I saw such a picture on Pinterest. In the picture you will see the overlap of the cube and the sphere. What is the "perspective relationship" of the sphere with the cube above and the hexagon below? Why does it look like it cuts off the right side of the hexagon incorrectly? Also, which books should I study to be able to make such paintings?
At the first glance it may look a constructed perspective drawing which contains many planar surfaces and edges plus spheres. One can easily think "Oh, the edges are not drawn parallel, so it's not a parallel projection, so it must have perspective - nice work!!!!"
But it's not a constructed perspective drawing, it's a piece of art built of elements which are common in technical drawing exercises. The ellipses belong to that category. The technical drawing elements are placed by eyeballing, no proper measurements nor orientation definition procedures are used. The intention was to produce a piece of art which only looks like it was a technical construction. The existence of your question proves that the artist has succeeded well in his work.
To stay in truth the drawing could in theory be a perspective drawing of a 3D scene, but the 3D objects would in that case be irreqular and their orientations would be complex - not many parallel planes nor edges.
Added later:
You asked in a comment how to construct right in a perspective drawing those ellipses which look like they are the sphere cut by those planes which make the hexagonal cylinder.
One exact way to get them right in a pencil drawing without cheating with a computer is to construct the drawing from perpendicular engineering drawings(* with sight lines (also called projectors). In 3D the ellipses are circles, so you can find as many points of them as you need. Making the projected image of those points you can fit to them ellipses.
Making a proper sight line construction of the attached monster in your question is a hefty task. At least I would have a great temptation to build the whole scene in a 3D program, print it on a big paper (total time = 1 hour or less) and then to draw a pencil copy of it on a light table - maybe another hour for copying all lines and curves and one more for copying the shading.
Here's the part you asked afterwards in a comment - the sphere, the hexagonal cylinder and the slicing plane ellipses (circles in 3D) - shown by a 3D program.
Drawing this in a computer took less than 2 minutes.
*) The perpendicular engineering drawings for the manual perspective drawing construction of the hex cylinder and the sphere are these:
The dashed lines present the cutting planes.
