Changes due to updates in fgstream.

[flightgear.git] / DEM / dem.cxx

// -*- Mode: C++ -*-
//
// dem.c -- DEM management class
//
// Written by Curtis Olson, started March 1998.
//
// Copyright (C) 1998  Curtis L. Olson  - curt@me.umn.edu
//
// 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

#include <ctype.h>    // isspace()
#include <stdlib.h>   // atoi()
#include <math.h>     // rint()
#include <stdio.h>
#include <string.h>
#include <sys/stat.h> // stat()
#include <errno.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>   // stat()
#endif
#include <string>

// #include <zlib/zlib.h>
#include <Misc/fgstream.hxx>
#include <Misc/strutils.hxx>
#include <Include/compiler.h>
FG_USING_NAMESPACE(std);

#include "dem.hxx"
#include "leastsqs.hxx"

#include <Include/fg_constants.h>


#define MAX_EX_NODES 10000

#if 0
#ifdef WIN32
# ifdef __BORLANDC__
#  include <dir.h>
#  define MKDIR(a) mkdir(a)
# else
#  define MKDIR(a) mkdir(a,S_IRWXU)  // I am just guessing at this flag (NHV)
# endif // __BORLANDC__
#endif // WIN32
#endif //0


fgDEM::fgDEM( void ) {
    // printf("class fgDEM CONstructor called.\n");
    dem_data = new float[DEM_SIZE_1][DEM_SIZE_1];
    output_data = new float[DEM_SIZE_1][DEM_SIZE_1];
}


#if 0
#ifdef WIN32

// return the file path name ( foo/bar/file.ext = foo/bar )
static void extract_path ( const char *in, char *base) {
    int len, i;
    
    len = strlen (in);
    strcpy (base, in);

    i = len - 1;
    while ( (i >= 0) && (in[i] != '/') ) {
        i--;
    }

    base[i] = '\0';
}


// Make a subdirectory
static int my_mkdir (const char *dir) {
    struct stat stat_buf;
    int result;

    printf ("mk_dir() ");

    result = stat (dir, &stat_buf);

    if (result != 0) {
        MKDIR (dir);
        result = stat (dir, &stat_buf);
        if (result != 0) {
            printf ("problem creating %s\n", dir);
        } else {
            printf ("%s created\n", dir);
        }
    } else {
        printf ("%s already exists\n", dir);
    }

    return (result);
}

#endif // WIN32
#endif //0


// open a DEM file
int fgDEM::open ( const string& file ) {
    // open input file (or read from stdin)
    if ( file ==  "-" ) {
        printf("Loading DEM data file: stdin\n");
        // fd = stdin;
        // fd = gzdopen(STDIN_FILENO, "r");
        printf("Not yet ported ...\n");
        return 0;
    } else {
        in = new fg_gzifstream( file );
        if ( !(*in) ) {
            cout << "Cannot open " << file << endl;
            return 0;
        }
        cout << "Loading DEM data file: " << file << endl;
    }

    return 1;
}


// close a DEM file
int fgDEM::close () {
    // the fg_gzifstream doesn't seem to have a close()

    delete in;

    return 1;
}


// return next token from input stream
string fgDEM::next_token() {
    string token;

    *in >> token;

    // cout << "    returning " + token + "\n";

    return token;
}


// return next integer from input stream
int fgDEM::next_int() {
    int result;
    
    *in >> result;

    return result;
}


// return next double from input stream
double fgDEM::next_double() {
    double result;

    *in >> result;

    return result;
}


// return next exponential num from input stream
double fgDEM::next_exp() {
    string token;
    double mantissa;
    int exp, acc;
    int i;

    token = next_token();

#if 1
    const char* p = token.c_str();
    char buf[64];
    char* bp = buf;
    
    for ( ; *p != 0; ++p )
    {
        if ( *p == 'D' )
            *bp++ = 'E';
        else
            *bp++ = *p;
    }
    *bp = 0;
    return ::atof( buf );
#else
    sscanf(token.c_str(), "%lfD%d", &mantissa, &exp);

    // cout << "    Mantissa = " << mantissa << "  Exp = " << exp << "\n";

    acc = 1;
    if ( exp > 0 ) {
        for ( i = 1; i <= exp; i++ ) {
            acc *= 10;
        }
    } else if ( exp < 0 ) {
        for ( i = -1; i >= exp; i-- ) {
            acc /= 10;
        }
    }

    return( (int)rint(mantissa * (double)acc) );
#endif
}


// read and parse DEM "A" record
int fgDEM::read_a_record() {
    int i, inum;
    double dnum;
    string name, token;
    char c;
    char *ptr;

    // get the name field (144 characters)
    for ( i = 0; i < 144; i++ ) {
        in->get(c);
        name += c;
    }
  
    // clean off the trailing whitespace
    name = trim(name);
    cout << "    Quad name field: " << name << endl;

    // DEM level code, 3 reflects processing by DMA
    inum = next_int();
    cout << "    DEM level code = " << inum << "\n";

    if ( inum > 3 ) {
        return 0;
    }

    // Pattern code, 1 indicates a regular elevation pattern
    inum = next_int();
    cout << "    Pattern code = " << inum << "\n";

    // Planimetric reference system code, 0 indicates geographic
    // coordinate system.
    inum = next_int();
    cout << "    Planimetric reference code = " << inum << "\n";

    // Zone code
    inum = next_int();
    cout << "    Zone code = " << inum << "\n";

    // Map projection parameters (ignored)
    for ( i = 0; i < 15; i++ ) {
        dnum = next_exp();
        // printf("%d: %f\n",i,dnum);
    }

    // Units code, 3 represents arc-seconds as the unit of measure for
    // ground planimetric coordinates throughout the file.
    inum = next_int();
    if ( inum != 3 ) {
        cout << "    Unknown (X,Y) units code = " << inum << "!\n";
        exit(-1);
    }

    // Units code; 2 represents meters as the unit of measure for
    // elevation coordinates throughout the file.
    inum = next_int();
    if ( inum != 2 ) {
        cout << "    Unknown (Z) units code = " << inum << "!\n";
        exit(-1);
    }

    // Number (n) of sides in the polygon which defines the coverage of
    // the DEM file (usually equal to 4).
    inum = next_int();
    if ( inum != 4 ) {
        cout << "    Unknown polygon dimension = " << inum << "!\n";
        exit(-1);
    }

    // Ground coordinates of bounding box in arc-seconds
    dem_x1 = originx = next_exp();
    dem_y1 = originy = next_exp();
    cout << "    Origin = (" << originx << "," << originy << ")\n";

    dem_x2 = next_exp();
    dem_y2 = next_exp();

    dem_x3 = next_exp();
    dem_y3 = next_exp();

    dem_x4 = next_exp();
    dem_y4 = next_exp();

    // Minimum/maximum elevations in meters
    dem_z1 = next_exp();
    dem_z2 = next_exp();
    cout << "    Elevation range " << dem_z1 << " to " << dem_z2 << "\n";

    // Counterclockwise angle from the primary axis of ground
    // planimetric referenced to the primary axis of the DEM local
    // reference system.
    token = next_token();

    // Accuracy code; 0 indicates that a record of accuracy does not
    // exist and that no record type C will follow.

    // DEM spacial resolution.  Usually (3,3,1) (3,6,1) or (3,9,1)
    // depending on latitude

    // I will eventually have to do something with this for data at
    // higher latitudes */
    token = next_token();
    cout << "    accuracy & spacial resolution string = " << token << endl;
    i = token.length();
    cout << "    length = " << i << "\n";

#if 1
    inum = atoi( token.substr( 0, i - 36 ) );
    row_step = atof( token.substr( i - 36, 12 ) );
    col_step = atof( token.substr( i - 24, 12 ) );
    //token.substr( 25, 12 )
#else
    ptr = token.c_str() + i - 12;
    cout << "    last field = " << ptr << " = " << atof(ptr) << "\n";
    ptr[0] = '\0';

    ptr = ptr - 12;
    col_step = atof(ptr);
    cout << "    last field = " << ptr << " = " << col_step << "\n";
    ptr[0] = '\0';

    ptr = ptr - 12;
    row_step = atof(ptr);
    cout << "    last field = " << ptr << " = " << row_step << "\n";
    ptr[0] = '\0';

    // accuracy code = atod(token)
    ptr = ptr - 12;
    inum = atoi(ptr);
#endif
    cout << "    Accuracy code = " << inum << "\n";

    cout << "    column step = " << col_step << 
        "  row step = " << row_step << "\n";

    // dimension of arrays to follow (1)
    token = next_token();

    // number of profiles
    dem_num_profiles = cols = next_int();
    cout << "    Expecting " << dem_num_profiles << " profiles\n";

    return 1;
}


// read and parse DEM "B" record
void fgDEM::read_b_record( ) {
    string token;
    int i;

    // row / column id of this profile
    prof_row = next_int();
    prof_col = next_int();
    // printf("col id = %d  row id = %d\n", prof_col, prof_row);

    // Number of columns and rows (elevations) in this profile
    prof_num_rows = rows = next_int();
    prof_num_cols = next_int();
    // printf("    profile num rows = %d\n", prof_num_rows);

    // Ground planimetric coordinates (arc-seconds) of the first
    // elevation in the profile
    prof_x1 = next_exp();
    prof_y1 = next_exp();
    // printf("    Starting at %.2f %.2f\n", prof_x1, prof_y1);

    // Elevation of local datum for the profile.  Always zero for
    // 1-degree DEM, the reference is mean sea level.
    token = next_token();

    // Minimum and maximum elevations for the profile.
    token = next_token();
    token = next_token();

    // One (usually) dimensional array (prof_num_cols,1) of elevations
    for ( i = 0; i < prof_num_rows; i++ ) {
        prof_data = next_int();
        dem_data[cur_col][i] = (float)prof_data;
    }
}


// parse dem file
int fgDEM::parse( ) {
    int i;

    cur_col = 0;

    if ( !read_a_record() ) {
        return(0);
    }

    for ( i = 0; i < dem_num_profiles; i++ ) {
        // printf("Ready to read next b record\n");
        read_b_record();
        cur_col++;

        if ( cur_col % 100 == 0 ) {
            cout << "    loaded " << cur_col << " profiles of data\n";
        }
    }

    cout << "    Done parsing\n";

    return 1;
}


// return the current altitude based on mesh data.  We should rewrite
// this to interpolate exact values, but for now this is good enough
double fgDEM::interpolate_altitude( double lon, double lat ) {
    // we expect incoming (lon,lat) to be in arcsec for now

    double xlocal, ylocal, dx, dy, zA, zB, elev;
    int x1, x2, x3, y1, y2, y3;
    float z1, z2, z3;
    int xindex, yindex;

    /* determine if we are in the lower triangle or the upper triangle 
       ______
       |   /|
       |  / |
       | /  |
       |/   |
       ------

       then calculate our end points
     */

    xlocal = (lon - originx) / col_step;
    ylocal = (lat - originy) / row_step;

    xindex = (int)(xlocal);
    yindex = (int)(ylocal);

    // printf("xindex = %d  yindex = %d\n", xindex, yindex);

    if ( xindex + 1 == cols ) {
        xindex--;
    }

    if ( yindex + 1 == rows ) {
        yindex--;
    }

    if ( (xindex < 0) || (xindex + 1 >= cols) ||
         (yindex < 0) || (yindex + 1 >= rows) ) {
        return(-9999);
    }

    dx = xlocal - xindex;
    dy = ylocal - yindex;

    if ( dx > dy ) {
        // lower triangle
        // printf("  Lower triangle\n");

        x1 = xindex; 
        y1 = yindex; 
        z1 = dem_data[x1][y1];

        x2 = xindex + 1; 
        y2 = yindex; 
        z2 = dem_data[x2][y2];
                                  
        x3 = xindex + 1; 
        y3 = yindex + 1; 
        z3 = dem_data[x3][y3];

        // printf("  dx = %.2f  dy = %.2f\n", dx, dy);
        // printf("  (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
        // printf("  (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
        // printf("  (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);

        zA = dx * (z2 - z1) + z1;
        zB = dx * (z3 - z1) + z1;
        
        // printf("  zA = %.2f  zB = %.2f\n", zA, zB);

        if ( dx > FG_EPSILON ) {
            elev = dy * (zB - zA) / dx + zA;
        } else {
            elev = zA;
        }
    } else {
        // upper triangle
        // printf("  Upper triangle\n");

        x1 = xindex; 
        y1 = yindex; 
        z1 = dem_data[x1][y1];

        x2 = xindex; 
        y2 = yindex + 1; 
        z2 = dem_data[x2][y2];
                                  
        x3 = xindex + 1; 
        y3 = yindex + 1; 
        z3 = dem_data[x3][y3];

        // printf("  dx = %.2f  dy = %.2f\n", dx, dy);
        // printf("  (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
        // printf("  (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
        // printf("  (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);
 
        zA = dy * (z2 - z1) + z1;
        zB = dy * (z3 - z1) + z1;
        
        // printf("  zA = %.2f  zB = %.2f\n", zA, zB );
        // printf("  xB - xA = %.2f\n", col_step * dy / row_step);

        if ( dy > FG_EPSILON ) {
            elev = dx * (zB - zA) / dy    + zA;
        } else {
            elev = zA;
        }
    }

    return(elev);
}


// Use least squares to fit a simpler data set to dem data
void fgDEM::fit( double error, fgBUCKET *p ) {
    double x[DEM_SIZE_1], y[DEM_SIZE_1];
    double m, b, ave_error, max_error;
    double cury, lasty;
    int n, row, start, end;
    int colmin, colmax, rowmin, rowmax;
    bool good_fit;
    // FILE *dem, *fit, *fit1;

    printf("Initializing output mesh structure\n");
    outputmesh_init();

    // determine dimensions
    colmin = p->x * ( (cols - 1) / 8);
    colmax = colmin + ( (cols - 1) / 8);
    rowmin = p->y * ( (rows - 1) / 8);
    rowmax = rowmin + ( (rows - 1) / 8);
    printf("Fitting region = %d,%d to %d,%d\n", colmin, rowmin, colmax, rowmax);
    
    // include the corners explicitly
    outputmesh_set_pt(colmin, rowmin, dem_data[colmin][rowmin]);
    outputmesh_set_pt(colmin, rowmax, dem_data[colmin][rowmax]);
    outputmesh_set_pt(colmax, rowmax, dem_data[colmax][rowmax]);
    outputmesh_set_pt(colmax, rowmin, dem_data[colmax][rowmin]);

    printf("Beginning best fit procedure\n");

    for ( row = rowmin; row <= rowmax; row++ ) {
        // fit  = fopen("fit.dat",  "w");
        // fit1 = fopen("fit1.dat", "w");

        start = colmin;

        // printf("    fitting row = %d\n", row);

        while ( start < colmax ) {
            end = start + 1;
            good_fit = true;

            x[(end - start) - 1] = 0.0 + ( start * col_step );
            y[(end - start) - 1] = dem_data[start][row];

            while ( (end <= colmax) && good_fit ) {
                n = (end - start) + 1;
                // printf("Least square of first %d points\n", n);
                x[end - start] = 0.0 + ( end * col_step );
                y[end - start] = dem_data[end][row];
                least_squares(x, y, n, &m, &b);
                ave_error = least_squares_error(x, y, n, m, b);
                max_error = least_squares_max_error(x, y, n, m, b);

                /*
                printf("%d - %d  ave error = %.2f  max error = %.2f  y = %.2f*x + %.2f\n", 
                start, end, ave_error, max_error, m, b);
                
                f = fopen("gnuplot.dat", "w");
                for ( j = 0; j <= end; j++) {
                    fprintf(f, "%.2f %.2f\n", 0.0 + ( j * col_step ), 
                            dem_data[row][j]);
                }
                for ( j = start; j <= end; j++) {
                    fprintf(f, "%.2f %.2f\n", 0.0 + ( j * col_step ), 
                            dem_data[row][j]);
                }
                fclose(f);

                printf("Please hit return: "); gets(junk);
                */

                if ( max_error > error ) {
                    good_fit = false;
                }
                
                end++;
            }

            if ( !good_fit ) {
                // error exceeded the threshold, back up
                end -= 2;  // back "end" up to the last good enough fit
                n--;       // back "n" up appropriately too
            } else {
                // we popped out of the above loop while still within
                // the error threshold, so we must be at the end of
                // the data set
                end--;
            }
            
            least_squares(x, y, n, &m, &b);
            ave_error = least_squares_error(x, y, n, m, b);
            max_error = least_squares_max_error(x, y, n, m, b);

            /*
            printf("\n");
            printf("%d - %d  ave error = %.2f  max error = %.2f  y = %.2f*x + %.2f\n", 
                   start, end, ave_error, max_error, m, b);
            printf("\n");

            fprintf(fit1, "%.2f %.2f\n", x[0], m * x[0] + b);
            fprintf(fit1, "%.2f %.2f\n", x[end-start], m * x[end-start] + b);
            */

            if ( start > colmin ) {
                // skip this for the first line segment
                cury = m * x[0] + b;
                outputmesh_set_pt(start, row, (lasty + cury) / 2);
                // fprintf(fit, "%.2f %.2f\n", x[0], (lasty + cury) / 2);
            }

            lasty = m * x[end-start] + b;
            start = end;
        }

        /*
        fclose(fit);
        fclose(fit1);

        dem = fopen("gnuplot.dat", "w");
        for ( j = 0; j < DEM_SIZE_1; j++) {
            fprintf(dem, "%.2f %.2f\n", 0.0 + ( j * col_step ), 
                    dem_data[j][row]);
        } 
        fclose(dem);
        */

        // NOTICE, this is for testing only.  This instance of
        // output_nodes should be removed.  It should be called only
        // once at the end once all the nodes have been generated.
        // newmesh_output_nodes(&nm, "mesh.node");
        // printf("Please hit return: "); gets(junk);
    }

    // outputmesh_output_nodes(fg_root, p);
}


// Initialize output mesh structure
void fgDEM::outputmesh_init( void ) {
    int i, j;
    
    for ( j = 0; j < DEM_SIZE_1; j++ ) {
        for ( i = 0; i < DEM_SIZE_1; i++ ) {
            output_data[i][j] = -9999.0;
        }
    }
}


// Get the value of a mesh node
double fgDEM::outputmesh_get_pt( int i, int j ) {
    return ( output_data[i][j] );
}


// Set the value of a mesh node
void fgDEM::outputmesh_set_pt( int i, int j, double value ) {
    // printf("Setting data[%d][%d] = %.2f\n", i, j, value);
   output_data[i][j] = value;
}


// Write out a node file that can be used by the "triangle" program.
// Check for an optional "index.node.ex" file in case there is a .poly
// file to go along with this node file.  Include these nodes first
// since they are referenced by position from the .poly file.
void fgDEM::outputmesh_output_nodes( const string& fg_root, fgBUCKET *p ) {
    double exnodes[MAX_EX_NODES][3];
    struct stat stat_buf;
    string dir;
    char base_path[256], file[256], exfile[256];
#ifdef WIN32
    char tmp_path[256];
#endif
    string command;
    FILE *fd;
    long int index;
    int colmin, colmax, rowmin, rowmax;
    int i, j, count, excount, result;

    // determine dimensions
    colmin = p->x * ( (cols - 1) / 8);
    colmax = colmin + ( (cols - 1) / 8);
    rowmin = p->y * ( (rows - 1) / 8);
    rowmax = rowmin + ( (rows - 1) / 8);
    cout << "  dumping region = " << colmin << "," << rowmin << " to " <<
        colmax << "," << rowmax << "\n";

    // generate the base directory
    fgBucketGenBasePath(p, base_path);
    cout << "fg_root = " << fg_root << "  Base Path = " << base_path << endl;
    dir = fg_root + "/Scenery/" + base_path;
    cout << "Dir = " << dir << endl;
    
    // stat() directory and create if needed
    errno = 0;
    result = stat(dir.c_str(), &stat_buf);
    if ( result != 0 && errno == ENOENT ) {
        cout << "Creating directory\n";

// #ifndef WIN32

        command = "mkdir -p " + dir + "\n";
        system( command.c_str() );

#if 0
// #else // WIN32

        // Cygwin crashes when trying to output to node file
        // explicitly making directory structure seems OK on Win95

        extract_path (base_path, tmp_path);

        dir = fg_root + "/Scenery";
        if (my_mkdir ( dir.c_str() )) { exit (-1); }

        dir = fg_root + "/Scenery/" + tmp_path;
        if (my_mkdir ( dir.c_str() )) { exit (-1); }

        dir = fg_root + "/Scenery/" + base_path;
        if (my_mkdir ( dir.c_str() )) { exit (-1); }

// #endif // WIN32
#endif //0

    } else {
        // assume directory exists
    }

    // get index and generate output file name
    index = fgBucketGenIndex(p);
    sprintf(file, "%s/%ld.node", dir.c_str(), index);

    // get (optional) extra node file name (in case there is matching
    // .poly file.
    strcpy(exfile, file);
    strcat(exfile, ".ex");

    // load extra nodes if they exist
    excount = 0;
    if ( (fd = fopen(exfile, "r")) != NULL ) {
        int junki;
        fscanf(fd, "%d %d %d %d", &excount, &junki, &junki, &junki);

        if ( excount > MAX_EX_NODES - 1 ) {
            printf("Error, too many 'extra' nodes, increase array size\n");
            exit(-1);
        } else {
            printf("    Expecting %d 'extra' nodes\n", excount);
        }

        for ( i = 1; i <= excount; i++ ) {
            fscanf(fd, "%d %lf %lf %lf\n", &junki, 
                   &exnodes[i][0], &exnodes[i][1], &exnodes[i][2]);
            printf("(extra) %d %.2f %.2f %.2f\n", 
                    i, exnodes[i][0], exnodes[i][1], exnodes[i][2]);
        }
        fclose(fd);
    }

    printf("Creating node file:  %s\n", file);
    fd = fopen(file, "w");

    // first count regular nodes to generate header
    count = 0;
    for ( j = rowmin; j <= rowmax; j++ ) {
        for ( i = colmin; i <= colmax; i++ ) {
            if ( output_data[i][j] > -9000.0 ) {
                count++;
            }
        }
        // printf("    count = %d\n", count);
    }
    fprintf(fd, "%d 2 1 0\n", count + excount);

    // now write out extra node data
    for ( i = 1; i <= excount; i++ ) {
        fprintf(fd, "%d %.2f %.2f %.2f\n", 
                i, exnodes[i][0], exnodes[i][1], exnodes[i][2]);
    }

    // write out actual node data
    count = excount + 1;
    for ( j = rowmin; j <= rowmax; j++ ) {
        for ( i = colmin; i <= colmax; i++ ) {
            if ( output_data[i][j] > -9000.0 ) {
                fprintf(fd, "%d %.2f %.2f %.2f\n", 
                        count++, 
                        originx + (double)i * col_step, 
                        originy + (double)j * row_step,
                        output_data[i][j]);
            }
        }
        // printf("    count = %d\n", count);
    }

    fclose(fd);
}


fgDEM::~fgDEM( void ) {
    // printf("class fgDEM DEstructor called.\n");
    delete [] dem_data;
    delete [] output_data;
}


// $Log$
// Revision 1.21  1998/11/06 14:04:32  curt
// Changes due to updates in fgstream.
//
// Revision 1.20  1998/10/28 19:38:20  curt
// Elliminate some unnecessary win32 specific stuff (by Norman Vine)
//
// Revision 1.19  1998/10/22 21:59:19  curt
// Fixed a couple subtle bugs that resulted from some of my c++ conversions.
// One bug could cause a segfault on certain input, and the other bug could
// cause the whole procedure to go balistic and generate huge files (also only
// on rare input combinations.)
//
// Revision 1.18  1998/10/18 01:17:09  curt
// Point3D tweaks.
//
// Revision 1.17  1998/10/16 19:08:12  curt
// Portability updates from Bernie Bright.
//
// Revision 1.16  1998/10/02 21:41:39  curt
// Fixes for win32.
//
// Revision 1.15  1998/09/21 20:53:59  curt
// minor tweaks to clean a few additional things up after the rewrite.
//
// Revision 1.14  1998/09/19 17:59:45  curt
// Use c++ streams (fg_gzifstream).  Also converted many character arrays to
// the string class.
//
// Revision 1.13  1998/09/09 16:24:04  curt
// Fixed a bug in the handling of exclude files which was causing
// a crash by calling fclose() on an invalid file handle.
//
// Revision 1.12  1998/08/24 20:03:31  curt
// Eliminated a possible memory overrun error.
// Use the proper free() rather than the incorrect delete().
//
// Revision 1.11  1998/07/20 12:46:11  curt
// When outputing to a .node file, first check for an optional
// "index.node.ex" file in case there is a .poly file to go along with this
// node file.  Include these nodes first since they are referenced by position
// from the .poly file.  This is my first pass at adding an area "cutout"
// feature to the terrain generation pipeline.
//
// Revision 1.10  1998/07/13 20:58:02  curt
// .
//
// Revision 1.9  1998/07/13 15:29:49  curt
// Added #ifdef HAVE_CONFIG_H
//
// Revision 1.8  1998/07/04 00:47:18  curt
// typedef'd struct fgBUCKET.
//
// Revision 1.7  1998/06/05 18:14:39  curt
// Abort out early when reading the "A" record if it doesn't look like
// a proper DEM file.
//
// Revision 1.6  1998/05/02 01:49:21  curt
// Fixed a bug where the wrong variable was being initialized.
//
// Revision 1.5  1998/04/25 15:00:32  curt
// Changed "r" to "rb" in gzopen() options.  This fixes bad behavior in win32.
//
// Revision 1.4  1998/04/22 13:14:46  curt
// Fixed a bug in zlib usage.
//
// Revision 1.3  1998/04/18 03:53:05  curt
// Added zlib support.
//
// Revision 1.2  1998/04/14 02:43:27  curt
// Used "new" to auto-allocate large DEM parsing arrays in class constructor.
//
// Revision 1.1  1998/04/08 22:57:22  curt
// Adopted Gnu automake/autoconf system.
//
// Revision 1.3  1998/04/06 21:09:41  curt
// Additional win32 support.
// Fixed a bad bug in dem file parsing that was causing the output to be
// flipped about x = y.
//
// Revision 1.2  1998/03/23 20:35:41  curt
// Updated to use FG_EPSILON
//
// Revision 1.1  1998/03/19 02:54:47  curt
// Reorganized into a class lib called fgDEM.
//
// Revision 1.1  1998/03/19 01:46:28  curt
// Initial revision.
//