >> skipws;
	}
    }

    if ( in_fragment ) {
	// close out the previous structure and start the next
	xglEnd();
	xglEndList();
	// printf("xglEnd(); xglEndList();\n");
	
	// update fragment
	fragment.display_list = display_list;
	
	// push this fragment onto the tile's object list
	t->fragment_list.push_back(fragment);
    }

#if 0
    // Draw normal vectors (for visually verifying normals)
    xglBegin(GL_LINES);
    xglColor3f(0.0, 0.0, 0.0);
    for ( i = 0; i < t->ncount; i++ ) {
	xglVertex3d(t->nodes[i][0],
		    t->nodes[i][1] ,
 		    t->nodes[i][2]);
	xglVertex3d(t->nodes[i][0] + 500*normals[i][0],
 		    t->nodes[i][1] + 500*normals[i][1],
 		    t->nodes[i][2] + 500*normals[i][2]);
    } 
    xglEnd();
#endif

    stopwatch.stop();
    FG_LOG( FG_TERRAIN, FG_INFO, 
	    "Loaded " << path << " in " 
	    << stopwatch.elapsedSeconds() << " seconds" );
    
    return 1;
}


// $Log$
// Revision 1.14  1999/03/30 23:48:24  curt
// modifications to obj loader to handle tri fans.
//
// Revision 1.13  1999/03/27 05:36:03  curt
// Alas, I have made non-backwardsly compatible changes to the scenery file
//   format.  Thus I have had to make the corresponding changes here in the
//   file loader.
// Things that do not correspond the the .obj format are placed in comments.
//
// Revision 1.12  1999/03/02 01:03:25  curt
// Tweaks for building with native SGI compilers.
//
// Revision 1.11  1999/02/26 22:09:59  curt
// Added initial support for native SGI compilers.
//
// Revision 1.10  1998/11/06 21:18:18  curt
// Converted to new logstream debugging facility.  This allows release
// builds with no messages at all (and no performance impact) by using
// the -DFG_NDEBUG flag.
//
// Revision 1.9  1998/11/06 14:47:06  curt
// Changes to track Bernie's updates to fgstream.
//
// Revision 1.8  1998/10/20 18:33:55  curt
// Tweaked texture coordinates, but we still have some problems. :-(
//
// Revision 1.7  1998/10/20 15:48:44  curt
// Removed an extraneous output message.
//
// Revision 1.6  1998/10/18 01:17:21  curt
// Point3D tweaks.
//
// Revision 1.5  1998/10/16 00:54:39  curt
// Converted to Point3D class.
//
// Revision 1.4  1998/09/15 01:35:07  curt
// cleaned up my fragment.num_faces hack :-) to use the STL (no need in
// duplicating work.)
// Tweaked fgTileMgrRender() do not calc tile matrix unless necessary.
// removed some unneeded stuff from fgTileMgrCurElev()
//
// Revision 1.3  1998/09/03 21:27:03  curt
// Fixed a serious bug caused by not-quite-correct comment/white space eating
// which resulted in mismatched glBegin() glEnd() pairs, incorrect display lists,
// and ugly display artifacts.
//
// Revision 1.2  1998/09/01 19:03:09  curt
// Changes contributed by Bernie Bright <bbright@c031.aone.net.au>
//  - The new classes in libmisc.tgz define a stream interface into zlib.
//    I've put these in a new directory, Lib/Misc.  Feel free to rename it
//    to something more appropriate.  However you'll have to change the
//    include directives in all the other files.  Additionally you'll have
//    add the library to Lib/Makefile.am and Simulator/Main/Makefile.am.
//
//    The StopWatch class in Lib/Misc requires a HAVE_GETRUSAGE autoconf
//    test so I've included the required changes in config.tgz.
//
//    There are a fair few changes to Simulator/Objects as I've moved
//    things around.  Loading tiles is quicker but thats not where the delay
//    is.  Tile loading takes a few tenths of a second per file on a P200
//    but it seems to be the post-processing that leads to a noticeable
//    blip in framerate.  I suppose its time to start profiling to see where
//    the delays are.
//
//    I've included a brief description of each archives contents.
//
// Lib/Misc/
//   zfstream.cxx
//   zfstream.hxx
//     C++ stream interface into zlib.
//     Taken from zlib-1.1.3/contrib/iostream/.
//     Minor mods for STL compatibility.
//     There's no copyright associated with these so I assume they're
//     covered by zlib's.
//
//   fgstream.cxx
//   fgstream.hxx
//     FlightGear input stream using gz_ifstream.  Tries to open the
//     given filename.  If that fails then filename is examined and a
//     ".gz" suffix is removed or appended and that file is opened.
//
//   stopwatch.hxx
//     A simple timer for benchmarking.  Not used in production code.
//     Taken from the Blitz++ project.  Covered by GPL.
//
//   strutils.cxx
//   strutils.hxx
//     Some simple string manipulation routines.
//
// Simulator/Airports/
//   Load airports database using fgstream.
//   Changed fgAIRPORTS to use set<> instead of map<>.
//   Added bool fgAIRPORTS::search() as a neater way doing the lookup.
//   Returns true if found.
//
// Simulator/Astro/
//   Modified fgStarsInit() to load stars database using fgstream.
//
// Simulator/Objects/
//   Modified fgObjLoad() to use fgstream.
//   Modified fgMATERIAL_MGR::load_lib() to use fgstream.
//   Many changes to fgMATERIAL.
//   Some changes to fgFRAGMENT but I forget what!
//
// Revision 1.1  1998/08/25 16:51:25  curt
// Moved from ../Scenery
//
// Revision 1.23  1998/08/20 15:16:43  curt
// obj.cxx: use more explicit parenthases.
// texload.[ch]: use const in function definitions where appropriate.
//
// Revision 1.22  1998/08/20 15:12:03  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 1.21  1998/08/12 21:13:04  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 1.20  1998/07/24 21:42:07  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 1.19  1998/07/13 21:01:58  curt
// Wrote access functions for current fgOPTIONS.
//
// Revision 1.18  1998/07/12 03:18:27  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 1.17  1998/07/08 14:47:21  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 1.16  1998/07/06 21:34:33  curt
// Added using namespace std for compilers that support this.
//
// Revision 1.15  1998/07/04 00:54:28  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 1.14  1998/06/17 21:36:40  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 1.13  1998/06/12 00:58:05  curt
// Build only static libraries.
// Declare memmove/memset for Sloaris.
//
// Revision 1.12  1998/06/08 17:57:54  curt
// Working first pass at material proporty sorting.
//
// Revision 1.11  1998/06/06 01:09:31  curt
// I goofed on the log message in the last commit ... now fixed.
//
// Revision 1.10  1998/06/06 01:07:17  curt
// Increased per material fragment list size from 100 to 400.
// Now correctly draw viewable fragments in per material order.
//
// Revision 1.9  1998/06/05 22:39:54  curt
// Working on sorting by, and rendering by material properties.
//
// Revision 1.8  1998/06/05 18:19:18  curt
// Recognize file, file.gz, and file.obj as scenery object files.
//
// Revision 1.7  1998/05/24 02:49:09  curt
// Implimented fragment level view frustum culling.
//
// Revision 1.6  1998/05/23 14:09:20  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 1.5  1998/05/20 20:53:53  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 1.4  1998/05/16 13:09:57  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 1.3  1998/05/03 00:48:01  curt
// Updated texture coordinate fmod() parameter.
//
// Revision 1.2  1998/05/02 01:52:14  curt
// Playing around with texture coordinates.
//
// Revision 1.1  1998/04/30 12:35:28  curt
// Added a command line rendering option specify smooth/flat shading.
//
// Revision 1.35  1998/04/28 21:43:26  curt
// Wrapped zlib calls up so we can conditionally comment out zlib support.
//
// Revision 1.34  1998/04/28 01:21:42  curt
// Tweaked texture parameter calculations to keep the number smaller.  This
// avoids the "swimming" problem.
// Type-ified fgTIME and fgVIEW.
//
// Revision 1.33  1998/04/27 15:58:15  curt
// Screwing around with texture coordinate generation ... still needs work.
//
// Revision 1.32  1998/04/27 03:30:13  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 1.31  1998/04/25 15:09:57  curt
// Changed "r" to "rb" in gzopen() options.  This fixes bad behavior in win32.
//
// Revision 1.30  1998/04/24 14:21:08  curt
// Added "file.obj.gz" support.
//
// Revision 1.29  1998/04/24 00:51:07  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 1.28  1998/04/22 13:22:44  curt
// C++ - ifing the code a bit.
//
// Revision 1.27  1998/04/18 04:13:17  curt
// Added zlib on the fly decompression support for loading scenery objects.
//
// Revision 1.26  1998/04/03 22:11:36  curt
// Converting to Gnu autoconf system.
//
// Revision 1.25  1998/03/14 00:30:50  curt
// Beginning initial terrain texturing experiments.
//
// Revision 1.24  1998/02/09 21:30:18  curt
// Fixed a nagging problem with terrain tiles not "quite" matching up perfectly.
//
// Revision 1.23  1998/02/09 15:07:52  curt
// Minor tweaks.
//
// Revision 1.22  1998/02/01 03:39:54  curt
// Minor tweaks.
//
// Revision 1.21  1998/01/31 00:43:25  curt
// Added MetroWorks patches from Carmen Volpe.
//
// Revision 1.20  1998/01/29 00:51:39  curt
// First pass at tile cache, dynamic tile loading and tile unloading now works.
//
// Revision 1.19  1998/01/27 03:26:42  curt
// Playing with new fgPrintf command.
//
// Revision 1.18  1998/01/19 19:27:16  curt
// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
// This should simplify things tremendously.
//
// Revision 1.17  1998/01/13 00:23:10  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 1.16  1997/12/30 23:09:40  curt
// Worked on winding problem without luck, so back to calling glFrontFace()
// 3 times for each scenery area.
//
// Revision 1.15  1997/12/30 20:47:51  curt
// Integrated new event manager with subsystem initializations.
//
// Revision 1.14  1997/12/30 01:38:46  curt
// Switched back to per vertex normals and smooth shading for terrain.
//
// Revision 1.13  1997/12/18 23:32:36  curt
// First stab at sky dome actually starting to look reasonable. :-)
//
// Revision 1.12  1997/12/17 23:13:47  curt
// Began working on rendering the sky.
//
// Revision 1.11  1997/12/15 23:55:01  curt
// Add xgl wrappers for debugging.
// Generate terrain normals on the fly.
//
// Revision 1.10  1997/12/12 21:41:28  curt
// More light/material property tweaking ... still a ways off.
//
// Revision 1.9  1997/12/12 19:52:57  curt
// Working on lightling and material properties.
//
// Revision 1.8  1997/12/10 01:19:51  curt
// Tweaks for verion 0.15 release.
//
// Revision 1.7  1997/12/08 22:51:17  curt
// Enhanced to handle ccw and cw tri-stripe winding.  This is a temporary
// admission of defeat.  I will eventually go back and get all the stripes
// wound the same way (ccw).
//
// Revision 1.6  1997/11/25 19:25:35  curt
// Changes to integrate Durk's moon/sun code updates + clean up.
//
// Revision 1.5  1997/11/15 18:16:39  curt
// minor tweaks.
//
// Revision 1.4  1997/11/14 00:26:49  curt
// Transform scenery coordinates earlier in pipeline when scenery is being
// created, not when it is being loaded.  Precalculate normals for each node
// as average of the normals of each containing polygon so Garoude shading is
// now supportable.
//
// Revision 1.3  1997/10/31 04:49:12  curt
// Tweaking vertex orders.
//
// Revision 1.2  1997/10/30 12:38:45  curt
// Working on new scenery subsystem.
//
// Revision 1.1  1997/10/28 21:14:54  curt
// Initial revision.