Left Pointing Arrow Illusion

Left Pointing Arrow Illusion

This is a model of an object that gives the illusion of an arrow that is always pointing to the left. Turn it 180 degrees so that you're looking at it from the opposite side and it's still pointing to the left! If you set it in front of a mirror, the image in the mirror will be pointing in the opposite direction!

There is also a right pointing version and there are versions of both with and without the support tear-away tabs. Also included is a stand on which the arrow can be set and then spun around.

The arrows need to be printed with supports and the support tear-away tabs make support removal very easy. They're designed to be used with the supports interface feature of Cura or similar feature in other slicers. If you're not familiar with the support interface it's essentially a raft for the model that is built at the top of the supports, but instead of being flat like the raft it is contoured and shaped the same as the bottom surface of the model. It's an excellent feature, but if you set the support Z distance fairly small to get a smoother surface, it's almost impossible to remove the supports. These tabs extend the support interface out from the model and provide an area to grab onto to tear away the supports from the model. The tab structures also have a full height tower to increase the time between layers so that the tiny top layers don't print too rapidly and end up being smeared around because of insufficient cooling time.

The stand has a spherical capped Reuleaux triangle base. The diameter of the post is 4.7 mm and the hole in the arrow has a diameter of 5.0 mm, so it has a 0.3 mm tolerance for fitting. Scale the stand up or down as you please if you think your printer can handle a tighter tolerance or if you think it needs to be looser.

Video Demonstration

The right pointing version is featured on a Chris Ramsay YouTube video.

Credit For Design

Thanks to Dr. Kokichi Sugihara, a professor at Meiji University in Tokyo, who created the right pointing arrow illusion as part of his research into the new field of “computational illusion”. You can read some more about his creations here and here. And thanks to Andraxis for creating the model from which this is remixed.

Some of My Designs

Click an image below (opens in a new tab) or go to my designs page and see them all.

If you see some thing that you like , please click the ^Like button and turn that heart red .