Minecraft-style lavacasting involves making a lavafall and pouring water
over it to solidify the flowing lava. The Minetest engine make this hard
to do, since water that flows beside lava flows at similar speed as lava
disappaers. Therefore, making a lava curtain and pouring water over that
can not create a solid wall of cobblestone as it does in Minecraft if no
code is added to speed up downwards water flow.
This patch adds an ABM that speeds up downwards water flows, turning any
lava nodes next to the newly spawned water into cobblestone or obsidian.
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