Lab_14

//CS334 - Lab 14, Group 5


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

float segments= 360;

void drawEllipse()
{
    glClear(GL_COLOR_BUFFER_BIT);   //flush gl

    float cx= 50.0f, cy= 50.0f, rx= 40.0f, ry= 30.0f; //, segments= 20.0f;

    float theta= 2 * 3.1415926 / segments;
    float cos_t= cosf(theta);//precalculate the sine and cosine
    float sin_t= sinf(theta);
    float temp, x= 1, y= 0;


    glBegin(GL_LINE_LOOP);
    for(int ctr = 0; ctr < segments; ++ctr)
    {
        //apply radius and offset
        glColor3f(1.0, 0.0, 0.0);   //red
        glVertex2f(x * rx + cx, y * ry + cy);//output vertex

        //apply the rotation matrix
        temp = x;   //temp store
        x = cos_t * x - sin_t * y;
        y = sin_t * temp + cos_t * y;
    }
    glEnd();

    glFlush();
}


int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("CS334 - lab14");

    glClearColor(0, 0, 0, 0);   //background
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(0, 100, -10, 100);

    glutDisplayFunc(drawEllipse);
    glutMainLoop();

    return EXIT_SUCCESS;
}