Mapgen Carpathian: Reduce influence of 3D noise on mountains

[vlapsley]

Addresses issue #6349

Three minor changes to mountains:

• Remove 3D noise from the GetSteps function
• Hardcode the step width to 0.5 in the getSteps function.
• Lower persistence in the 3D noise variation for all mountains 0.6 -> 0.55 to reduce chance of floating blobs of stone

[paramat]

Reducing the influence of 3D noise may reduce floating stone, but it also reduces the chance of interesting shapes, arches, overhangs, so it's a difficult balance. I recommend not trying to completely avoid floating stuff. Persistence 0.55 is fairly smooth and not so good for interesting detail.

You have lots of time to tune the mapgen, 0.5 release is late December at the earliest. So feel free to keep making tuning PRs.
Are you sure you're happy with this? No rush.

[paramat]

Code is fine.

[paramat]

I would prefer that persistence is not reduced, but i'm +1 for all other changes.
Maybe leave tuning persistence to a later PR so that you can spend more time finding a balance?
So, i approve the PR if persistence is not reduced in this PR.

[paramat]

If you're sure about the persistence reduction then 👍

[SmallJoker]

Tested. The floating stones are gone - the mountains look smoother now. Found a few 3D overhangs, which haven't changed much from before/afterwards.
👍