Under the hood, biomes will be assigned to each tile of a map during generation. That biome will then determine what ground, trees and decoration will be used / spawned for that tile. Biome information will only be used during map generation and will not be stored in the map.
Biomes itself are implemented in a way that should make it possible for plugin creators to extend the system in the future.
There will be two types of biomes, one for land and one for water. The type will be selected based on the terrain height that will be generated before biomes will be applied. For now there is no use for water biomes.
Given a tile and a list of possible biomes the actual biome will be selected based on a relative probability p that will be calculated for each biome. The biome of the highest probability will be used.
Biome parameters
These are the parameters a biome can specify that will determine where the biome will be used. All of these are floats. The default values are specified after the colon.
As a rule of thumb you should aim for the following equation to be true:"noise scale": 1 (bigger values mean bigger noise pattern)
"noise offset": 0
"noise factor": 0 (usually in 0..1 with 0 meaning no noise contribution)
"noise variance": 1 (bigger values will basically splatter the noise sampling for more spread out biome edges)
"noise seed": random (integer value used as a seed to control the noise function, a random number by default; can be used to enforce the same noise on multiple spawn definitions)
"height center": 0 (the target height where contribution should be max)
"height radius": 1 (the radius of where height should contribute)
"height offset": 0
"height factor": 0 (usually in 0..1 with 0 meaning no height contribution)
"deriv center": 0 (the target steepness where contribution should be max)
"deriv radius": 1 (the target variance from target steepness that should contribute)
"deriv offset": 0
"deriv factor": 0 (usually in 0..1 with 0 meaning no height contribution)
"offset": 0 (overall probability offset)
"coverage": 1 (e.g. 0.5 would make appearance less likely)
"precedence": 1 (overall multiplier, e.g. useful for making sparse tree / decoration spawning)
\(
\begin{equation}
noise\_factor + height\_factor + deriv\_factor + offset \leq 1
\end{equation}
\)
This ensures that a biome does not completely displace another one.
Tile input parameters
These are the tile dependent parameters that will be used to evaluate the likelihood of a biome. They are mentioned here for completeness.
- x (integer, 0..<width of the city)
- y (integer, 0..<height of the city)
- height (float, zero being coast line, snow usually starts at height 5)
- steepness (float, ranges from 0 to 1)
The formula
Biome probability p for a tile (x, y, height, steepness):
You can consider the noise(x, y, noise_scale, noise_variance, noise_seed) as doing some magic for you that outputs a nice noise distribution using Perlin noise. A different noise distribution will be used for each biome unless a noise_seed was defined explicitly.\(
\begin{align}
n :=& noise(x, y, noise\_scale, noise\_variance, noise\_seed) + noise\_offset \\
h :=& 1 - \frac{|height - height\_center|}{height\_radius} + height\_offset \\
d :=& 1 - \frac{|steepness - deriv\_center|}{deriv\_radius} + deriv\_offset \\
p :=& precedence \cdot \left( \frac{noise\_factor \cdot n + height\_factor \cdot h + deriv\_factor \cdot d + offset - 1}{coverage} + 1 \right)
\end{align}
\)
The minimum p for the default biome is 0.1 so if the probability of all other biomes is smaller than 0.1 the default biome will be used.
Example
For example the coast biome uses the following definition to spawn near the water only:
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[ { "id": "$biome_coast00", "type": "biome", "noise scale": 1, "noise offset": 0.5, "noise factor": 0.5, "noise variance": 2, "height center": 0, "height radius": 0.05, "height factor": 1, "offset": -0.5 } ]
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Ground spawning
We want to spawn ground dependent on the biome. To do so, we can either define the biomes to spawn in in the ground object:
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"biome": ["$mybiomeid", ...]Code: Select all
"grounds": ["$mygroundid", ...]Tree and decoration (building) spawning
This works like for ground. In a tree or building definition you can write:
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"biome": ["$mybiomeid", ...]Code: Select all
"tree": ["$mytreeid", ...],
"building": ["$mybuildingid", ...]Biome Ids
In case you want your ground / tree / building to be spawned in one of the pre-defined biomes you have to specify the spawning behavior in it as well as you cannot easily extend an existing biome (it's possible though by using inherit). So here's a list of the pre-made biomes so you can hook into them:
- $biome_ocean00 (this is the only water biome for now and having multiple is not yet supported)
- $biome_aspen_forest00
- $biome_deciduous_forest00
- $biome_coniferous_forest00
- $biome_mixed_forest00 (this is the default land biome in case auto spawn for a tree was set)
- $biome_boreal_forest00
- $biome_redwood_forest00
- $biome_desert00
- $biome_snow00
- $biome_rainforest00
- $biome_coast00
- $biome_grassland00
- $biome_steppe00
- $biome_flowerygrassland00
- $biome_sakura00
Spawn parameters for ground, tree and building
Like for biomes you can use the presented Biome parameters also in the context of spawn definitions for more variety. In a biome this may look like
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"ground": [{
"id": "$mygroundid",
... // Spawn parameters
}],
"tree": [{
"id": "$mytreeid",
... // Spawn parameters
}],
"building": [{
"id": "$mybuildingid",
... // Spawn parameters
}]Example: Candy Land (sugar is unhealthy, don't eat too much of it)
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[ { "id": "$ground_candy00", "type": "ground", "template": "$template_ground", "blending": false, "frames": {"bmp": "ground.png", "handle y": 9}, "border frames": {"bmp": "ground.png", "handle y": 9, "copies": 15}, "map color": {"r": 255, "g": 220, "b": 240} }, { "id": "$tree_candy00", "type": "tree", "frames": {"bmp": "candy.png", "w": 32, "count": 4}, "map color": {"r": 220, "g": 80, "b": 80} }, { "id": "$biome_candy00", "type": "biome", "title": "Candy Land", "preview frames": {"bmp": "preview.png", "handle y": 0}, "noise factor": 1, "noise scale": 4, "coverage": 0.3, "ground": ["$ground_candy00"], "tree": { "id": "$tree_candy00", "noise factor": 1, "noise scale": 0.5, "deriv factor": 1, "deriv radius": 0.5, "offset": -1, "precedence": 0.3 } } ]
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For reference, this is how it would look like if the biome was defined first (i.e. because it is part of the game):
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[ { "id": "$biome_candy00", "type": "biome", "title": "Candy Land", "preview frames": {"bmp": "preview.png", "handle y": 0}, "noise factor": 1, "noise scale": 4, "coverage": 0.3 }, { "id": "$ground_candy00", "type": "ground", "template": "$template_ground", "blending": false, "frames": {"bmp": "ground.png", "handle y": 9}, "border frames": {"bmp": "ground.png", "handle y": 9, "copies": 15}, "map color": {"r": 255, "g": 220, "b": 240}, "biome": ["$biome_candy00"] }, { "id": "$tree_candy00", "type": "tree", "frames": {"bmp": "candy.png", "w": 32, "count": 4}, "map color": {"r": 220, "g": 80, "b": 80}, "biome": { "id": "$biome_candy00", "noise factor": 1, "noise scale": 0.5, "deriv factor": 1, "deriv radius": 0.5, "offset": -1, "precedence": 0.3 } } ]
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candy_land.zip- (4.68 KiB) Downloaded 76 times
Ivano-Frankivsk, Ukraine
