How to plot grid refinement mesh


I have been follow course about the palabos grid refinement techniques:

However, when I was running showCases/gridRefinement2d example, I do not see how can I find which level has been applied where in the vtk file, does anybody can help or show one example of how can I check visually the grid refinement level?

Thank you

in 2D things are not so advanced. We directly developed things in 3D and 3D is not really reliable at the moment.
Sorry for this.
Best regards,