From 5fb06e21903ff55852bbfe25034aecce52be7f82 Mon Sep 17 00:00:00 2001 From: madmaxoft Date: Wed, 4 Jun 2014 23:04:17 +0200 Subject: docs/Generator: Added the TerrainHeight section. --- docs/Generator.html | 54 +++++++++++++++++++++++++++++++++++++++++++ docs/img/biomalheights.jpg | Bin 0 -> 77747 bytes docs/img/biomeheights.jpg | Bin 0 -> 16432 bytes docs/img/biomeheightsavg.jpg | Bin 0 -> 14946 bytes 4 files changed, 54 insertions(+) create mode 100644 docs/img/biomalheights.jpg create mode 100644 docs/img/biomeheights.jpg create mode 100644 docs/img/biomeheightsavg.jpg diff --git a/docs/Generator.html b/docs/Generator.html index f6e7f1cd9..282e4c412 100644 --- a/docs/Generator.html +++ b/docs/Generator.html @@ -19,6 +19,7 @@ with specific implementation notes regarding MCServer.

  • Terrain height
  • Terrain composition
  • Finishers
    • +
  • Making it all faster

    • @@ -304,16 +305,69 @@ using the same approach as in MultiStepMap - by using a thresholded 2D Perlin no

    Terrain height

     +

    As with biomes, the easiest way to generate terrain height is not generating at all - assigning a constant +height value to all columns. This is again useful either for internal tests, and for worlds like MineCraft's +Flat world.

    + +

    For a somewhat more realistic landscape, we will employ the good old 2D Perlin noise. We can use it +directly as a heightmap - each value we get from the noise is stretched into the desired range (usually from +40 to 120 blocks for regular MineCraft worlds) and used as the height value. However, this doesn't play too +well with the biomes we've just generated. If the biome says "ocean" and the Perlin noise says "mountain", +the end result will be unpleasant.

    + +

    So we want a height generator that is biome-aware. The easiest way of doing this is to have a separate +generator for each biome. Simply use the biome map to select which generator to use, then ask the appropriate +generator for the height value. Again, this doesn't work too well - imagine an ExtremeHills biome right next +to an Ocean biome. If no extra care is taken, the border between these two will be a high wall. The following +image shows a 2D representation (for simplification purposes) of the problem:

    + + +

    This requires some further processing. What we need is for the terrain height to be dependent not only on +the immediate biome for that column, but also on the close surroundings of the column. This is exactly the +kind of task that averaging is designed for. If we take the area of 9x9 biomes centered around the queried +column, generate height for each of the biomes therein, sum them up and divide by 81 (the number of biomes +summed), we will be effectively making a 9-long running average over the terrain, and all the borders will +suddenly become smooth. The following image shows the situation from the previous paragraph after applying +the averaging process:

    + + +

    The approach used in MCServer's Biomal generator is based on this idea, with two slight modifications. +Instead of using a separate generator for each biome, one generator is used with a different set of input +parameters for each biomes. These input parameters modify the overall amplitude and frequency of the Perlin +noise that the generator produces, thus modifying the final terrain with regards to biomes. Additionally, the +averaging process is weighted - columns closer to the queried column get a more powerful weight in the sum +than the columns further away. The following image shows the output of MCServer's Biomal terrain height +generator (each block type represents a different biome - ocean in the front (stone), plains and ice plains +behind it (lapis, whitewool), extreme hills back right (soulsand), desert hills back left (mossy +cobble)):

    + + +

    One key observation about this whole approach is that in order for it to work, the biomes must be +available for columns outside the currently generated chunk, otherwise the columns at the chunk's edge would +not be able to properly average their height. This requirement can be fulfilled only by biome generators that +adhere to the second Expected property - that re-generating will produce +the same data. If the biome generator returned different data for the same chunk each time it was invoked, it +would become impossible to apply the averaging.

    + +

    (TODO: height with variations (N/A in MCS yet)

    Terrain composition

     +

    (TODO)

    Finishers

     +

    (TODO)

    + + +
    + +

    Making it all faster

     +

    (TODO)

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