Terrain generation design

[adamhutchings]

The process right now can get away with being strictly column-based because we are doing nothing more than generate voxels in columns (bedrock, stone, dirt, grass), but with the addition of later features (trees and lakebeds at first, biomes later) they will certainly be more complicated than that. What should the pipeline look like?

[mileskerr]

we have to do it in at least two passes.

• first pass, generate terrain based of heightmap columns
• second pass, populate it with trees, ores, whatever (i'm calling this stuff terrain scatter)

the difficult part is generating terrain scatter that crosses over a chunk border. you can't put terrain scatter on terrain that doesn't exist, so my thought is that for each chunk, we wait to do the second pass until the first pass is done for all the surrounding chunks. that means for each chunk will generally end up going through these four stages:

1 - chunk goes through first pass. no scatter yet.
2 - chunk gets some scatter that crossed the border from neighboring chunks going through their second pass.
3 - chunk goes through second pass (all neighboring chunks have finished at least their first pass, but their second passes will probably not all be complete at this point)
4 - the remaining neighboring chunks go through their second pass, meaning all scatter that could cross into this one is generated. the chunk is fully generated.

[mileskerr]

of course we'd also need a third pass to carve caves into the terrain. that would probably go between passes 1 and 2 but i think we cross that bridge when we get there.