Artists used to mark off walls into squares to transfer drawings to walls. It still required a lot of manual eyeballing and skill. Things got a lot easier when people realized they could use digital projectors to simply project the image to the wall and trace it. It still had problems in very bright locations or in narrow areas (like hallways) where you can’t get a single projection. You have to move the projector around and do lots of calibrating of scale to avoid introducing distortions.

Now, people are using VR headsets in AR mode so they can apply images to walls without the projectors. @katdieuxart demonstrates the technique.