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CohenSutherlandAlgorithm.c
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"Develop a OpenGL program to Clip 2D lines using Cohen-Sutherland
algorithm."
#include <stdio.h>
#include <stdbool.h>
#include <GL/glu.h>
#include <GL/glut.h>
double xmin = 50, ymin = 50, xmax = 100, ymax = 100;
double xvmin = 200, yvmin = 200, xvmax = 300, yvmax = 300;
const int LEFT = 1;
const int RIGHT = 2;
const int BOTTOM = 4;
const int TOP = 8;
int ComputeOutCode (double x, double y)
{
int code = 0;
if (y > ymax)
code |= TOP;
else if (y < ymin)
code |= BOTTOM;
if (x > xmax)
code |= RIGHT;
else if (x < xmin)
code |= LEFT;
return code;
}
void CohenSutherland(double x0, double y0, double x1, double y1)
{
bool accept = false, done = false;
int outcode0, outcode1, outcodeOut;
outcode0 = ComputeOutCode (x0, y0);
outcode1 = ComputeOutCode (x1, y1);
do
{
if ( ! (outcode0 | outcode1))
{
accept = true;
done = true;
}
else if (outcode0 & outcode1)
done = true;
else
{
double x, y;
double m = (y1 - y0) / (x1 - x0);
outcodeOut = outcode0 ? outcode0: outcode1;
if (outcodeOut & TOP)
{
x = x0 + (1/m) * (ymax - y0);
y = ymax;
}
else if (outcodeOut & BOTTOM)
{
x = x0 + (1/m) * (ymin - y0);
y = ymin;
}
else if (outcodeOut & RIGHT)
{
y = y0 + m * (xmax - x0);
x = xmax;
}
else
{
y = y0 + m * (xmin - x0);
x = xmin;
}
if (outcodeOut == outcode0)
{
x0 = x;
y0 = y;
outcode0 = ComputeOutCode (x0, y0);
}
else
{
x1 = x;
y1 = y;
outcode1 = ComputeOutCode (x1, y1);
}
}
}
while (!done);
if (accept)
{
double sx = (xvmax - xvmin) / (xmax - xmin);
double sy = (yvmax - yvmin) / (ymax - ymin);
double vx0 = xvmin + (x0 - xmin) * sx;
double vy0 = yvmin + (y0 - ymin) * sy;
double vx1 = xvmin + (x1 - xmin) * sx;
double vy1 = yvmin + (y1 - ymin) * sy;
glBegin(GL_LINE_LOOP);
glVertex2f (xvmin, yvmin);
glVertex2f (xvmax, yvmin);
glVertex2f (xvmax, yvmax);
glVertex2f (xvmin, yvmax);
glEnd();
glBegin(GL_LINES);
glVertex2d (vx0, vy0);
glVertex2d (vx1, vy1);
glEnd();
}
}
void display()
{
double x0 = 60, y0 = 20, x1 = 80, y1 = 120;
glClear (GL_COLOR_BUFFER_BIT);
glColor3f(1, 1, 1);
glBegin (GL_LINES);
glVertex2d (x0, y0);
glVertex2d (x1, y1);
glEnd ();
glBegin (GL_LINE_LOOP);
glVertex2f (xmin, ymin);
glVertex2f (xmax, ymin);
glVertex2f (xmax, ymax);
glVertex2f (xmin, ymax);
glEnd ();
CohenSutherland (x0, y0, x1, y1);
glFlush ();
}
void init()
{
glClearColor (0, 0, 0, 1);
gluOrtho2D (0, 500, 0, 500);
}
int main(int argc, char **argv)
{
glutInit (&argc,argv);
glutInitDisplayMode (GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (0, 0);
glutCreateWindow ("Cohen Sutherland Line Clipping Algorithm");
init();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}