how to calculate the distance when working on anamorphosis art?

Question

I am working on a painting on a wall, and I notice there is something new if I look at the painting from another angle. I was wondering if there are some proper methods to identify or to work on this form of art? I have searched the internet but there must be some methods to calculate the distance or the size of the paintings...right?

Answer 1

Well, if you don't paint it while looking in a curved mirror, which is a bit awkward on a wall, then presumably you have to lay out a distorted grid, where rectangles or trapezoids represent squares on the original "proper" sketch.