This reverts commit ec7b481170.
This was wrong, `d` is not a distance but the `d` constant in the
parametric equation `ax + by + cz = d` describing the plane.
Happy new year to the wonderful Godot community!
We're starting a new decade with a well-established, non-profit, free
and open source game engine, and tons of further improvements in the
pipeline from hundreds of contributors.
Godot will keep getting better, and we're looking forward to all the
games that the community will keep developing and releasing with it.
