public Vector4 ProcessFragment() { var pixel = new float[4]; _rtt.Activate(); GL.Viewport(0, 0, 1, 1); GL.ClearColor(0.1f, 0.3f, 0.6f, 0.9f); GL.Clear(ClearBufferMask.ColorBufferBit); //GL.Arb.ClampColor(ArbColorBufferFloat.ClampFragmentColorArb, ArbColorBufferFloat.RgbaFloatModeArb); //GL.Arb.ClampColor(ArbColorBufferFloat.ClampVertexColorArb, ArbColorBufferFloat.RgbaFloatModeArb); //GL.Arb.ClampColor(ArbColorBufferFloat.ClampReadColorArb, ArbColorBufferFloat.RgbaFloatModeArb); //GL.ClampColor(ClampColorTarget.ClampVertexColor, ClampColorMode.False); //GL.ClampColor(ClampColorTarget.ClampFragmentColor, ClampColorMode.False); //GL.ClampColor(ClampColorTarget.ClampReadColor, ClampColorMode.False); GL.Begin(BeginMode.Points); GL.Vertex3(0, 0, 0); GL.End(); GL.Flush(); GL.ReadPixels(0, 0, 1, 1, PixelFormat.Rgba, PixelType.Float, pixel); _rtt.Finish(); Utilities.CheckGL(); //_context.SwapBuffers(); return(new Vector4(pixel[0], pixel[1], pixel[2], pixel[3])); }