a couple of weeks after the demo was released, people found out that the tree scene wasn't rendered in realtime! Kalms (the coder) confirmed this later. Nevertheless it's a fantastic demo (which works perfectly with WinUAE, by the way. I'm always using a plain WB 3.1 for getting demos to work, with no extra stuff installed). Other "modern" demos from TBL, which are worth looking: Magia (2003), Contour (1999), Little Nell (2002), Rain (1999). You can download them here: http://www.back2roots.org/Demos/Files/Black%20Lotus/
Also you might be interested in watching a 64k intro from the group Loonies which is called "PC 64k". Even if the name sounds strange, it's an Amiga production. This little intro shows nearly the same tree scene as in the TBL demo, but this time it IS rendered in realtime. You can get the demo here: http://www.back2roots.org/Demos/Files/Loonies/
. This intro was coded to impress the TBL guys ;-).