* Features [12/20]

 - [X] Perspective projection
 - [X] Ray-sphere intersection
 - [-] Ray-plane and derived intersections
   - [X] Ray-plane
   - [X] Ray-disk
   - [ ] Ray-triangle
   - [ ] Ray-box
 - [ ] Ray-mesh intersection
 - [ ] Octree mesh
 - [X] Directional lights
 - [X] Point lights
 - [X] Spotlights
 - [ ] Area lights
   - [ ] Sphere lights
   - [ ] Box/planar lights
 - [X] Phong shading
 - [X] Specular reflections
 - [X] Transmission
 - [ ] Scene description input files (JSON)
 - [X] Indirect illumination
 - [ ] Glossy reflections
 - [X] Image based lighting
 - [X] HDR light probes for IBL
 - [X] Tone mapping
 - [ ] Texture mapping
 - [ ] Photon mapping

* Junk

#+BEGIN_SRC c++
  void scene_1(vector<Figure *> & vf, vector<Light *> & vl, Environment * & e, Camera * c) {
    Sphere * s;
    Plane * p;
    Disk * d;
    DirectionalLight * l;

    e = new Environment(NULL, false, vec3(0.7f, 0.4f, 0.05f));
    
    s = new Sphere(1.0f, 1.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 0.0f, 0.0f);
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(-1.0f, 1.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(0.0f, 1.0f, 0.0f);
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(1.0f, -1.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(0.0f, 0.0f, 1.0f);
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(-1.0f, -1.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 0.0f, 1.0f);
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(0.0f, 0.0f, -2.0f, 1.0f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    vf.push_back(static_cast<Figure *>(s));

    p = new Plane(vec3(0.0f, -1.5f, 0.0f), vec3(0.0f, 1.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(1.0f, 0.5f, 0.4f);
    vf.push_back(static_cast<Figure *>(p));

    s = new Sphere(-1.5f, 0.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 1.0f);
    s->m_mat->m_rho = 0.3f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(1.5f, 0.0f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 1.0f);
    s->m_mat->m_rho = 0.08f;
    s->m_mat->m_refract = true;
    s->m_mat->m_ref_index = 1.1f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(0.0f, 1.5f, -2.0f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 1.0f);
    s->m_mat->m_rho = 0.5f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(0.0f, 0.0f, -1.0f, 0.25f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 1.0f);
    s->m_mat->m_rho = 0.1f;
    vf.push_back(static_cast<Figure *>(s));

    d = new Disk(vec3(-0.0f, -0.0f, -0.5f), vec3(0.0f, 0.0f, 0.1f), 0.25f);
    d->m_mat->m_diffuse = vec3(1.0f, 0.0f, 0.0f);
    d->m_mat->m_rho = 0.3f;
    d->m_mat->m_refract = true;
    d->m_mat->m_ref_index = 1.33f;
    vf.push_back(static_cast<Figure *>(d));

    l = new DirectionalLight();
    l->m_position = normalize(vec3(1.0f, 1.0f, 1.0f));
    l->m_diffuse = vec3(0.0f, 1.0f, 1.0f);
    vl.push_back(static_cast<Light *>(l));

    l = new DirectionalLight();
    l->m_position = normalize(vec3(-1.0f, 1.0f, 1.0f));
    l->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    vl.push_back(static_cast<Light *>(l));

    l = new DirectionalLight();
    l->m_position = normalize(vec3(0.0f, 1.0f, -1.0f));
    l->m_diffuse = vec3(1.0f, 0.0f, 1.0f);
    vl.push_back(static_cast<Light *>(l));
  }

  void scene_2(vector<Figure *> & vf, vector<Light *> & vl, Environment * & e, Camera * c) {
    Sphere * s;
    Plane * p;
    Disk * d;
    PointLight * l;
    
    s = new Sphere(0.2f, 0.0f, -0.75f, 0.25f);
    s->m_mat->m_diffuse = vec3(1.0f);
    s->m_mat->m_rho = 0.2f;
    vf.push_back(static_cast<Figure *>(s));

    p = new Plane(vec3(0.0f, -1.0f, 0.0f), vec3(0.0f, 1.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(0.0f, 1.0f, 0.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    p = new Plane(vec3(-2.0f, 0.0f, 0.0f), vec3(1.0f, 0.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(1.0f, 0.0f, 0.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    p = new Plane(vec3(2.0f, 0.0f, 0.0f), vec3(-1.0f, 0.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(0.0f, 0.0f, 1.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    p = new Plane(vec3(0.0f, 1.0f, 0.0f), vec3(0.0f, -1.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(0.0f, 1.0f, 1.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    p = new Plane(vec3(0.0f, 0.0f, -2.0f), vec3(0.0f, 0.0f, 1.0f));
    p->m_mat->m_diffuse = vec3(1.0f, 0.0f, 1.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    p = new Plane(vec3(0.0f, 0.0f, 1.1f), vec3(0.0f, 0.0f, -1.0f));
    p->m_mat->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));

    s = new Sphere(-0.5f, -0.5f, -1.5f, 0.5f);
    s->m_mat->m_diffuse = vec3(0.0f);
    s->m_mat->m_rho = 1.0f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(-0.5f, -0.5f, 0.6f, 0.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    s->m_mat->m_refract = true;
    s->m_mat->m_ref_index = 1.33f;
    vf.push_back(static_cast<Figure *>(s));

    d = new Disk(vec3(-0.25f, 1.0f, -1.0f), vec3(1.0f, 0.0f, 0.0f), 0.25f);
    d->m_mat->m_diffuse = vec3(1.0f);
    vf.push_back(static_cast<Figure *>(d));

    d = new Disk(vec3(0.25f, 1.0f, -1.0f), vec3(-1.0f, 0.0f, 0.0f), 0.25f);
    d->m_mat->m_diffuse = vec3(1.0f);
    vf.push_back(static_cast<Figure *>(d));

    d = new Disk(vec3(0.0f, 1.0f, -1.25f), vec3(0.0f, 0.0f, 1.0f), 0.25f);
    d->m_mat->m_diffuse = vec3(1.0f);
    vf.push_back(static_cast<Figure *>(d));

    d = new Disk(vec3(0.0f, 1.0f, -0.75f), vec3(0.0f, 0.0f, -1.0f), 0.25f);
    d->m_mat->m_diffuse = vec3(1.0f);
    vf.push_back(static_cast<Figure *>(d));

    l = new PointLight();
    l->m_position = vec3(0.0f, 0.9f, -1.0f);
    l->m_diffuse = vec3(1.0f);
    vl.push_back(static_cast<Light *>(l));
  }

  void scene_3(vector<Figure *> & vf, vector<Light *> & vl, Environment * & e, Camera * c) {
    Sphere * s;
    Disk * d;
    // SpotLight * l;
    // DirectionalLight * l2;
    vec3 eye = vec3(0.0f, 1.5f, 1.0f);
    vec3 center = vec3(0.0f, 0.0f, -2.0f);
    vec3 left = vec3(-1.0f, 0.0f, 0.0f);

    e = new Environment("textures/pisa.hdr");
    
    c->m_eye = eye;
    c->m_look = center;
    c->m_up = cross(normalize(center - eye), left);
    c->translate(vec3(1.0f, 0.0f, 0.0f));
    //c->roll(15.0f);

    // s = new Sphere(0.0f, -0.15f, -2.0f, 1.0f);
    // s->m_mat->m_diffuse = vec3(1.0f, 0.5f, 0.0f);
    // s->m_mat->m_specular = vec3(0.3f);
    // s->m_mat->m_shininess = 5.0f;
    // s->m_mat->m_rho = 0.4f;
    // s->m_mat->m_refract = true;
    // s->m_mat->m_ref_index = 1.33f;
    // vf.push_back(static_cast<Figure *>(s));

    // s = new Sphere(0.0f, -0.15f, -2.0f, 0.5f);
    // s->m_mat->m_diffuse = vec3(0.0f);
    // s->m_mat->m_specular = vec3(0.0f);
    // s->m_mat->m_rho = 0.0f;
    // s->m_mat->m_refract = true;
    // s->m_mat->m_ref_index = 2.6f;
    // vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(2.0f, 0.0f, -2.0f, 1.5f, new HeidrichSeidelAnisotropicBRDF(vec3(0.0f, 1.0f, 0.0f)));
    s->m_mat->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    s->m_mat->m_shininess = 128.0f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(-1.0f, 0.0f, -3.25f, 1.5f);
    s->m_mat->m_diffuse = vec3(1.0f, 0.0f, 1.0f);
    s->m_mat->m_rho = 0.4f;
    vf.push_back(static_cast<Figure *>(s));

    s = new Sphere(1.0f, 0.0f, -3.25f, 1.5f);
    s->m_mat->m_diffuse = vec3(1.0f);
    s->m_mat->m_rho = 0.4f;
    vf.push_back(static_cast<Figure *>(s));
    
    d = new Disk(vec3(1.0f, -1.5f, -3.25f), vec3(0.0f, 1.0f, 0.0f), 3.0f);
    d->m_mat->m_diffuse = vec3(0.0f, 0.5f, 0.5f);
    d->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(d));
    
    // l = new SpotLight();
    // l->m_position = normalize(vec3(-2.0f, 1.5f, -1.0f));
    // l->m_diffuse = vec3(1.0f, 1.0f, 0.0f);
    // l->m_spot_dir = normalize(vec3(0.5f, 0.0f, -2.5f) - vec3(-2.0f, 1.5f, -1.0f));
    // l->m_spot_cutoff = 89.0f;
    // l->m_spot_exponent = 10.0f;
    // vl.push_back(static_cast<Light *>(l));

    // l2 = new DirectionalLight();
    // l2->m_position = normalize(vec3(-1.0f, 0.7f, 1.0f));
    // l2->m_diffuse = vec3(1.0f, 1.0f, 1.0f);
    // vl.push_back(static_cast<Light *>(l2));

    // l2 = new DirectionalLight();
    // l2->m_position = normalize(vec3(-0.5f, 0.7f, 1.0f));
    // l2->m_diffuse = vec3(0.0f, 0.0f, 1.0f);
    // l2->m_specular = vec3(0.0f, 0.0f, 1.0f);
    // vl.push_back(static_cast<Light *>(l2));

    // l = new DirectionalLight();
    // l->m_position = normalize(vec3(1.0f, 0.0f, 1.0f));
    // l->m_diffuse = vec3(0.5f);
    // vl.push_back(static_cast<Light *>(l));
  }

  void scene_4(vector<Figure *> & vf, vector<Light *> & vl, Environment * & e, Camera * c) {
    Sphere * s;
    Plane * p;

    e = new Environment("textures/pisa.hdr");
    
    s = new Sphere(0.0f, 0.0f, -2.0f, 1.0f);
    s->m_mat->m_diffuse = vec3(1.0f);
    s->m_mat->m_rho = 0.3f;
    vf.push_back(static_cast<Figure *>(s));

    p = new Plane(vec3(0.0f, -1.0f, 0.0f), vec3(0.0f, 1.0f, 0.0f));
    p->m_mat->m_diffuse = vec3(1.0f);
    p->m_mat->m_specular = vec3(0.0f);
    vf.push_back(static_cast<Figure *>(p));
  }

#+END_SRC