circles.cpp

#include <GLUT/GLUT.h>
#include<OpenGL/OpenGL.h>
#include<iostream>
//#include<time>
#include<cstdlib>

#include <cmath>
#include <cstdio>

float x_1=1.0,x_2=1.0;
float y_1=1.0,y_2=1.0;
float x_3=1.0;
float px=x_3;
float a1=0.0,a2=0.0,step=0.0005;

void initRendering()
{
    glEnable(GL_DEPTH_TEST);
}

void reshape(int w,int h)
{
    glViewport(0,0,w,h);
    
    glMatrixMode(GL_PROJECTION);
    
    glLoadIdentity();
    
    gluPerspective(45,w/h,1,200);
    
}

void keyPressed(int key,int x,int y)
{
    if(key==GLUT_KEY_LEFT)
    {}
}

void drawMainBall()
{
    glColor3f(0.3,0.3,0.3);
    
    glPushMatrix();
    
    glTranslatef(0.0,0.0,-5.0);
    
    glutSolidSphere(0.8,120,120);
    
    glPopMatrix();
    
}

void drawBalls()
{
    glColor3f(0.3,1.0,0.0);
    
    glPushMatrix();
    
    glTranslatef(x_1,y_1,-5.0);
    
    glutSolidSphere(0.2,20,20);
    
    glPopMatrix();
    
    glColor3f(1.0,0.0,0.0);
    
    glPushMatrix();
    
    glTranslatef(x_2,y_2,-5.0);
    
    glutSolidSphere(0.2,20,20);
    
    glPopMatrix();
    
}

void drawWireBall()
{
    glColor3f(0.3,0.0,1.0);
    
    glPushMatrix();
    
    glTranslatef(x_3,x_3,-5.0);
    
    glutWireSphere(0.2,20,20);
    
    glPopMatrix();
}


void update()
{
    a1+=step;
    a2-=step;
    
    x_1=cos(a1);
    y_1=sin(a1);
    x_2=cos(a2);
    y_2=sin(a2);
    x_3=cos(a2);
}
void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    
    glMatrixMode(GL_MODELVIEW);
    
    glLoadIdentity();
    
    //glShadeModel(GL_SMOOTH);
    if(px>x_3)
    {
        drawMainBall();
        drawWireBall();
    }
    else
    {
        drawWireBall();
        drawMainBall();
    }
    px=x_3;
    drawBalls();
    update();
    
    glutSwapBuffers();
}


int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
    
    glutInitWindowSize(800,800);
    
    glutCreateWindow("Collision Window");
    
    //initRendering();    //initialize 3d rendering
    
    glutDisplayFunc(display);
    
    glutIdleFunc(display);
    
    glutReshapeFunc(reshape);
    
    glutSpecialFunc(keyPressed);
    
    glutMainLoop();
    
    return(0);
}