(Release 566) Z tearing when floor is built over slab

Building floors built on top of a slab cause both the floor and the slab to render over each other.

Steps to reproduce:

  1. Build a slab
  2. Build a building such that the floor should replace the slab. This screenshot came from using a saved building, but I tried it with creating a new building and had the same result.
  3. Watch the Z fighting disco insanity.

Expected Results:
The hearthlings should either remove and replace the slab, or the slab should just stop being rendered.

Actual Results:
Both the slab and new floor interleave.

Version Number and Mods in use:
Release 566, debug tools

Also occured in A16 (though there you could use ‘Remove’ to deconstruct the slab-floor after the foundation/road were build - seemed like it should’ve broken something, but it worked fine in my experience) and in earlier A17 dev releases.

(you can still console-command ‘destroy’ the slab floor as a workaround, if the z-fighting gets too annoying).

I do agree with the ‘expected results’ - I had presumed the foundation/road would have stopped the underlayer from rendering, or have removed the slab underlayer much as hearthlings mine out the ground for a ‘normal’ foundation/road. The latter seems most ‘consistant’ with the world, but the former seems to match better with the general "hearthling-built structures are nigh invulnerable’ motif.