code: function Fbo( gl )
  {
    this.gl = gl;
    this.width  = 0;
    this.height = 0;
  
    this.fbo = gl.createFramebuffer();
    this.bind();
  
    this.attachments     = {};
    this.attachmentsList = [];
  }
docs: @class
  @param {WebGLRenderingContext} gl      the webgl context this Fbo belongs to
  @param {Object} [opts]
  @param {boolean} [opts.depth=false] if true, a depth renderbuffer is attached
  @param {boolean} [opts.stencil=false] if true, a stencil renderbuffer is attached
  @param {GLenum|GLenum[]} [opts.type=GL_UNSIGNED_BYTE] the pixel type of the Fbo, can be gl.UNSIGNED_BYTE, gl.FLOAT, half.HALF_FLOAT_OES etc. you can also provide an array of types used as cascaded fallbacks
  @param {GLenum} [opts.format=GL_RGB]   the color attachment pixel format.
  @param {GLenum} [opts.internal=GL_RGB] the internal color attachment pixel format.