MinecraftForge/MinecraftForge — pull request #491 by fabricator77 (2013-03-29 04:14:45+00:00)
Title: Fixes cave generation to work with mod biomes

Caves generated by MapGenCaves will currently not cut through custom
topBlocks, which causes caves to stop 1 block below the surface. This
fixes the behaviour and as a bonus also fixes cavegen in vanilla
mushroom biomes.