// Program for calculation of an apple shaped surface，Jan. 19, 2011.



// file name: apple_surface.c



#include< stdio.h>

#include< math.h>



void main(void)

{

	double a,pi;// a is a constant and pi is the Pi.

	double b;// a compression constant towards y direction

	double p, q;
// compression coefficients towards x and y directions respectively

	double t,dt;
// an intermediate variable and its increment [radian] of Cardioid before the conversion

	double R;// radius of Cardioid before the conversion

	double fi,fimax,dfi;
// the phase angle in (z, x) plane, its maximum value and its increment [radian]

	double tmin,tmax;
// the minimum and maximum values of the intermediate variable t [radian]

	int i,imax;

	double xx[20001],yy[20001],zz[20001];
// Take care of the upper limit of storage memory capacitance.



	FILE *fp;



// setting of the constant

	pi=3.14159265;

	a=1.0;// 1.0

	b=1.2;// 1.0

	p=0.15;// 0.15

	q=0.08;// 0.08



// setting of the other parameters

	tmin=-pi/2;

	tmax=pi/2;

	dt=(tmax-tmin)/100;// plotting interval of t

	fimax=2*pi;

	dfi=fimax/36;// plotting interval of fi



// execution of calculation

	i=0;

	for(t=tmin;t<=tmax+dt;t=t+dt)

    {

		R=a*(1-sin(t));

		for(fi=0;fi<=fimax+dfi;fi=fi+dfi)

		{

			i++;

			zz[i]=(R*cos(t)*exp(-p*(t-pi/2)*(t-pi/2)))*cos(fi);

			xx[i]=(R*cos(t)*exp(-p*(t-pi/2)*(t-pi/2)))*sin(fi);

			yy[i]=b*R*sin(t)*exp(-q*(t-pi/2)*(t-pi/2));



		printf("i=%d,x=%f,y=%f,z=%f\n",i,xx[i],yy[i],zz[i]);

		}

	}

	imax=i;



// writing the calculated coordinates data of the apple shaped surface into a textfile

	fp=fopen("apple_surface.txt","w");

	if(fp==NULL)

		{

		printf("FILE OPEN ERROR\n");

		}

	else

		{

		for(i=1;i<=imax;i++)

			{

			fprintf(fp,"%f,%f,%f\n",xx[i],yy[i],zz[i]);

			}

		fflush(fp);

		fclose(fp);

		}

	printf("end\n");

}// the end of the program