CircleDrawing.cpp

/*
 * GLUT Shapes Demo
 *
 * Written by Nigel Stewart November 2003
 *
 * This program is test harness for the sphere, cone
 * and torus shapes in GLUT.
 *
 * Spinning wireframe and smooth shaded shapes are
 * displayed until the ESC or q key is pressed.  The
 * number of geometry stacks and slices can be adjusted
 * using the + and - keys.
 */

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include <stdlib.h>
#include <stdio.h>

static int slices = 16;
static int stacks = 16;
int flag1 = 0,flag2=0, x00,y00,x11=-500,y11=400,radius=40,addx1=1,addy1=1,addx2=-1,addy2=-1,mass1=1,mass2=1;
/* GLUT callback Handlers */

static void resize(int width, int height){
    const float ar = (float) width / (float) height;
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-320, 319, -240, 239, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity() ;
}

void mouse(int button, int state, int mousex, int mousey)
{
    if(button==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
    {
        int mx = mousex;
        int my = mousey;
        //printf(" c1 %d %d\n",mx-320,-my+240);
        glutPostRedisplay();
        if(flag1==0){
            flag1=1;
            x00 = mx-320;
            y00 = -my+240;
        }
        else if(flag2==0){
            flag2=1;
            x11 = mx-320;
            y11 = -my+240;
        }
    }
}

void draw8way(int x,int y,int a, int b){
            glVertex2i(x+a, y+b);
            glVertex2i(y+a, x+b);
            glVertex2i(-y+a, x+b);
            glVertex2i(-x+a, y+b);
            glVertex2i(-x+a, -y+b);
            glVertex2i(-y+a, -x+b);
            glVertex2i(y+a, -x+b);
            glVertex2i(x+a, -y+b);
    }

void drawCircle1(int a,int b,int r){
    int x=0,y=r, d=5-4*r;
    draw8way(x,y,a,b);
    while(x<y){
        if(d<0){
            x++;
            d+= 8*x + 12;
        }
        else{
            x++,y--;
            d+= 8*x - 8*y + 20;
        }
        draw8way(x,y,a,b);
    }
}

bool collisionDetected(int x0,int y0,int x1,int y1){
    return ((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0) < 4*radius*radius);
}

static void display(void){

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glColor3d(1,1,1);
    glBegin(GL_LINES);
    glVertex2i(-320, 0);
    glVertex2i(319, 0);
    glVertex2i(0, -240);
    glVertex2i(0, 239);
    glEnd();
    glBegin(GL_POINTS);

    if(flag1==1){
        drawCircle1(x00,y00,radius);
        if(y00 + radius > 240)
            addy1 = -1;
        else if(y00 - radius < -240)
            addy1 = 1;
        else if(x00 + radius > 320)
            addx1 = -1;
        else if(x00 - radius < -320)
            addx1 = 1;

        x00+=addx1, y00+=addy1;
    }
    if(flag2==1){
        drawCircle1(x11,y11,radius);
        if(y11 + radius > 240)
            addy2 = -1;
        else if(y11 - radius < -240)
            addy2 = 1;
        else if(x11 + radius > 320)
            addx2 = -1;
        else if(x11 - radius < -320)
            addx2 = 1;
        else if(collisionDetected(x00,y00,x11,y11)){
            int tempx1 = addx1, tempy1 = addy1;
            addx1 = (2 * mass2 * addx2) / (mass1 + mass2);
            addy1 = (2 * mass2 * addy2) / (mass1 + mass2);
            addx2 = (2 * mass1 * tempx1) / (mass1 + mass2);
            addy2 = (2 * mass1 * tempy1) / (mass1 + mass2);

        }
        x11+=addx2, y11+= addy2;
    }
    glEnd();
    glutSwapBuffers();
}


static void key(unsigned char key, int x, int y)
{
    switch (key)
    {
        case 27 :
        case 'q':
            exit(0);
            break;

        case '+':
            slices++;
            stacks++;
            break;

        case '-':
            if (slices>3 && stacks>3)
            {
                slices--;
                stacks--;
            }
            break;
    }

    glutPostRedisplay();
}

static void idle(void)
{
    glutPostRedisplay();
}

/* Program entry point */

int main(int argc, char *argv[]){
    glutInit(&argc, argv);
    glutInitWindowSize(640,480);
    glutInitWindowPosition(10,10);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("Experiment 01");

    glutReshapeFunc(resize);
    glutDisplayFunc(display);
    glutKeyboardFunc(key);
    glutIdleFunc(idle);
    glutMouseFunc(mouse);

    glutMainLoop();



    return EXIT_SUCCESS;
}