Aim :
To write a C program to implement SUTHERLAND – HODGEMANN polygon
clipping algorithm.
Algorithm:
Step 1: Start the program.
Step 2: Input Coordinates of all vertices of the polygon
Step 3: Input coordinates of the clipping window
Step 4: Consider the left edge of the window
Step 5: Compare the vertices of each edge of the polygon , individually with the clipping plane
Step 6: Save the resulting intersections and vertices in the new list of vertices according to four
possible relationships between the edge and the clipping boundary discussed
earlier
Step 7: Repeat the steps 4 and 5 for remaining edges of the clipping window. Each time the
resultant list of vertices is successively passed to process the next edge of the
clipping window
Step 8: Stop the Program.
PROGRAM:
#include
#include
#include
#include
#include
#define TRUE 1
#define FALSE 0
typedef unsigned int outcode;
outcode CompOutCode(float x,float y);
enum
{
TOP = 0x1,
BOTTOM = 0x2,
RIGHT = 0x4,
LEFT = 0x8
};
float xwmin,xwmax,ywmin,ywmax;
void clip(float x0,float y0,float x1,float y1)
{
outcode outcode0,outcode1,outcodeOut;
int accept = FALSE,done = FALSE;
outcode0 = CompOutCode(x0,y0);
outcode1 = CompOutCode(x1,y1);
do
{
if(!(outcode0|outcode1))
{
accept = TRUE;
done = TRUE;
}
else
if(outcode0 & outcode1)
done = TRUE;
else
{
float x,y;
outcodeOut = outcode0?outcode0:outcode1;
if(outcodeOut & TOP)
{
x = x0+(x1-x0)*(ywmax-y0)/(y1-y0);
y = ywmax;
}
else
if(outcodeOut & BOTTOM)
{
x = x0+(x1-x0)*(ywmin-y0)/(y1-y0);
y = ywmin;
}
else
if(outcodeOut & RIGHT)
{
y = y0+(y1-y0)*(xwmax-x0)/(x1-x0);
x = xwmax;
}
else
{
y = y0+(y1-y0)*(xwmin-x0)/(x1-x0);
x = xwmin;
}
if(outcodeOut==outcode0)
{
x0 = x;
y0 = y;
outcode0 = CompOutCode(x0,y0);
}
else
{
x1 = x;
y1 = y;
outcode1 = CompOutCode(x1,y1);
}
}
}
while(done==FALSE);
if(accept)
line(x0,y0,x1,y1);
outtextxy(150,20,"POLYGON AFTER CLIPPING");
rectangle(xwmin,ywmin,xwmax,ywmax);
}
outcode CompOutCode(float x,float y)
{
outcode code = 0;
if(y>ywmax)
code|=TOP;
else
if(y
code|=BOTTOM;
if(x>xwmax)
code|=RIGHT;
else
if(x
code|=LEFT;
return code;
}
void main( )
{
float x1,y1,x2,y2;
/* request auto detection */
int gdriver = DETECT, gmode, n,poly[14],i;
clrscr( );
printf("Enter the no of sides of polygon:");
scanf("%d",&n);
printf("\nEnter the coordinates of polygon\n");
for(i=0;i<2 font="" i="" n="" nbsp="">2>
{
scanf("%d",&poly[i]);
}
poly[2*n]=poly[0];
poly[2*n+1]=poly[1];
printf("Enter the rectangular coordinates of clipping window\n");
scanf("%f%f%f%f",&xwmin,&ywmin,&xwmax,&ywmax);
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "c:\\tc\\bgi");
outtextxy(150,20,"POLYGON BEFORE CLIPPING");
drawpoly(n+1,poly);
rectangle(xwmin,ywmin,xwmax,ywmax);
getch( );
cleardevice( );
for(i=0;i
clip(poly[2*i],poly[(2*i)+1],poly[(2*i)+2],poly[(2*i)+3]);
getch( );
restorecrtmode( );
}
OUTPUT:
Enter the no of sides of polygon:5
Enter the coordinates of polygon
50
50
200
100
350
350
80
200
40
80
Enter the rectangular coordinates of clipping window
150
150
300
300
POLYGON CLIPPING
RESULT:
Thus the above program has been executed and output is verified.
After clipping
Before clipping
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