Drawing Circle with OpenGL

Question

I\'m trying to draw simple circle with C++/OpenGl

my code is:

#include 
#include 

void Draw() {
    glClear(GL_COLOR_         


        

Answer 1

#include 
#include 
#include 
#include 
#include 
#include 
#define window_width  1080  
#define window_height 720 
void drawFilledSun(){
    //static float angle;
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0, 0, -10);
    int i, x, y;
    double radius = 0.30;
    //glColor3ub(253, 184, 19);     
    glColor3ub(255, 0, 0);
    double twicePi = 2.0 * 3.142;
    x = 0, y = 0;
    glBegin(GL_TRIANGLE_FAN); //BEGIN CIRCLE
    glVertex2f(x, y); // center of circle
    for (i = 0; i <= 20; i++)   {
        glVertex2f (
            (x + (radius * cos(i * twicePi / 20))), (y + (radius * sin(i * twicePi / 20)))
            );
    }
    glEnd(); //END
}
void DrawCircle(float cx, float cy, float r, int num_segments) {
    glBegin(GL_LINE_LOOP);
    for (int ii = 0; ii < num_segments; ii++)   {
        float theta = 2.0f * 3.1415926f * float(ii) / float(num_segments);//get the current angle 
        float x = r * cosf(theta);//calculate the x component 
        float y = r * sinf(theta);//calculate the y component 
        glVertex2f(x + cx, y + cy);//output vertex 
    }
    glEnd();
}
void main_loop_function() {
    int c;
    drawFilledSun();
    DrawCircle(0, 0, 0.7, 100);
    glutSwapBuffers();
    c = getchar();
}
void GL_Setup(int width, int height) {
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glEnable(GL_DEPTH_TEST);
    gluPerspective(45, (float)width / height, .1, 100);
    glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitWindowSize(window_width, window_height);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
    glutCreateWindow("GLUT Example!!!");
    glutIdleFunc(main_loop_function);
    GL_Setup(window_width, window_height);
    glutMainLoop();
}

This is what I did. I hope this helps. Two types of circle are here. Filled and unfilled.