Levitation Illusions

[crocodile deathroll]

I know the secrets of a few levitation illusions, but just had a little brain wave for another one. That is to create a false shadow which could be sprayed or even just a dark wet patch beneath the object at the object is dragged away it reveals a wet patch that is beneath it the same shape. People get the illusion that the object is rising as it casts a shadow beneath it. You just try slowly picking up a CD case up off your desk and you notice it do not change. The only indication you get that it is rising is change in the shadow beneath it.

 

[davidhorman]

In a simple world, like the world of a raytracer, that might work, but there are more clues to the height of an object than it's shadow. Whether you paint the fake shadow or not, the object will still have a real shadow that you'll have to keep hidden. The effect definitely won't work "live" because people have stereoscopic vision that lets them determine 3D positions even without other clues. And even in 2D, those other clues (like other lighting effects and focus) would usually be enough to give an indication of the position of the object.

There was an example of just this on one of Randi's commentaries once. Some loon in Russia claimed to have invented some kind of hovering pogo stick, and part of the proof was a photo, taken roughly from above, showing a (probably fake) shadow under the pogo stick. That effect was fairly convincing, but the photograph was black and white and pretty grainy, and the effect certainly wouldn't have worked live.

David

 

[crocodile deathroll]

However stereoscopic vision is not an issue for cameras. This is how the some of the more modern day illusions you observe back home on you televisions sets are executed.

If I really was out to give the illusion a bit more polish then a change in perspective is another important clue. I think I could overcome that by tilting (or hinging) the object back as you are dragging it away from the fake painted shadow would overcome that. And you may get a very good illusion of a levitation for up to a meter up off the ground. Any further then I may running into problems.