Midpoint Circle Drawing Algorithm Implementation using OpenGL

OpenGL_CircleAlog.cpp

#include <stdio.h>
#include <iostream>
#include <GL/glut.h>
using namespace std;

int pntX1, pntY1, r;

void plot(int x, int y)
{
	glBegin(GL_POINTS);
	glVertex2i(x+pntX1, y+pntY1);
	glEnd();
}


void myInit (void)
{
	glClearColor(1.0, 1.0, 1.0, 0.0);
	glColor3f(0.0f, 0.0f, 0.0f);
	glPointSize(4.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0, 640.0, 0.0, 480.0);
}


void midPointCircleAlgo()
{
	int x = 0;
	int y = r;
	float decision = 5/4 - r;
	plot(x, y);

	while (y > x)
	{
		if (decision < 0)
		{
			x++; 
			decision += 2*x+1;
		}
		else
		{
			y--;
			x++;
			decision += 2*(x-y)+1;
		}
		plot(x, y);
		plot(x, -y);
		plot(-x, y);
		plot(-x, -y);
		plot(y, x);
		plot(-y, x);
		plot(y, -x);
		plot(-y, -x);
	}

}

void myDisplay(void)
{
	glClear (GL_COLOR_BUFFER_BIT);
	glColor3f (0.0, 0.0, 0.0);
	glPointSize(1.0);

	midPointCircleAlgo();

	glFlush ();
}

void main(int argc, char** argv)
{	
	cout << "Enter the coordinates of the center:\n\n" << endl;

	cout << "X-coordinate   : "; cin >> pntX1;
	cout << "\nY-coordinate : "; cin >> pntY1;
	cout << "\nEnter radius : "; cin >> r;


	glutInit(&argc, argv);
	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize (640, 480);
	glutInitWindowPosition (100, 150);
	glutCreateWindow ("Line Drawing Alogrithms");
	glutDisplayFunc(myDisplay);
	myInit ();
	glutMainLoop();

}

THANK YOU

THANK YOU so much, really helping for my assignment

void draw_circle(Point p1,GLint radius)
{
    GLint x = 0;
    GLint y = radius;
    GLint p = 1- radius;

    void callcircle(Point , GLint ,GLint );

    callcircle(p1,x,y);

    while(x < y)
    {
        x++;
         if(p < 0)
        {
            p += 2*x +1;
        }
        else{
            y--;
            p += 2*(x-y)+1;
        }
        callcircle(p1,x,y);
    }
    
}
void callcircle(Point p, GLint x, GLint y)
{
		glVertex2f(p.x + x, p.y + y);
		glVertex2f(p.x - x, p.y + y);
		glVertex2f(p.x + x, p.y - y);
		glVertex2f(p.x - x, p.y - y);
		glVertex2f(p.x + x, p.y + y);
		glVertex2f(p.x - x, p.y + y);
		glVertex2f(p.x + x, p.y - y);
		glVertex2f(p.x - x, p.y - y);
		
}

It's not showing full circle when i used mid-point, Can I know what's the problem ?

THANKS FOR HELPING IN MY ASSIGNMENT :)

thank you,
just a suggestion in line 83:
glutCreateWindow ("Midpoint Algorithm");

@CleverFool77 you're overwriting the same pixel. Try this

                glVertex2f(p.x + x, p.y + y);
		glVertex2f(p.x - x, p.y + y);
		glVertex2f(p.x + x, p.y - y);
		glVertex2f(p.x - x, p.y - y);
		glVertex2f(p.y + x, p.x + y);
		glVertex2f(p.y - x, p.x + y);
		glVertex2f(p.y + x, p.x - y);
		glVertex2f(p.y - x, p.x - y);