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0010897Dwarf FortressDwarf Mode -- Environmentpublic2018-09-14 10:072018-09-16 12:19
Adequate Swimmer 
Win 7
0010897: Soil floor/ceiling can randomly disappear after a long period of time
If there is a dug out room under a soil tile, the tile has a chance to disappear (self-channel) over a long time period, revealing the room directly below it to outside.

The issue only affects tiles that have sunlight above them and a dug out room directly under them.
Does not seem to be affected by external factors. The missing tiles will always create a random noise pattern, regardless of traffic, weather or other activity.

Will work for soil, not tested with sand, solid rock or other materials.
Does not affect constructed floors/ceilings.
Possibly related to the bug that transports teeth and arrows through z-levels.
1. dig out and mark a stockpile directly below the ground level
2. mark the stockpile as a burrow to make the holes more easily visible when they appear
3. alternatively make an entire small fort directly below the ground and let it run in the background until bits of ceiling start falling off. This is easier to notice since dwarves vomit when suddenly hit by sunlight
4. it takes a year for the first hole to show up, after that the ceiling slowly degrades in the exact same manner as an isotope.
May be a useful "feature" in megaprojects, for creating noise patterns, timers, increasing flows or for a crude form of random number generation.
feature, floor, soil, z-levels
Issue History
2018-09-14 10:07Adequate SwimmerNew Issue
2018-09-14 10:08Adequate SwimmerTag Attached: feature
2018-09-14 10:09Adequate SwimmerTag Attached: floor
2018-09-14 10:09Adequate SwimmerTag Attached: z-levels
2018-09-14 10:09Adequate SwimmerTag Attached: soil
2018-09-15 02:21PatrikLundellNote Added: 0038802
2018-09-15 10:07LociNote Added: 0038804
2018-09-15 10:07LociAssigned To => Loci
2018-09-15 10:07LociStatusnew => needs feedback
2018-09-16 12:19Adequate SwimmerNote Added: 0038807
2018-09-16 12:19Adequate SwimmerStatusneeds feedback => assigned
2018-09-16 12:31Adequate SwimmerNote Edited: 0038807bug_revision_view_page.php?bugnote_id=0038807#r15778
2018-09-16 12:40Adequate SwimmerNote Edited: 0038807bug_revision_view_page.php?bugnote_id=0038807#r15779

2018-09-15 02:21   
It is a known issue that hole appear when trees are cut down if there is a room immediately beneath the tree. Thus, if there is a random hole creation process in play it's hard to distinguish it from the known cause of holes.

I've had occasional holes appear, but I've had little reason not to assume they are the results of cutting trees, although I've had cases that surprised me, as I'd thought I'd made dirt roads to block trees from maturing.

Proving it's not caused by logging is tricky:
- If you can get it to happen in a desert with too little rain to support trees, that would be ideal.
- Regularly making dirt road above any vulnerable locations should keep trees away, but it's easy to forget to renew them. As it takes 3 years for a sapling to renew, the dirt road interval has to be shorter than 3 years.
- A stockpile (even with nothing allowed to be stored in it) blocks the maturation of trees and does not have to be renewed. If a hole appears under such a stockpile it would probably prove there is a random hole making process in play, but it's not impossible a stockpile might interfere with such a process even if there is one, so absence of holes under a stockpile would not prove that no such process might exist.
- Changing the raws to not allow for any trees, or at least no trees in the biome area you intend to perform the experiment in would work well too. You could have a functional fortress with logging if the embark contained one tree less experiment biome and one normal biome (and obviously made the experiment in the tree less part).
- Never perform any logging at all over the experiment area. This includes cutting down trees that are in the way or with gobbo bits stuck in the branches.
2018-09-15 10:07   
Were you woodcutting on the surface?
Adequate Swimmer   
2018-09-16 12:19   
(edited on: 2018-09-16 12:40)
The part of the surface where it happened didn't have trees or logging for a while (1-2 yrs), I wanted to see if holes will keep appearing.

I will try to make an embark at the edge of a desert using the suggestions above and see if I can get ... evidence of absence.