Jeez, Stephen, if it were just CGI, there would be nothing particularly interesting about the video. If you check out YouTube and other websites for the "waterfall illusion", you'll find a number of "fake" video examples where the water is flowing backward because the video has been set to reverse. The interesting problem is when one sees it flowing backwards when other cues indicate that everything in real-time is going forward.
If Mcwolles video is just CGI, then it is uninteresting. If it is like a real 3-D Penrose staircase (like the one I linked to in an earlier post), then it becomes interesting because it is a true illusion. With CGI, one will see the water always flowing while in real life there is only one position that the illusion will work. Move from the position and the illusion is lost. Kinda like this: http://mindhacks.com/2006/02/22/3d-rooms/ The relevant concept is called anamorphosis and there's even a Wikipedia entry on it (yadda-yadda); see: http://en.wikipedia.org/wiki/Anamorphosis Look under the heading "impossible objects" for Escher relevance. As for putting in time and effort into understanding something, if one isn't willing to do so, which is it more telling about: the person or the phenomenon? -Mike Palij New York University [email protected] ********************* Original Message ********************* On Sun, 20 Feb 2011 10:29:09 -0800, Stephen Black wrote: I had complained that a site which Mike Palij had recommended for this demo turned out to be a disappointment. This was because the author claimed to have a good idea how it was done, but would not reveal it. Mike replied with a lecture on the topic of the privileged nature of the tricks of magicians and (I presume), that we were rude (or perhaps boorish) to ask to have it explained. I disagree. Psychologists have an interest in optical illusions in part because they help us to understand how the brain works That was the point of this thread and what we help students to do in the classroom, and we have nothing to apologize for in pursuing it. Inquiring minds want to know. Mike also wrote: > So, how many hours/days/weeks are you willing to spend to > figure out the solution? Not so many are now needed, perhaps. I sent it along to my techno- geek daughter, and she speculated that it was due to a motorized wheel and cgi water. I had seen this term "cgi" in some of the posted comments but didn't know what it meant. Now I do. "Cgi" stands for "computer-generated imagery". What she is suggesting is that this illusion, like the film "Avatar", was created on the screen rather than in our brains. Mcwolles may have taken a 3-dimensional representation of the Escher drawing along the lines suggested by Barbara's drawing, and superimposed on it an animation of water. It seems a plausible, parsimonious solution. So, no Ames messy basement room required, no real water flow at all. But if that's the way he did it, it's a disappointment, a trick rather than a true optical illusion. Still clever, I grudgingly admit. --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=8872 or send a blank email to leave-8872-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
