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

Posted By: Easy Tutor     Category: C++ Programming     Views: 4057

## Code for Program to show a 3D object using Polygon-Mesh Representation in C++ Programming

``` # 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(constint,constint,constint,constint);

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(constint x_1,constint y_1,constint x_2,constint 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 ");
}

```
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