Change how dirt turns to dirt_with_(something)

This changes how dirt blocks turn to dirt_with -grass, -dry_grass
or -snow.

Previously, dirt that was sunlit would turn to dirt_with_grass no
matter what, but this happened without any context, so you could
get green patches of dirt_with_grass in the middle of a savannah or
even desert.

Dirt no longer turns to covered dirt unless it's within 1 node from
another dirt_with_grass or dirt_with_dry_grass or dirt_with_snow.
This makes dirt_with_grass "growback" a lot slower, since it now only
happens on the edges, but it retains the context nicely now.

If there is any dirt with a grass or dry grass plant, or snow on top,
and enough light, we'll convert it sporadically to dirt_with_grass
or dirt_with_dry_grass or dirt_with_snow.

This allows us to plant grass of our choice in a large dirt patch,
or in a region where otherwise that type of grass is not present.

This used to be done by 2 abms, but I've combined them in to a single
ABM that is ordered to run with maximum efficiency, solving for the
most common outcome first before attempting more complex checks.

diff --git a/mods/default/functions.lua b/mods/default/functions.lua
index bd55d32fee873a217b92a6fd8c2abd7faa76b68c..775803bc611e6621511db0493d2b86854e1be6ee 100644 (file)
--- a/mods/default/functions.lua
+++ b/mods/default/functions.lua
@@ -353,32 +353,69 @@ minetest.register_abm({
 
 
 --
--- Grass growing on well-lit dirt
+-- Convert dirt to something that fits the environment
 --
 
 minetest.register_abm({
        nodenames = {"default:dirt"},
-       neighbors = {"air"},
+       neighbors = {
+               "default:dirt_with_grass",
+               "default:dirt_with_dry_grass",
+               "default:dirt_with_snow",
+               "default:grass_1",
+               "default:grass_2",
+               "default:grass_3",
+               "default:grass_4",
+               "default:grass_5",
+               "default:dry_grass_1",
+               "default:dry_grass_2",
+               "default:dry_grass_3",
+               "default:dry_grass_4",
+               "default:dry_grass_5",
+               "default:snow",
+       },
        interval = 6,
        chance = 67,
        catch_up = false,
        action = function(pos, node)
+               -- Most likely case, half the time it's too dark for this.
                local above = {x = pos.x, y = pos.y + 1, z = pos.z}
-               local name = minetest.get_node(above).name
-               local nodedef = minetest.registered_nodes[name]
-               if nodedef and (nodedef.sunlight_propagates or nodedef.paramtype == "light") and
-                               nodedef.liquidtype == "none" and
-                               (minetest.get_node_light(above) or 0) >= 13 then
-                       if name == "default:snow" or name == "default:snowblock" then
-                               minetest.set_node(pos, {name = "default:dirt_with_snow"})
-                       else
-                               minetest.set_node(pos, {name = "default:dirt_with_grass"})
+               if (minetest.get_node_light(above) or 0) < 13 then
+                       return
+               end
+
+               -- Look for likely neighbors.
+               local p2 = minetest.find_node_near(pos, 1, {"default:dirt_with_grass",
+                               "default:dirt_with_dry_grass", "default:dirt_with_snow"})
+               if p2 then
+                       -- But the node needs to be under air in this case.
+                       local n2 = minetest.get_node(above)
+                       if n2 and n2.name == "air" then
+                               local n3 = minetest.get_node(p2)
+                               minetest.set_node(pos, {name = n3.name})
+                               return
                        end
                end
+
+               -- Anything on top?
+               local n2 = minetest.get_node(above)
+               if not n2 then
+                       return
+               end
+
+               local name = n2.name
+               -- Snow check is cheapest, so comes first.
+               if name == "default:snow" then
+                       minetest.set_node(pos, {name = "default:dirt_with_snow"})
+               -- Most likely case first.
+               elseif name:sub(1, 13) == "default:grass" then
+                       minetest.set_node(pos, {name = "default:dirt_with_grass"})
+               elseif name:sub(1, 17) == "default:dry_grass" then
+                       minetest.set_node(pos, {name = "default:dirt_with_dry_grass"})
+               end
        end
 })
 
-
 --
 -- Grass and dry grass removed in darkness
 --