No one really has a straight forward explanation for this kind of thing.
It happens in meditation and spontaneously sometimes, mostly at night though for me. Yesterday though something like this was going on, i could induce some flowing patterns by focusing. Right now i just woke up from a really freaky nap about spice and hyperspace. Everyone i'd ever known was popping out of the woodwork doing insanely uncharacteristic things..well not my resident assistant, at first he was trying to bust me in my own home for 'drugs' while impossibly beautiful alien bongs filled my closet, spice sculptures were on my desks, and it felt like i'd taken a huge dose of something. The RA seemed to completely forget about it a minute later. Relatives kept coming up to me asking if i had a problem with drugs, I never have, and I attempted to correct their stereotypical view of them to not much success. Someone must have spiked the punch with elf dust and maois because the scenes and people were changing so fast I couldn't make any sense of this strange party or remember much of it, most of what i remember just doesn't make any sense.
Then it turned into the real twilight zone. Someone heard a sound while coming in the back door, and turned around to see a white light. We all looked and walked out to see a huge train appearing in the distance from the back field behind my house, it was like the back to the future train sort of..it swerved in front of us then careened by the house and we heard an odd splash like it'd hit some body of water in the distance. We all walked toward the field where more colors and strange sounds started appearing at first there, then to the north, then the east. There were shooting stars everywhere. I could feel that onset feeling and I seriously thought hyperspace was starting to impinge and leak into our reality or something. That or we were all peaking really hard LOL XD. I was sort of worried for these people because they were all really scared and so was I. I can't remember anything after that.. I think i woke up then.
Sorry for flying off topic like a mad man.

I think i experienced something like what your talking about yesterday and it was just funny reading this after waking up from that dream, I had to post. The mind is a very strange place indeed!