How I can show the transformation of a NON-rigid Registration in rectilinear grid

Hi, I have a displacement matrix (D) resulted from a Non-rigid registration (free form transformation) such that each element of D (e.g. D(x,y)) shows the direction and the distance that pixel (x,y) should go. I use "interp2" to warp my image by the displacement matrix D.

I need to show the transformation field like the one in the bottom right figure of ( http://www.daimi.au.dk/~noe/images/viscousfluid/fluidregmathdefexample.png )

but since I've used free form transformation the squares/lines breaks and doesn't show my transformation correctly. Do you have any idea how I can show the transformation like it's been shown in the above mentioned image?

Thank you