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Chalk Illusions

I have some crazy news! I was radiated by some radiation, and became radioactive. Over time, my radioactiveness decreased, and as it decreased, my mass decreased as well. I am now a foot shorter than I used to be, and weigh 50 pounds less! At the top of this post, you can see a picture which proves it. In the photo, I'm sitting on a weird box that materialized in the middle of the road...


Okay, so you probably know what's going on here. I didn't really shrink; I'm obviously sitting on a chalk drawing.

I designed the chalk drawing to look 3-dimensional when viewed from a certain angle. From other angles, it looks totally different; some of the lines that appear parallel in the photo aren't actually parallel at all. It only looks that way because it's an illusion.

Here's another example:


This was a little more complicated to draw. Not only were there parallel lines, but there were also circular shapes and hidden areas.

And here's my best chalk drawing so far. For this one, I used a pack of colorful Crayola chalk. Unlike other chalk I've used, the Crayola chalk didn't look like faded grey, and it even came with a stick of black chalk, which I used for the shadow on the sidewalk.

Anamorphic 3D chalk illusion

The main trick, when drawing a chalk image like this, is to set up a camera at the viewing point, and check it frequently while drawing. I've drawn pictures without a camera (by periodically placing myself at the viewing point instead of a camera), but it's not as easy, because humans have stereoscopic vision which ruins any false illusion of depth. A camera usually does not have stereoscopic vision, and does not present this problem.

When viewed from any position other than the intended location, the drawing doesn't look at all 3D.

Here's a series of photos showing how I drew the image:

Partial chalk illusionChalk illusion
Click to view larger

Despite the fact the the round areas look like squashed ellipses in the image, they are actually perfectly circular. The reason for this has to do with perspective and viewpoints. Basically, the surface of the sidewalk has the same slope as the horizontal surfaces of the chess piece, so the viewer can't tell the difference between a floating circle and a circle which is actually on the ground a distance away.

When done correctly, the final result can be rather convincing.

You can also combine the result with reality to get some really weird illusions. For the last photo in
this post, for example, I carefully placed 3 pieces of chalk so that they appeared as if they were on top of the chess piece.

So that's what I like to draw with chalk. Have any questions? Comment below!


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