Low-disruption first step towards removing the hardcoded cave liquid
code. Since MT 5.0.0 cave liquids can be defined and located by
biome definitions instead.
In games that do not yet use biome definitions to define and locate
cave liquids (MTGame does), lava will now appear below
y = water_level - 256 instead of below 'lava depth' (usually y = -256).
Therefore no change in most mapgens if using the default 'lava depth'.
The upstream JsonCpp project has renamed the `json/features.h` file to
`json/json_features.h`. This patch fixes the JsonCpp installation search
by looking for `json/allocator.h` which has not been renamed on newer
versions of JsonCpp.
Fixes: https://github.com/minetest/minetest/issues/9119
Previously, the only way to disable the 3D noise tunnels was to set
'cave width' > 1.0, however doing so did not disable the very intensive
noise calculations or the generation loop.
All the other types of cave generation (randomwalk caves, caverns)
can already be independently and completely disabled.
This feature is now needed more because the small randomwalk caves are
now available for use as an alternative to the 3D noise tunnels.
Add mapgen parameters to set the range of the random number of
randomwalk caves per mapchunk, and to set the proportion that are
flooded with liquids.
Default values are, for now, unchanged from the previous hardcoded
values.
Add parameters to allow small randomwalk caves
Disabled by default for now as they have never been present in the
non-mgv6 mapgens.
Revert gamma upper limit to 3.0 because that was raised based on
a misunderstanding and had no benefit. A sane upper limit is
needed as players on a competitive server tend to use the maximum.
Set gamma lower limit to 0.33 for consistency with 3.0.
Set sane limits on alpha, beta, boost and enforce these in code
to limit values entered in minetest.conf and to avoid easy cheating
by editing settingtypes.txt.
Improve documentation and 'readable' setting names.
Clarify that gamma does not significantly affect natural night light.
light.cpp: Various codestyle and comment improvements.
