Pregenerated Islandising Of Terrain
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Making islands also covers the erosive forces of the ocean. We need to raise some ground and then erode the crap out of everything below sea level.


Island Map

I use an island map. I've tried a few different techniques, but using the posteriser keeps my code standardised.


A random terrain with a posterised height map.



Erosion

We now have to make beaches, eroding terrain and exposing rock. The erosion process is similar to the rain erosion in the rain page. Thinking mechanically, the ocean comes up onto land, grabs some of the terrain and pulls it back into the ocean. Everything gets smoothed, even rock, though not as quickly. We need a high tide level and simply do a height check for every texel. If it is below high tide, then a portion of the terrain is migrated towards the ocean. Erode neighbouring texels too, to emulate water battering the land. The higher the tide mark (ie how far above sea level you erode), the more beach front you'll end up with.


Coastal erosion just pulls all silt below high tide mark into the ocean.



So far terrain on the shore line is left forming cliffs. The more iterations, the more cliffs are formed. The rain erosion will take care of flattening the silt, leaving cliffs of exposed rock.






Conclusion

Fairly straight forward.

Next:Adding sensible rivers


Email teatreetim@yahoo.com.au for questions. Please don't ask me for source code, but I may do pseudo code for sections if there's interest.