// This code example is created for educational purpose
// by Thorsten Thormaehlen (contact: www.thormae.de).
// It is distributed without any warranty.

#include <GL/freeglut.h> // we use glut here as window manager
#define _USE_MATH_DEFINES
#include <math.h>

class Renderer {

public:
  float t;

public:
  Renderer() : t(0.0) {}

public:

  void resize(int w, int h) {
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective (30.0, (float)w/(float)h, 2.0, 20.0);
  }

  void display() {    
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    // camera orbits in the y=10 plane
    // and looks at origin
    double rad = M_PI / 180.0f * t;
    gluLookAt(10.0*cos(rad), 10.0 , 10.0*sin(rad), // eye
              0.0, 0.0, 0.0, // look at
              0.0, 1.0, 0.0); // up

    //draw cube at origin
    drawCube();

    glRotatef(45.0f, 0.0f, 0.0f, 1.0f);
    glTranslatef(2.5f, 0.0f, 0.0f );
    glScalef(0.5f, 0.5f, 0.5f);

    drawCube(); //draw transformed cube
  }

  void init() {
    glEnable(GL_DEPTH_TEST);
  }
private:
  void drawCube() {
    glColor3f(1.0,0.0,0.0);
    glBegin(GL_POLYGON);
    glVertex3f(-1.0f, 1.0f, 1.0f);
    glVertex3f(-1.0f,-1.0f, 1.0f);
    glVertex3f( 1.0f,-1.0f, 1.0f);
    glVertex3f( 1.0f, 1.0f, 1.0f);
    glEnd();
    glColor3f(0.0,1.0,0.0);
    glBegin(GL_POLYGON);
    glVertex3f( 1.0f, 1.0f,-1.0f);
    glVertex3f( 1.0f,-1.0f,-1.0f);
    glVertex3f(-1.0f,-1.0f,-1.0f);
    glVertex3f(-1.0f, 1.0f,-1.0f);
    glEnd();
    glColor3f(0.0,0.0,1.0);
    glBegin(GL_POLYGON);
    glVertex3f( 1.0f, 1.0f, 1.0f);
    glVertex3f( 1.0f,-1.0f, 1.0f);
    glVertex3f( 1.0f,-1.0f,-1.0f);
    glVertex3f( 1.0f, 1.0f,-1.0f);
    glEnd();
    glColor3f(1.0,1.0,0.0);
    glBegin(GL_POLYGON);
    glVertex3f(-1.0f, 1.0f,-1.0f);
    glVertex3f(-1.0f,-1.0f,-1.0f);
    glVertex3f(-1.0f,-1.0f, 1.0f);
    glVertex3f(-1.0f, 1.0f, 1.0f);
    glEnd();
    glColor3f(1.0,1.0,1.0);
    glBegin(GL_POLYGON);
    glVertex3f( 1.0f, 1.0f,-1.0f);
    glVertex3f(-1.0f, 1.0f,-1.0f);
    glVertex3f(-1.0f, 1.0f, 1.0f);
    glVertex3f( 1.0f, 1.0f, 1.0f);
    glEnd();
    glColor3f(0.0,1.0,1.0);
    glBegin(GL_POLYGON);
    glVertex3f( 1.0f, -1.0f, 1.0f);
    glVertex3f(-1.0f, -1.0f, 1.0f);
    glVertex3f(-1.0f, -1.0f,-1.0f);
    glVertex3f( 1.0f, -1.0f,-1.0f);  
    glEnd();
  }
};

//this is a static pointer to a Renderer used in the glut callback functions
static Renderer *renderer;

//glut static callbacks start
static void glutResize(int w, int h) 
{
  renderer->resize(w,h);
}

static void glutDisplay() 
{
  renderer->display();
  glutSwapBuffers();
}

static void timer(int v) 
{
  float offset = 1.0f;
  renderer->t += offset;
  glutDisplay();
  glutTimerFunc(unsigned(20), timer, ++v);
}

int main(int argc, char **argv) 
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
  glutInitWindowPosition(100,100);
  glutInitWindowSize(320, 320);

  glutCreateWindow("Demo for gluLookAt");

  glutDisplayFunc(glutDisplay);
  //glutIdleFunc(glutDisplay);
  glutReshapeFunc(glutResize);
  
  renderer = new Renderer;
  renderer->init();

  glutTimerFunc(unsigned(20), timer, 0);

  glutMainLoop();
}