I remember onetime I was up in Oregon and before I feel asleep I looked up at the ceiling and it seemed to be moving or waving, almost breathing, and no there were no drugs involved. I think the mind does interesting things as you fall asleep. Ive always found that I have a rush of ideas before I dose off, like I subconsciously cant stop thinking about events in my life. Its very weird. I can relate to what you mean by very clear. I doubt you were having a dream but rather your mind was as I would put it decompressing or something of that sort. Fun stuff!