Hiya SS and all
Have you heard of the terming 'Phasing'? Robert Monroe used that term and from what I can tell by reading about it, it's basically a WILD.
I'm able to do it too...sadly not at will. It's near enough as you describe SS. However I don't need to be exhausted. Ordinarily I will already have had a good few hours of sleep and I'm lying in bed awake but very relaxed. If I manage to stay awake, I can watch myself fall asleep. The images come thick and fast at first and then one stops, expands and becomes stable. I can look around the image and it becomes three-dimensional...whereupon I am no longer looking at it, but in it, fully aware and awake.
It's pretty spectacular when it happens!
Squatch