OT: Musings on CFC afterimages

A *lot* better than many of the unworkable "illusions" presented at that other site.. That cut-and-fold "impossible" triangle was particularly bad, in that it had absolutely zero chance of "working" as-is. None of the optical "illusions" i tried worked. Call it a hoax site.

My intution was that the edges of the sides could not be parallel for the the illusion to work. However, intution failed me, since I tried it, and it works as advertised. I presume you understand that the result only looks like a solid impossible triangle from one point in space relative to it. From anywhere else it looks like what it is - an oddly cut and folded piece of paper.

The moving rings and moving stars worked for me - but the effect is reasonably subtle.

The "Love Test" illusion I've seen before, and I still find it quite surprising. You have to keep you eyes very still when looking at the words in the middle, and don't blink, otherwise the illusion is lost. If you have slightly twitchy eyes, you may not be able to see this illusion, because you won't be able to keep your eyes still for long enough.

It fits in with something I noticed years ago, which is that if you stare at a fixed point for a while, stationary things start to disappear from your peripheral vision. The "Love Test" illusion seems to be able to create that effect very quickly for some reason.

Sylvia.

Outstanding!

...Jim Thompson

• There was no way to "close" the thing without severe bending and possible tearing. I could have done an infinitely better construction from scratch, it was *that* bad.

Where's "WhySoSerious?" when you need him? (Probably still trying to come up with a plausible reason for not handling high ohm resistors by their leads...)

Where did you even find them?

Thanks, Rich

Here is another site with a range of common illusions.

Regards, Martin Brown

Or shaking his head at the number of people who don't seem to get his style of humour.

Sylvia.

Er, it doesn't close. It's not meant to close. Here's how it works.

My effort is pretty rough and ready. With more time and stiffer paper, I'm sure a good result can be obtained.

Sylvia.

A sane person would figure out that it wasn't working.

Only that it's not working with a number of people.

Sylvia.

Now *THAT* is more like it!! I tried over a dozen and they all worked except for the grey (both spellings are acceptable) stripes.

Since i am on dial-up, "youtube" is out. Visualize the cut but unfolded paper, and then (following the minimal and megar instructions) fold the paper so the printing "stands out" or the dotted lines get stretched and not compressed (an "outie" not an "innie"). I wind up with a loooong piece of paper (almost a box) on the left that goes nowhere. And that triangle-end thinggis (highly technical term) on the right also goes nowhere.

Where "a number" is the universal set.

Yup. That's pretty much how it is. Then you sit it on the floor and look at it from the right direction.

Sorry about the focus, but you'll get the idea.

But move away from that position a bit, and you get

Note that I haven't changed the paper model at all between these two pictures.

From another direction it's:

The air movement may have tilted it a bit.

Sylvia.

Thanks for the photos; they make it possible.

Having reflected on that, I think my intuition was right - in theory. Because one of the sides of the triangle is actually pointing in a different direction from what appears to be the case, perspective is distorting it, and it should be shaped to as to correct for that distortion.

However, in practice it seems the distortion is not enough to matter for the purpose of creating the illusion, and one can get away with ignoring it.

Sylvia.