ludic/changes/render3d-island.md

bump: minor type: feat ludic.render3d: terrain_island(cx, cz, r, fall) keeps land out to r and then scales the terrain down into the water over fall metres. Scaling rather than blending to a fixed bed is what makes the coastline come out of the terrain already there: low ground becomes beach and shallows, high ground becomes cliff. r = 0 leaves the survey untouched.