>>12933464you could find the (line)curves in 3d of the shapes, but a more efficient way would to just find the surface of the butt and then choose whichever section you want of it. But you need to parametrize the problem.
What you are asking is super general, you need to be more specific? In what sense do you want to use this kind of information? Do you want to redraw the picture in 2D? Do you want to create a 3D print of a 2D picture? Do you want to use algebraic functions or analytic geometry to parametrize your data?
Fun thing to read on wikipedia: Radon transform - you may imagine ultrasound only reads a 2D data, or to be specific a 2D surface of data (belly and the parallel surface of belly inside of a pregnant mother for example). But what you see sometimes is a projection of a 3D baby. How do they do that? With a clever transformations of the coordinates and good understanding of the system.
