Builtin/../falling: Fix bugs caused by 'ignore' nodes

Original commit by t4im, rebased and developed by paramat.
Fix CONTENT_IGNORE being replaced by falling nodes or causing large
areas of sand to collapse into itself.
Format some conditional code for clarity.
Add and clarify some comments.

diff --git a/builtin/game/falling.lua b/builtin/game/falling.lua
index 5244ee782d72ca2fce952b254270b1665a2561df..1932b170aa751560b31fa6db4a69c82d089d2b03 100644 (file)
--- a/builtin/game/falling.lua
+++ b/builtin/game/falling.lua
@@ -46,15 +46,17 @@ core.register_entity(":__builtin:falling_node", {
                if not vector.equals(acceleration, {x = 0, y = -10, z = 0}) then
                        self.object:setacceleration({x = 0, y = -10, z = 0})
                end
-               -- Turn to actual sand when collides to ground or just move
+               -- Turn to actual node when colliding with ground, or continue to move
                local pos = self.object:getpos()
-               local bcp = {x = pos.x, y = pos.y - 0.7, z = pos.z} -- Position of bottom center point
-               local bcn = core.get_node(bcp)
-               local bcd = core.registered_nodes[bcn.name]
-               -- Note: walkable is in the node definition, not in item groups
-               if not bcd or bcd.walkable or
+               -- Position of bottom center point
+               local bcp = {x = pos.x, y = pos.y - 0.7, z = pos.z}
+               -- Avoid bugs caused by an unloaded node below
+               local bcn = core.get_node_or_nil(bcp)
+               local bcd = bcn and core.registered_nodes[bcn.name]
+               if bcn and
+                               (not bcd or bcd.walkable or
                                (core.get_item_group(self.node.name, "float") ~= 0 and
-                               bcd.liquidtype ~= "none") then
+                               bcd.liquidtype ~= "none")) then
                        if bcd and bcd.leveled and
                                        bcn.name == self.node.name then
                                local addlevel = self.node.level
@@ -154,16 +156,19 @@ function nodeupdate_single(p)
        local n = core.get_node(p)
        if core.get_item_group(n.name, "falling_node") ~= 0 then
                local p_bottom = {x = p.x, y = p.y - 1, z = p.z}
-               local n_bottom = core.get_node(p_bottom)
-               local d_bottom = core.registered_nodes[n_bottom.name]
-               -- Note: walkable is in the node definition, not in item groups
+               -- Only spawn falling node if node below is loaded
+               local n_bottom = core.get_node_or_nil(p_bottom)
+               local d_bottom = n_bottom and core.registered_nodes[n_bottom.name]
                if d_bottom and
+
                                (core.get_item_group(n.name, "float") == 0 or
-                                       d_bottom.liquidtype == "none") and
+                               d_bottom.liquidtype == "none") and
+
                                (n.name ~= n_bottom.name or (d_bottom.leveled and
-                                       core.get_node_level(p_bottom) < core.get_node_max_level(p_bottom))) and
-                               (not d_bottom.walkable or
-                                       d_bottom.buildable_to) then
+                               core.get_node_level(p_bottom) <
+                               core.get_node_max_level(p_bottom))) and
+
+                               (not d_bottom.walkable or d_bottom.buildable_to) then
                        n.level = core.get_node_level(p)
                        core.remove_node(p)
                        spawn_falling_node(p, n)