/* File GLOBE.C: Terrestrial Globe - HGC/EGA version */

#include <math.h>
#include <conio.h>
#include <graphics.h>

typedef enum {false, true} boolean;

void graph(double y, double z, int *plotted);
void rotate3d(double xr, double yr, double zr, double *px, double *py, double *pz);

#define LATITUTE 37.29     // Áö±¸º» Áß¾ÓÁ¡ÀÇ À§µµ¿Í °æµµ(º¯°æ °¡´É)
#define LONGITUTE 127.04   // ÀÌ °ª ÀÌ¿ÜÀÇ ¼öÄ¡´Â ¼Õ´ëÁö ¸» °Í
				/*      |z        */
#define RADIUS 200.             /*      |         */
#define ZROTATE -LONGITUTE      /*    p/|   */
#define YROTATE -LATITUTE       /*     |+------ y */
#define XROTATE 22.5            /*     /-/        */
#define INTERVAL 15.            /*    /  fi       */
				/*   x            */
int main(void)
{
    int graphdrive = DETECT, graphmode;
    int plotted;
    double x, y, z;
    double p, fi;
    double zr, yr, xr;

    initgraph(&graphdrive, &graphmode, "");

    xr = XROTATE * M_PI / 180.;
    yr = YROTATE * M_PI / 180.;
    zr = ZROTATE * M_PI / 180.;
    circle(getmaxx() / 2, getmaxy() / 2, RADIUS);
    circle(getmaxx() / 2, getmaxy() / 2, 1);

    /* Latitute */

    for (p = M_PI_2; p > -M_PI_2; p -= INTERVAL * M_PI / 180.) {
        plotted = false;
	if (fabs(p - 0.) < 1.e-5)
            setlinestyle(SOLID_LINE, 0, THICK_WIDTH);
        else setlinestyle(SOLID_LINE, 0, NORM_WIDTH);
        for (fi = 0.; fi <= 2. * M_PI; fi += M_PI / 24.) {
            x = RADIUS * cos(p) * cos(fi);
	    y = RADIUS * cos(p) * sin(fi);
            z = RADIUS * sin(p);
            rotate3d(xr, yr, zr, &x, &y, &z);
            if (x < 0.) plotted = false;
            else graph(y, z, &plotted);
        }
    }

    /* Longitute */

    for (fi = 0.; fi < M_PI; fi += INTERVAL * M_PI / 180.) {
        plotted = false;
        if (fi == 0.) setlinestyle(SOLID_LINE, 0, THICK_WIDTH);
        else setlinestyle(SOLID_LINE, 0, NORM_WIDTH);
        for (p = 0.; p <= 2. * M_PI; p += M_PI / 24.) {
       x = RADIUS * cos(p) * cos(fi);
            y = RADIUS * cos(p) * sin(fi);
            z = RADIUS * sin(p);
            rotate3d(xr, yr, zr, &x, &y, &z);
            if (x < 0.) plotted = false;
	    else graph(y, z, &plotted);
        }
    }

    getch();
    closegraph();

    return(0);
}

/* Rotation order :  z axis -> y axis -> x axis */

void rotate3d(double xr, double yr, double zr, double *px, double *py, double *pz)
{
    double x = *px, y = *py, z = *pz;
    double x1, y1, z1, x2, y2, z2, x3, y3, z3;

    x1 = x * cos(zr) - y * sin(zr);
    y1 = x * sin(zr) + y * cos(zr);
    z1 = z;

    x2 = x1 * cos(yr) - z1 * sin(yr);
    y2 = y1;
    z2 = x1 * sin(yr) + z1 * cos(yr);

    x3 = x2;
    y3 = y2 * cos(xr) - z2 * sin(xr);
    z3 = y2 * sin(xr) + z2 * cos(xr);

    *px = x3;
    *py = y3;
    *pz = z3;
}

void graph(double y, double z, int *plotted)
{
    int xx, yy, xasp, yasp;

    getaspectratio(&xasp, &yasp);
    xx = getmaxx() / 2 + (int)y;
    yy = getmaxy() / 2 - (int)(z * xasp / yasp);

    if (*plotted == false) moveto(xx, yy);
    else lineto(xx, yy);
    *plotted = true;
}