Program to show a 3D object using Polygon-Mesh Representation

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


 # define Xc -0.3
 # define Yc  0.3
 # define Zc -1.0


 void show_screen( );

 void draw_3d_polygon(int [5][3],int [8][2],int [5][5]);
 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 vertices[5][3]={
                {245,325,75},      //  base front left
                {395,325,75},      //  base front right
                {395,325,-75},     //  base back right
                {245,325,-75},     //  base back left
                {320,125,0}        //  top
              };

       int edges[8][2]={
             // first is starting point vertex number
             // second is ending point vertex number
             {0,3} , {3,2} , {2,1} , {1,0} , {0,4} ,
             {3,4} , {2,4} , {1,4}
               };

       int surfaces[5][5]={
                 // First entry is number of edges
                 // Rest entries are edge numbers
                 {4,0,1,2,3}, {3,0,4,5} , {3,1,5,6} ,
                 {3,2,6,7} , {3,3,4,7}
              };

       for(int i=0;i<5;i++)
      get_projected_point(vertices[i][0],vertices[i][1],vertices[i][2]);

       setcolor(15);
     draw_3d_polygon(vertices,edges,surfaces);

       settextstyle(2,0,4);
     setcolor(11);
       outtextxy(300,355,\"S1\");
       outtextxy(260,270,\"S2\");
       outtextxy(310,250,\"S3\");
       outtextxy(370,280,\"S4\");
       outtextxy(310,317,\"S5\");

     setcolor(10);
       outtextxy(255,315,\"E1\");
       outtextxy(320,291,\"E2\");
       outtextxy(403,315,\"E3\");
       outtextxy(310,337,\"E4\");
       outtextxy(250,250,\"E5\");
       outtextxy(288,240,\"E6\");
       outtextxy(390,240,\"E7\");
       outtextxy(356,260,\"E8\");

     setcolor(14);
       outtextxy(212,344,\"V1\");
       outtextxy(255,293,\"V2\");
       outtextxy(420,293,\"V3\");
       outtextxy(370,350,\"V4\");
       outtextxy(320,115,\"V5\");

       getch( );
       closegraph( );
       return 0;
    }

 /************************************************************************/
 //-------------------------  draw_3d_polygon( )  -----------------------//
 /************************************************************************/

 void draw_3d_polygon(int vertices[5][3],int edges[8][2],int surfaces[5][5])
    {
       for(int i=0;i<5;i++)
      {
         for(int j=1;j<=surfaces[i][0];j++)
        {
           int x_1=vertices[edges[surfaces[i][j]][0]][0];
           int y_1=vertices[edges[surfaces[i][j]][0]][1];
           int x_2=vertices[edges[surfaces[i][j]][1]][0];
           int y_2=vertices[edges[surfaces[i][j]][1]][1];

           Line(x_1,y_1,x_2,y_2);
        }
      }
    }

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

 void get_projected_point(int& x,int& y,int& z)
    {
       float projection_matrix[4][4]={
                      { -Zc,0,0,0 },
                      { 0,-Zc,0,0 },
                      { Xc,Yc,0,1 },
                      { 0,0,0,-Zc }
                   };

       float matrix3d[4]={x,y,z,1};
       float matrix2d[4]={0,0,0,0};

       for(int count_1=0;count_1<4;count_1++)
      {
         for(int count_2=0;count_2<4;count_2++)
        matrix2d[count_1]+=
               (matrix3d[count_2]*projection_matrix[count_2][count_1]);
      }

       x=(int)(matrix2d[0]+0.5);
       y=(int)(matrix2d[1]+0.5);
       z=(int)(matrix2d[2]+0.5);
    }


 //--------------------------  Line( )  ------------------------//


 void Line(const int x_1,const int y_1,const int x_2,const int y_2)
    {
       int color=getcolor( );

       int x1=x_1;
       int y1=y_1;

       int x2=x_2;
       int y2=y_2;

       if(x_1>x_2)
      {
         x1=x_2;
         y1=y_2;

         x2=x_1;
         y2=y_1;
      }

       int dx=abs(x2-x1);
       int dy=abs(y2-y1);
       int inc_dec=((y2>=y1)?1:-1);

       if(dx>dy)
      {
         int two_dy=(2*dy);
         int two_dy_dx=(2*(dy-dx));
         int p=((2*dy)-dx);

         int x=x1;
         int y=y1;

         putpixel(x,y,color);

         while(x<x2)
        {
           x++;

           if(p<0)
              p+=two_dy;

           else
              {
             y+=inc_dec;
             p+=two_dy_dx;
              }

           putpixel(x,y,color);
        }
      }

       else
      {
         int two_dx=(2*dx);
         int two_dx_dy=(2*(dx-dy));
         int p=((2*dx)-dy);

         int x=x1;
         int y=y1;

         putpixel(x,y,color);

         while(y!=y2)
        {
           y+=inc_dec;

           if(p<0)
              p+=two_dx;

           else
              {
             x++;
             p+=two_dx_dy;
              }

           putpixel(x,y,color);
        }
      }
    }


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


 void show_screen( )
    {
       setfillstyle(1,1);
     bar(205,26,438,38);

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

     setcolor(11);
       outtextxy(214,29,\"Polygon-Mesh Representation\");

     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(227,450,\"  Press any key to exit \");
    }