// C++ program to implement Cohen Sutherland algorithm
// for line clipping.
#include <iostream>
#include <GL/glut.h>
using namespace std;
// Defining region codes
const int INSIDE = 0; // 0000
const int LEFT = 1; // 0001
const int RIGHT = 2; // 0010
const int BOTTOM = 4; // 0100
const int TOP = 8; // 1000
// Defining x_max, y_max and x_min, y_min for
// clipping rectangle. Since diagonal points are
// enough to define a rectangle
const int x_max = 100;
const int y_max = 100;
const int x_min = 40;
const int y_min = 40;
int x1,x2,y1,y2;
// Function to compute region code for a point(x, y)
int computeCode(double x, double y)
{
// initialized as being inside
int code = INSIDE;
if (x < x_min) // to the left of rectangle
code |= LEFT;
else if (x > x_max) // to the right of rectangle
code |= RIGHT;
if (y < y_min) // below the rectangle
code |= BOTTOM;
else if (y > y_max) // above the rectangle
code |= TOP;
return code;
}
// Implementing Cohen-Sutherland algorithm
// Clipping a line from P1 = (x2, y2) to P2 = (x2, y2)
void cohenSutherlandClip(double x1, double y1,double x2, double y2)
{
// Compute region codes for P1, P2
int code1 = computeCode(x1, y1);
int code2 = computeCode(x2, y2);
// Initialize line as outside the rectangular window
bool accept = false;
while (true)
{
if ((code1 == 0) && (code2 == 0))
{
// If both endpoints lie within rectangle
accept = true;
break;
}
else if (code1 & code2)
{
// If both endpoints are outside rectangle,
// in same region
break;
}
}
if (accept)
{
cout <<"Line accepted from (" << x1 << ", "
<< y1 << " to "<< x2 << ", " << y2 << ") because its completely VISIBLE" << endl;
// Here the user can add code to display the rectangle
// along with the accepted (portion of) lines
}
else
cout <<"Line rejected from (" << x1 << ", "
<< y1 << " to "<< x2 << ", " << y2 << ") because its completely INVISIBLE" << endl;
}
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0,1.0,0.0);
glBegin(GL_LINES);
glVertex2i(40,100);
glVertex2i(40,10);
glVertex2i(100,100);
glVertex2i(100,10);
glVertex2i(40,100);
glVertex2i(100,100);
glVertex2i(40,10);
glVertex2i(100,10);
glColor3f(1.0,0.0,0.0);
//Visible line
glVertex2i(50,60);
glVertex2i(70,40);
//Invisible line
glVertex2i(150,100);
glVertex2i(180,50);
glEnd();
glFlush();
}
void myInit(void)
{
glClearColor(0.0,0.0,0.0,1.0);
glPointSize(2.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0,200,0,200);
}
// Driver code
int main(int argc, char**argv)
{
cout<<" The coordinates of the clipping window are (40,100), (100,100), (100,10) and (40,40)"<<endl;
// First Line segment
// P11 = (5, 5), P12 = (7, 7) completely VISIBLE(inside)
cohenSutherlandClip(50, 60, 70, 40);
// P11 = (5, 5), P12 = (7, 7) completely INVISIBLE(outside)
cohenSutherlandClip(150, 100, 180, 150);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
// giving window size in X- and Y- direction
glutInitWindowSize(400,400);
glutInitWindowPosition(0,0);
// Giving name to window
glutCreateWindow("Cohen-Sutherland line clipping algorithm");
myInit();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
output:
