anchor.diff:  open System
   open NUnit.Framework
   open FsUnit
  +open OpenTK.Graphics.OpenGL4
   open Aardvark.Rendering.GL
   open Aardvark.Base
   open Aardvark.Base.Incremental
  
positive.code:         
  
              clear.Run(RenderToken.Empty, fbo)
              OpenTK.Graphics.OpenGL4.GL.Sync()
              let token = RenderToken()
              task.Run(token, fbo)
              OpenTK.Graphics.OpenGL4.GL.Sync()
              Log.line "%d objects" token.DrawCallCount
              let pi = runtime.Download(color, PixFormat.ByteRGBA)
              pi.SaveAsImage(@"C:\Aardwork\urdar.png")
              OpenTK.Graphics.OpenGL4.GL.Sync()
              Log.line "starting update test"
              let mutable iterations = 0
              let sw = Stopwatch()
  
negative.code: 
  
          clear.Run(RenderToken.Empty, fbo) |> ignore
          GL.Sync()
          let token = RenderToken()
          task.Run(token, fbo)
          GL.Sync()
          Log.line "%d objects" token.DrawCallCount
          let pi = runtime.Download(color, PixFormat.ByteRGBA)
          pi.SaveAsImage(@"C:\Aardwork\gugu.png")
          GL.Sync()
          //task2.Run fbo |> ignore
          //OpenTK.Graphics.OpenGL4.GL.Sync()
  
  