check this video out. [link] the main thing to know is .rotationX, ..Y, ..Z. So pretend a movieclip is a plane and then you can build things as basic rooms and boxes. Trying to do something like characters I don't see it with this method. There are no cameras so you have to move the whole container of your 3d scene.
I can't find the source files... If you're planning on making a game I suggest you try this [link] I didn't use this because at the time it wasn't available. Now it is available, though if you want to make a 3d demo only people with the flash player 11 beta can see until it gets released to the masses.
you should generate your rays by tracing through a "plane" (line in 2d) in front of the camera point; from looking at the results here, it seems you're just stepping at a constant angle within the field of view.