There are multiple methods to accurately approximate the surfaces in 3D, usually this requires flattening them onto 2D graphs.

Planes

A 3D surface can be partially visualized as multiple 2D graphs, where one of the variables is set to a different constant for each one. If the shape still isn't apparent a second "cross section" can then be taken by setting a different parameter to different constants to get a better grasp of the shape.

Example

Using this shape and noticing that it's an even function about , we can see that the shape forms a sphere.

Using these two graphs we can clearly see that it forms an hourglass shape with rings of circles.