 class EAGLOutputFrameBuffer: OutputFrameBuffer {
     private var _fbo: GLuint = 0
     private var _rbo: GLuint = 0
-    private var _dbo: GLuint = 0
     private var _width: GLsizei = 0
     private var _height:GLsizei = 0
     private let _layer: CAEAGLLayer

        glGenFramebuffers(1, &_fbo)
        glBindFramebuffer(GLenum(GL_FRAMEBUFFER), _fbo)
        
        glGenRenderbuffers(1, &_rbo)
        glBindRenderbuffer(GLenum(GL_RENDERBUFFER), _rbo)
        EAGLContext.current().renderbufferStorage(Int(GL_RENDERBUFFER), from: _layer)

                                  GLenum(GL_COLOR_ATTACHMENT0),
                                  GLenum(GL_RENDERBUFFER),
                                  _rbo)
        
        glGetRenderbufferParameteriv(GLenum(GL_RENDERBUFFER),
                                     GLenum(GL_RENDERBUFFER_WIDTH),
