TFrameBufferObject = class
  protected
    FBO:   GLuInt;
    depth: GLuInt;
    tex:   GLuInt;

    FWidth,
    FHeight: Integer;
  public
    procedure Bind;
    procedure UnBind;

    constructor Create(aWidth, aHeight: Integer);
    destructor Destroy; override;

    property Texture: GLuInt read tex;
  end;

implementation

var
  CurrentFrameBuffer: TFrameBufferObject = nil;

procedure TFrameBufferObject.Bind;
begin
  if CurrentFrameBuffer <> nil then CurrentFrameBuffer.UnBind;

  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
  glPushAttrib(GL_VIEWPORT_BIT);
  glViewPort(0, 0, FWidth, FHeight);

  CurrentFrameBuffer:= self;
end;

procedure TFrameBufferObject.UnBind;
begin
  if CurrentFrameBuffer <> self then begin
    showMessage('tried to unbind inactive FrameBuffer');
    exit;
  end;

  glPopAttrib;
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

  CurrentFrameBuffer:= nil;
end;

constructor TFrameBufferObject.Create;
var
  error: GlEnum;
begin
  inherited Create;
  glGenFramebuffersEXT(1, @FBO);
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBO);

  glGenRenderbuffersEXT(1, @depth);
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depth);
  glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, aWidth, aHeight);
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
    GL_RENDERBUFFER_EXT, depth);

  glGenTextures(1, @tex);
  glBindTexture(GL_TEXTURE_2D, tex);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  aWidth, aHeight, 0, GL_RGBA, GL_Float, nil);
  glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0);

  error := glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
  case error of
    GL_FRAMEBUFFER_COMPLETE_EXT:
      Exit;
    GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
      raise Exception.Create('Incomplete attachment');
    GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
      raise Exception.Create('Missing attachment');
    GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
      raise Exception.Create('Incomplete dimensions');
    GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
      raise Exception.Create('Incomplete formats');
    GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
      raise Exception.Create('Incomplete draw buffer');
    GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
      raise Exception.Create('Incomplete read buffer');
    GL_FRAMEBUFFER_UNSUPPORTED_EXT:
      raise Exception.Create('Framebufferobjects unsupported');
  end;

  FWidth:= aWidth;
  FHeight:= aHeight;

  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);                                               {edit}
end;

destructor TFrameBufferObject.Destroy;
begin
  glDeleteFramebuffersEXT(1, @FBO);
  glDeleteRenderbuffersEXT(1, @depth);
  glDeleteTextures(1, @tex);
end;

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  aWidth, aHeight, 0, GL_RGBA, GL_Float, nil);