Working with waves shows that an inverted wave (polar reversal) over another that is otherwise the same causes both to be "invisible" even though they are technically both still there. In fact, it is the existence of both together, one inverted, that makes the seeming invisibility in the first place. As soon as even the slightest facet of one of these "twins" is changed, an individual point of one becomes known (being the only point known for the most part, depending on how "wide" or "deep" the change in one is, although other aspects may be colored by the additional energy of opening a wider deeper "gate" so to speak. This is only at one level though, even so much to say as only two-dimensional, so imagine the higher potential for such things, including three-dimensional reality and the four-dimensional path if including it as time rather than geometrical four-dimensions.
Here is a story. You have two masks of the type where it may be difficult to tell if you are looking into the mask (from behind) or if the mask is facing you, and even a photographic negative, depending on light source, would imply different three-dimensional aspects, visually. Now, there are different scenarios for these two masks depending on their polarity - this example concerned with "approach" only. One can be facing the other and approaching it. They are then face to face, perhaps even "kissing". One can be approaching the other, but facing the opposite direction, so neither can ever "see" the other, representing Janus in a way (thus, even "seeing two different worlds" equally viable for either). One can be facing the same direction as the other and actually "blend" into it, making two layers of "one" mask, and becoming stronger with the two combined layers into one whole "layer". If one is the polar opposite and one is facing the same direction as the other, they, together, become completely invisible. This mask "analogy" has been with me for some time, and there are other possibilities of course, including either of them being at any of the 360 degree angles relative to each other.
Being that points of polarity reversal can be isolated, it is also possible to end up with only the eyes of the one implied mask, only the mouth, the nose, the ears, or basically any surface area that is not the direct polar opposite of the other. In terms of the higher dimensions, say fifth-dimensional, that would be difficult to even begin to imagine in potential. It is easy to render polarity "tricks" in the digital world. It is very precise and "clean" and is what I use to determine the exact nature of an effects VST on a sound wave or instrument track for example. Doing so, I can immediately tell if the VST is feasible or if the programmer or company is lying about it (and oh what fun I have in this). A lot of these have random nuances, so viable full reversal does not "close the gate" so to speak and the VST is not even stable - almost like a lightning effect behind a white picket fence. Similar tricks can be done with imagery and even English writing (based on set letter frequency - although the table may vary somewhat source to source, but they all start with "E" and "T" of course), although there is more to consider - for example, should you use the mistake in the writing, or correct it prior to the work?
There are, of course, other potentials relative to the masks. One can be looking down and the other "ahead". One can be looking down and the other up, or both looking down and so on or becoming invisible in any same-facing orientation if one is the polar opposite; in this case, using the spherical potential rather than just the vertical 360 degrees.
With dreams, most people make the mistake of putting them in the "same basket" so to speak. The problem is that dreams may occur in many different levels of mind and spirit and at many different "bands", some even blending with the fractal continuity of the universe itself - so much so that they often have many different layers, each with its own meaning (and as I have learned, dreams that are mostly precognitive, as in my case, usually have other meaningful associations - especially due to their composite nature). Dreams may be the result of everything from subtle cellular energy and "memory", a recombining of recent events, a lucid excursion, based mostly on environmental sounds (especially if sleeping in front of the television when it is on - which is about the worst thing a person can do to themselves - sleeping-in-front-of-television dreams are "forced" - much like my programmed dreams using photo projection and special audio - and likely not to mean much relative to other possible layers), and of course phasing into the higher dimensions and non-linear "time" - or infinity/universality/eternity.
The so-called spinning dancer / spinning girl, etc. ceases to become an "optical illusion" once you are able to fully control it to a point where she does not even spin at all, but merely kicks to the left and to the right (and only spins in either direction, any number of times you want, when you "will" her to). This level of mental control is not even difficult for me contrary to all the nonsense on the Internet. At any right, because of such optical illusions (for "every man", not including people with additional abilities) in two dimensions and three dimensions, the potential for incorrectly perceiving (or, if you prefer, personal mental control of "seeing exactly what you want to see") is exponential. One reason so many dreams are composites is to (ironically) present more discernible layers although such a combined whole with either imagery or events may easily confuse the conscious mind (depending on the person and whatever lies they have absorbed from consensus or herd mentality - including nonsensical "dream dictionaries"). The laws of chance cease to mean anything if you already know the order of the cards in the deck.
I have been thinking of posting an entry on how some types of dreams are actually generated, but that might remove some of the "magic".