It took a fair amount of experimentation to create the 3-D surface. In fact, I would say this is still at the experimental level.
It required a degree of patience too, as each layer had to dry thoroughly before the next was added.
Finally, the use of values had to be adapted to the changing light conditions. So some pre-planning was, of necessity, thrown out the window. …Other than that, it was a proverbial piece of cake. – Pagani