public void draw (Renderer renderer, Framebuffer framebuffer) {

        // Get camera values
        float aspect = framebuffer.getAspect();

        Camera camera = _cameras.get(_renderCamera);

        Mat4 projectionMatrix = camera.getProjectionMatrix(aspect);
        Mat4 viewMatrix       = camera.getViewMatrix();

        Vec3 cameraLocation = camera.getLocation().homogenize3();

        Light lights[] = getLights();

        // Draw all geometry objects
        for (Geometry geo : _geometries.values()) {

            if (!geo.isVisible()) {
                continue;
            }

            Mat4 modelMatrix = geo.getModelMatrix();
            Mat3 normalMatrix = geo.getNormalMatrix();

            // Draw all surfaces of each geometry
            Iterator<Surface> surfaces = geo.getSurfaces();
            while (surfaces.hasNext()) {

                Surface s = surfaces.next();

                SurfaceShader shader = s.getShader();

                /**
                 * TODO 5:
                 * - Pass normalMatrix to shader
                 * - Pass camera location and light sources to shader.
                 */

                /**
                 * TODO 3:
                 * - Calculate and set modelViewProjectionMatrix for shader.
                 */

                /**
                 * TODO 2:
                 * - Pass the geometry's modelMatrix to the shader.
                 */

                Mesh mesh = s.getMesh();

                renderer.draw(mesh, shader, framebuffer);