This took me a while to figure out. We no longer visit all 9 block
around and with the touched node, but instead visit adjacent plus
self. We then walk -non- recursively through all neigbors and if
they cause a nodeupdate, we just keep walking until it ends. On
the way back we prune the tail.
I've tested this with 8000+ sand nodes. Video result is here:
https://youtu.be/liKKgLefhFQ
Took ~ 10 seconds to process and return to normal.
2016-03-27 15:47:01: ERROR[Main]: ServerError: Lua: Runtime error from mod '*builtin*' in callback luaentity_Step(): Node name is not set or is not a string!
2016-03-27 15:47:01: ERROR[Main]: stack traceback:
2016-03-27 15:47:01: ERROR[Main]: [C]: in function 'add_node'
2016-03-27 15:47:01: ERROR[Main]: /usr/share/minetest/builtin/game/falling.lua:96: in function </usr/share/minetest/builtin/game/falling.lua:43>
Commit
65c09a96f41705bb8e75fc5ff4276342be91ed11 "Set acceleration only once in falling node"
has made the acceleration being set only once.
But this has introduced a regression.
Fix#3884.
