Performance problems in the cave biome map generator when there is a large difference in total chances between different layers of depth.

[IntegratedQuantum]

The generator currently selects biomes randomly (using a slow linear algorithm), checks if they fit into the depth range, and discards them if not available. This can be pretty bad if one region has significantly higher chances (this may happen if an addon wants to replace all natural biomes in region, by setting the chances of its own biomes to 100000000).

I think a better solution would be to use a tree with a node for all distinct depth ranges, containing one precomputed alias table each.