In Fig. 4 we compare a simulation of stroxels and their practical realization. Typically different strokes are drawn in our simulation and by the robot within the feedback loop; in general, however, the gray-scale values are simulated quite faithfully. Some differences can be seen though: strokes are darker than assumed, their width is larger and also their shapes do not really match our simulation. As mentioned above, our feedback loop allows the process to adapt to the so far created gray-scale values on the canvas. This limits the overall error.