Could you suggest what's exactly happening with bol here?

6:15 where car has been displaced from the BG, how do you think what are Channel Booleans are set to? also for the ground displace should we have a gradient mask? and what are the settings in the displace 3d tool? This is very technical set up in general you kind of see what's going on there but I wish there 'd be more explanation on such things. The technique itself is thrilling!

Nothing fancy, probably add or max (or subtract or min depending on the was the mask itself or the background is rendered).

It's basically how >90% of the 3D films are made today, by generating a depth map by masking.

Thanks! Even if it's a common thing among feature films, it's still new to me, wish to see an example of how the nodes are handled, if you have one would be helpful!