Program that creats a 3D solid object using Rotational Sweep Representatiom Method

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

# define  f                 0.3
# define  projection_angle   45

void show_screen( );

void apply_rotation_along_y_axis(const int,const int,const int,const int);
void multiply_matrices(const float[4],const float[4][4],float[4]);

void draw_circle(const int,const int,const int);
void get_projected_point(int&,int&,int&);

void Line(const int,const int,const int,const int);

int main( )
{
int driver=VGA;
int mode=VGAHI;

initgraph(&driver,&mode,\"..\\\\Bgi\");

show_screen( );

int x=0;
int y=250;
int z=200;

setcolor(15);
draw_circle(x,y,z);

setcolor(15);
settextstyle(0,0,1);
outtextxy(50,415,\"*** Press any key to make a 3D solid object i.e. Tube.\");

getch( );

for(int angle=0;angle<=360;angle++)
apply_rotation_along_y_axis(x,y,z,angle);

getch( );
return 0;
}

//-------------------  apply_rotation_along_y_axis( )  ------------------//

void apply_rotation_along_y_axis(const int x,const int y,
const int z,const int theta)
{
int _x=x;
int _y=y;
int _z=z;

float angle=(theta*(M_PI/180));

float matrix_a[4]={_x,_y,_z,1};

float matrix_b[4][4]={
{ cos(angle),0,-sin(angle),0 } ,
{ 0,1,0,0 } ,
{ sin(angle),0,cos(angle),0 } ,
{ 0,0,0,1 }
};

float matrix_c[4]={0};

multiply_matrices(matrix_a,matrix_b,matrix_c);

_x=(int)(matrix_c[0]+0.5);
_y=(int)(matrix_c[1]+0.5);
_z=(int)(matrix_c[2]+0.5);

draw_circle(_x,_y,_z);
}

/************************************************************************/
//----------------------  multiply_matrices( )  ------------------------//
/************************************************************************/

void multiply_matrices(const float matrix_1[4],
const float matrix_2[4][4],float matrix_3[4])
{
for(int count_1=0;count_1<4;count_1++)
{
for(int count_2=0;count_2<4;count_2++)
matrix_3[count_1]+=
(matrix_1[count_2]*matrix_2[count_2][count_1]);
}
}

/************************************************************************/
//--------------------------  draw_circle( )  -------------------------//
/************************************************************************/

void draw_circle(const int x,const int y,const int z)
{
int _x=x;
int _y=y;
int _z=z;

get_projected_point(_x,_y,_z);

_x+=320;

setcolor(15);
circle(_x,_y,30);
}

/************************************************************************/
//---------------------  get_projected_point( )  -----------------------//
/************************************************************************/

void get_projected_point(int& x,int& y,int& z)
{
float fcos0=(f*cos(projection_angle*(M_PI/180)));
float fsin0=(f*sin(projection_angle*(M_PI/180)));

float Par_v[4][4]={
{1,0,0,0},
{0,1,0,0},
{fcos0,fsin0,0,0},
{0,0,0,1}
};

float xy[4]={x,y,z,1};
float new_xy[4]={0};

multiply_matrices(xy,Par_v,new_xy);

x=(int)(new_xy[0]+0.5);
y=(int)(new_xy[1]+0.5);
z=(int)(new_xy[2]+0.5);
}

//--------------------------  show_screen( )  ---------------------------//

void show_screen( )
{
setfillstyle(1,1);
bar(154,26,476,38);

settextstyle(0,0,1);
setcolor(15);
outtextxy(5,5,\"******************************************************************************\");
outtextxy(5,17,\"*-**************************************************************************-*\");
outtextxy(5,29,\"*----------------                                           -----------------*\");
outtextxy(5,41,\"*-**************************************************************************-*\");
outtextxy(5,53,\"*-**************************************************************************-*\");

setcolor(11);
outtextxy(162,29,\"Rotational Sweep Representation Method\");

setcolor(15);

for(int count=0;count<=30;count++)
outtextxy(5,(65+(count*12)),\"*-*                                                                        *-*\");

outtextxy(5,438,\"*-**************************************************************************-*\");
outtextxy(5,450,\"*-------------------------                          -------------------------*\");
outtextxy(5,462,\"******************************************************************************\");

setcolor(12);
outtextxy(229,450,\"Press any Key to exit.\");
}
```