membuat lingkaran

 /* Praktikum 05
* Membuat objek lingkaran sederhana
*/

#include <iostream>
#include <windows.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <stdarg.h> 
#include <glut.h> 
#include<math.h>

using namespace std;

typedef unsigned char uchar;

// number of line segments
static int num_lines = 20;

// callback prototypes
void disp(void);
void keyb(uchar k, int x, int y);
void reshape(int x, int y);

// main
int main(int argc, char **argv){
 glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
  glutInitWindowSize(400,400);
  glutInitWindowPosition(100,100);
  glutCreateWindow("circle.cpp");
  glClearColor(0.0,0.0,0.0,0.0);
  glutDisplayFunc(disp);
  glutKeyboardFunc(keyb);
  glutReshapeFunc(reshape);
  glutMainLoop();
  return 0;
}

// disp
void disp(void){
  double angle;
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_LINE_LOOP);
    for(int i =0;i<num_lines;i++){
            angle = i*2*3.14/num_lines;
        glVertex2f(cos(angle),sin(angle));
    }
  glEnd();
  glutSwapBuffers();
}

// keyb
void keyb(uchar k, int x, int y){
  switch (k){
  case 'q':
    exit(0);
    break;
  case '+':
    if(num_lines < 99){
      num_lines++;
      cout << "Circle consists of " << num_lines << " lines " << endl;
      glutPostRedisplay();
    }
    break;
 case '-':
    if(num_lines >3){
      num_lines--;
      cout << "Circle consists of " << num_lines << " lines " << endl;
      glutPostRedisplay();
    }
    break;
  }
}

// reshape
void reshape(int x,int y){
  if(x<y)
    glViewport(0,(y-x)/2,x,x);
  else
    glViewport((x-y)/2,0,y,y);
}