Stacked Square Optical Illusion - grade 6

This is a project I absolutely love - it always produces great results, it's fairly simple for students to follow, and it's a great lesson for shading and creating a 3D drawing!

I'm not sure what to call this illusion - I've seen it a few times, but there's never really been a name associated with it. to me it looks like stacked squares... soo.. stacked square illusion?

Here's how to do the stacked square illusion:

                       

I begin by giving my students a template that I've made with three lines, as you can see in the first picture. I like to give them a starting point, because students can get really caught up in drawing the lines straight or the perfect dimensions apart. Instead of having them use the side with the lines, I have them work from the backside of the paper, so they can faintly see the three lines through the paper, but they aren't actually a part of their final project. (I hope this makes sense.)

The first thing students do is connect the lines at the top and the bottom of the pate, and identify roughly where they thing the center of the shape is.

                      

The next thing they do is start drawing pairs of lines. If the pairs are above the center mark they drew, they point them upwards (if possible, I have them point the lines more gradually upwards as they go.) The other thing they must do is close the sides of their pairs of lines (since they're working from the backside of the paper, they won't actually have the three dark black lines that we began with, they'll just be seeing them from the other side of the sheet.)

                      

This is what they should have once they've worked up one side of the paper. Once they're at this point, they can flip their paper upside down, and do the same thing on the other side.

                           

This is the part that really makes the illusion stand out - under each set of two lines, they draw two nearly horizontal lines going towards the center of the shape. They must do it all for one side of the paper, then flip it upside down and do it for the other side.

                          

Once this is all done, they can begin to color! They need to choose a side that will be dark, and a side that will be light. To keep it simple, I have them pick a marker and a pencil crayon in the same color. The parts in between the colored sections is shaded in using a pencil - dark shading on the dark side, and lighter shading on the light side.

Once they've finished the illusion, I have them color in the background using Sharpie. They all turned out so, so well - I'd love to post them all!