What is the most effective optical illusion you know? (I've got a wall that I'd like to paint.)

I thought about doing this one

@DJMcSpookem oh that was the one I was looking for, thank you!!!

But it is probably a little bit too difficult to draw/paint

Glad to help :)

I wonder who made that originally

Would be fun to have as a (literal) wallpaper

So I'm working on something right now for my job, and I thought you all in here would find it interesting.

So during Evaporative coating, if you shine a laser through the glass being deposited on, and you know the wavelength of the laser and what material is being deposited, you can determine the thickness of the coating. And depending on the thickness of the coating at any given moment, that can either work constructively or destructively, so the laser will either transmit more or reflect more.

This goes up and down over time as well: Each time you deposit a quarter of the wavelength of the laser, it will go from max transmission to max reflectance, or vice versa.

So I'm writing some code that will monitor a coating in progress, read all of the transmission data points, and attempt to fit it to a parabola so we can 1) Count extremas in the transmission curve, and 2) Extrapolate to when the transmission will be at a certain value and stop.

After that, I'll work on an analysis tool. You're typically going to be depositing multiple (up to several hundred) layers, and each one can have a different material or laser wavelength. So one potential problem is that you don't want to switch the lasers wavelength too often. So I'll be working on a tool that will analyze a given deposition and determine which wavelengths will allow for the most accurate monitoring with the fewest wavelengths

@flawr (sorry for the interruption, I found the source:) victoriaskye.com/illusionart.html

You're not interrupting

@DJMcSpookem How many different kinds of lasers are used?

Wavelengths? I think usually as few as possible. Maybe up to a dozen, but I think a lot of them can be done with 1

@flawr Nice spooky avatar BTW

thanks, but I was lazy, it's the one I've used every year:)

@flawr I really like the gifs based on that illusion showing how everything really IS straight lines.

(click to enlarge) I tried to remove elements step by step and see whether any of the embellishments actually contribute to the illusions. What do you think?

I think it's mostly the small black/white squares at the corners.

Just found another source of some famous illusions: ritsumei.ac.jp/~akitaoka/index-e.html