This was made many years ago for my Maths classroom. It is a good introduction for learning how to represent 3D shapes. It is also a very simple, but effective, optical illusion.

It was very easy to knit. Each cube is made as a module and the modules are then stitched together.

I made it in Aran yarn and used about 1150 metres of the variegated, and 750 metres each of the blue and the navy. It could be made in any thickness of yarn though, with thinner yarn, you might need to add more modules to get blanket size. The variegated yarn creates an interesting effect because the squares are knitted diagonally.