(https://imgur.com/a/mAG38BN) The number of underground water sources seeded is actually width x depth / 8000 (typo?). The number of tree patches is actually width x depth / 4000 (forgot to remove height after copying and pasting?). Also, the "Eroding..." step seems to be missing. I can't figure out how it works, though, so you will have to pick variable names.

Minecraft-Classic-map-generation-algorithm.md

@@ -26,6 +26,7 @@ Where x, y are the given 2D coords and noise1, noise2 are the two noise function
 Generation of a Classic Minecraft map, as seen on the sadly defunct browser-embedded version of creative mode that used to be hosted on the main Minecraft site, goes through a sequence of generation steps each time a new map is created:
 * choose map size
 * create height-map, _"Raising..."_
+* smooth out height-map, _"Eroding..."_
 * create strata, _"Soiling..."_
 * carve out caves, _"Carving..."_
 * create ore veins
@@ -67,6 +68,22 @@ If heightResult < 0 {
 heightMap(x,z) is then set to the integer component of heightResult + waterLevel.
 ```
 
+## Smooth out height-map
+
+Using:
+* noise1, a combined noise function with two octave noise functions (of octave 8) as input.
+* noise2, a combined noise function with two octave noise functions (of octave 8) as input.
+
+For each column in the x,z plane assign a new elevation value to heightMap computed from:
+```
+Let a be noise1.compute( x*2, z*2) / 8
+Let b be 1 if noise2.compute( x*2, z*2) > 0, otherwise 0
+
+If a > 2 {
+    heightMap(x,z) is then set to: (int)((heightMap(x,z) - b) / 2) * 2 + b
+}
+```
+
 ## Create strata
 
 Using:
@@ -185,7 +202,7 @@ for len in veinLength {
 Water is flood-filled into the map, spreading horizontally and down vertically, from the x,z edges of the map at a height of water level - 1. 
 
 Some underground water sources are then added to the block array to create flooded caves. The number seeded is:
-width x depth / 800
+width x depth / 8000
 
 For each water source a random x and z coordinate value is chosen and the y coordinate is set to water level - 1, or water level - 2. If this position in the block array is AIR then the water flood-fills out and downwards.
 
@@ -280,7 +297,7 @@ Repeat 20 times {
 
 ### Trees
 
-Finally trees are added to the map, there will be width x height x depth / 4000 patches of trees created.
+Finally trees are added to the map, there will be width x depth / 4000 patches of trees created.
 
 For each tree patch:
 ```