Oblique mapping is a false orthographic projection! It's not an actual projection at all! ! More specifically, oblique measurement is a very convenient tool for beginners of solid geometry, but it doesn't exist at all! !

In the oblique mapping method, the essence is to use parallel projection, so the parallel projection of the original image can be obtained on three planes (xoy, yoz, xoz), and because the light travels in a straight line, the projections of the three planes are the same size as the original image, so there is no problem of being near big and far small.

However! In reality, there is no projection transformation to display other faces of the cube, while maintaining the projection scale of the cube without scaling or tilting it!

Actually, I am an engineer. If I want to find a parallel projection in a three-dimensional drawing, I must draw an isometric drawing, not an oblique drawing.