I watched Inception last week. Fascinating movie. You should watch it too, if you haven’t yet.
Of course, this is not a movie review blog. But there is a connection with 3DTin. Stay with me.
The movie is about dreams. It’s about creating the dreams (the ones in the sleep) and then sharing them with others. There are special architects who build fantastic pieces of architecture in this subconscious world. Because they are in the dream, they can do things that can’t be done in real life. They can bend laws of physics and more. One such piece they build is Endless stairs, also known as Penrose stairs.
These stairs ascend or descend in a continuous loop. If a person is to use them, he will never leave them even if he ascends or descends for infinite time. Penrose stairs is an impossible object in real life. But as Arthur in the movie explains, it can be built in dreams.
Yesterday I tried to build these stairs (more correctly an illusion of them) in 3DTin. Check them out here. The illusion vanishes as soon as you click and rotate the view. In the movie too, they create an illusion. The stairs actually do end, they only appear to extend further (the fact that is used to get rid of one of Fischer’s bodyguards).
While building the stairs I realized one thing though. One can create such an illusion only in orthographic projection. Orthographic (a.k.a. parallel) projection is a way of drawing 3D objects that is mainly used by architects or designers. The key difference between Orthographic and Perspective projection is the change in size of objects depending on their distance from the viewer. In orthographic projection as an object moves away from the viewer its size doesn’t appear to change, however in perspective projection it appears to get smaller. The way we see our world in real life is perspective projection. I can’t imagine how things around us will look in Orthographic. So even if Arthur is to build an illusion of these stairs in dreams, the people he is fooling must be seeing it in orthographic.
When you load the Penrose stairs in 3DTin, they are shown in a particular orientation with orthographic projection. You can change the projection to Perspective, by clicking on the last icon in the toolbar on left hand side. Try to arrange the visual so that you can again create the same illusion. You will notice that it can’t be done. The illusion cannot hold if stairs that are farther appear smaller. That’s why it’s only possible in Orthographic.
Can we count this as a loop hole? Or do we dream in Orthographic?
P.S. In any case, it’s only a geek’s nit-pick. I thoroughly enjoyed the movie.