06. Concentric circle using midpoint algo.cpp

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

int pntX1, pntY1, r1,r2,r3;
int pntX2, pntY2;
int pntX3, pntY3;
int flag =1;

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

void plot2(int x, int y)
{
        glBegin(GL_POINTS);
        glVertex2i(x+pntX1, y+pntY1);
        glEnd();
}

void plot3(int x, int y)
{
        glBegin(GL_POINTS);
        glVertex2i(x+pntX1, y+pntY1);
        glEnd();
}

void plot_off(int x, int y)
{
        glBegin(GL_POINTS);
        glClear (GL_COLOR_BUFFER_BIT);
        glColor3f (1.0, 1.0, 1.0);
        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 = r1;
        float p = 5/4 - r1;
        plot(x, y);

        while (y > x)
        {
                if (p < 0)
                {
                        x++; 
                        p += 2*x+1;
                }
                else
                {
                        y--;
                        x++;
                        p += 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 midPointCircleAlgo2()
{
        int x = 0;
        int y = r2;
        float p = 5/4 - r2;
        plot2(x, y);

        while (y > x)
        {
                if (p < 0)
                {
                        x++; 
                        p += 2*x+1;
                }
                else
                {
                        y--;
                        x++;
                        p += 2*(x-y)+1;
                }
                plot2(x, y);
                plot2(x, -y);
                plot2(-x, y);
                plot2(-x, -y);
                plot2(y, x);
                plot2(-y, x);
                plot2(y, -x);
                plot2(-y, -x);
        }

}
void midPointCircleAlgo3()
{
        int x = 0;
        int y = r3;
        float p = 5/4 - r3;
        plot3(x, y);

        while (y > x)
        {
                if (p < 0)
                {
                        x++; 
                        p += 2*x+1;
                }
                else
                {
                        y--;
                        x++;
                        p += 2*(x-y)+1;
                }
                plot3(x, y);
                plot3(x, -y);
                plot3(-x, y);
                plot3(-x, -y);
                plot3(y, x);
                plot3(-y, x);
                plot3(y, -x);
                plot3(-y, -x);
        }

}

void midPointCircleAlgo_off()
{
        int x = 0;
        int y = r1;
        float p = 5/4 - r1;
        plot_off(x, y);

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

}

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

        midPointCircleAlgo();
        midPointCircleAlgo2();
        midPointCircleAlgo3();
                glFlush ();
        while(1)
        {
               
                int temp = r2;
                r2 = r3;
                cout << "\nEnter new radius:\n\n" << endl;
                r3=r3+1;
                flag++; 

        
                midPointCircleAlgo_off();
                printf("\nOld circle removed");
                glColor3f (0.0, 0.0, 0.0);
                glPointSize(1.0);
                midPointCircleAlgo3();
                printf("\nNew circle drawn");
                Sleep(200);
                r1 = temp;
                //glFlush ();
                glutSwapBuffers();
				
        }
        glFlush();
}

void main(int argc, char** argv)
{        
        cout << "Enter the coordinates of the center:\n\n" << endl;
        
        
        cout << "Enter X-coordinate   : "; cin >> pntX1;
        cout << "Enter Y-coordinate : "; cin >> pntY1;
        cout << "\nEnter 1st radius : "; cin >> r1;
        cout << "\nEnter 2nd radius : "; cin >> r2;
        cout << "\nEnter 3rd radius : "; cin >> r3;
        


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

        myInit ();
        glutMainLoop();

}