244 lines
9.6 KiB
Markdown
244 lines
9.6 KiB
Markdown
---
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title: Biomes and Decorations
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author: Shara
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layout: default
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root: ../..
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idx: 6.1
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description: Create biomes and decorations to customise the map
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---
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## Introduction <!-- omit in toc -->
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The ability to register biomes and decorations is vital when aiming to create an
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interesting and varied in-game environment. This chapter teaches you how to
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register biomes, how to control biome distribution, and how to place decorations in biomes.
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- [What are Biomes?](#what-are-biomes)
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- [Biome Placement](#biome-placement)
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- [Heat and Humidity](#heat-and-humidity)
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- [Visualising Boundaries using Voronoi Diagrams](#visualising-boundaries-using-voronoi-diagrams)
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- [Creating a Voronoi Diagram using Geogebra](#creating-a-voronoi-diagram-using-geogebra)
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- [Registering a Biome](#registering-a-biome)
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- [What are Decorations?](#what-are-decorations)
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- [Registering a Simple Decoration](#registering-a-simple-decoration)
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- [Registering a Schematic Decoration](#registering-a-schematic-decoration)
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- [Mapgen Aliases](#mapgen-aliases)
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## What are Biomes?
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A Minetest biome is a specific in-game environment. When registering biomes, you
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can determine the types of nodes that appear in them during map generation.
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Some of the most common types of node that may vary between biomes include:
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* Top node: This is the node most commonly found on the surface. A well-known
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example would be "Dirt with Grass" from Minetest Game.
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* Filler node: This is the layer immediately beneath the top node.
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In biomes with grass, it will often be dirt.
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* Stone node: This is the node you most commonly see underground.
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* Water node: This is usually a liquid and will be the node that appears
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where you would expect bodies of water.
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Other types of node can also vary between biomes, providing an opportunity
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to create vastly different environments within the same game.
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## Biome Placement
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### Heat and Humidity
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It is not enough to simply register a biome; you must also decide where it can
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occur in game. This is done by assigning a heat and a humidity value to each biome.
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You should think carefully about these values; they determine which biomes can
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be neighbours to each other. Poor decisions could result in what is meant to
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be a hot desert sharing a border with a glacier, and other improbable
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combinations which you may prefer to avoid.
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In game, heat and humidity values at any point of the map will usually be between
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0 and 100. The values gradually change, increasing or decreasing as you move
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around the map. The biome at any given point will be determined by which of the
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registered biomes has heat and humidity values closest to those at that position on the map.
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Because the changes in heat and humidity are gradual, it is good practice to assign
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heat and humidity values to biomes based on reasonable expectations about that
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biome’s environment. For example:
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* A desert might have high heat and low humidity.
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* A snowy forest might have low heat and a medium humidity value.
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* A swamp biome would generally have high humidity.
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*
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In practice, this means that, as long as you have a diverse range of biomes, you
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are likely to find that the biomes which border each other form a logical progression.
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### Visualising Boundaries using Voronoi Diagrams
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<figure class="right_image">
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<img src="{{ page.root }}/static/biomes_voronoi.png" alt="Vernoi">
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<figcaption>
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Voronoi diagram, showing the closest point.
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<span class="credit">By <a href="https://en.wikipedia.org/wiki/Voronoi_diagram#/media/File:Euclidean_Voronoi_diagram.svg">Balu Ertl</a>, CC BY-SA 4.0.</span>
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</figcaption>
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</figure>
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Fine-tuning heat and humidity values for biomes is
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easier if you can visualise the relationship between the biomes you are using.
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This is most important if you are creating a full set of your own biomes, but
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can also be helpful if you are adding a biome to an existing set.
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The simplest way to visualise which biomes may share borders is to create a
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Voronoi diagram, which can be used to show which point on a 2-dimensional
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diagram any given position is closest to.
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A Voronoi diagram can reveal where biomes that should border each other do not,
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and where biomes that should not border each other do. It can also give a
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general insight into how common biomes will be in-game, with larger and more
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central biomes being more common than smaller biomes or biomes that are located
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on the outer edge of the diagram.
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This is done by marking a point for each biome based on heat and humidity values,
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where the x-axis is heat and the y-axis is humidity. The diagram is then
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divided into areas, such that every position in a given area is closer to the
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point inside that area than it is to any other point on the diagram.
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Each area represents a biome. If two areas share a border, the biomes they
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represent in-game can be located next to each other. The length of the border
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shared between two areas, compared to the length shared with other areas, will
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tell you how frequently two biomes are likely to be found next to each other.
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### Creating a Voronoi Diagram using Geogebra
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As well as drawing them by hand, you can also create Voronoi diagrams using
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programs such as [Geogebra](https://www.geogebra.org).
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1. Create points by selecting the point tool in the toolbar (icon is a point with 'A'),
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and then clicking the chart. You can drag points around or explicitly set their
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position in the left sidebar. You should also give each point a label, to make things clearer.
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1. Next, create the voronoi by entering the following function into the
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input box in the left sidebar:
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```cpp
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Voronoi({ A, B, C, D, E })
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```
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Where the each point is inside the curly brackets, separated by commas. You should now
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3. Profit! You should now have a voronoi diagram with all draggable points.
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## Registering a Biome
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The following code registers a simple biome named grasslands biome:
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```lua
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minetest.register_biome({
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name = "grasslands",
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node_top = "default:dirt_with_grass",
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depth_top = 1,
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node_filler = "default:dirt",
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depth_filler = 3,
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y_max = 1000,
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y_min = -3,
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heat_point = 50,
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humidity_point = 50,
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})
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```
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This biome has one layer of Dirt with Grass nodes on the surface, and three layers
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of Dirt nodes beneath this. It does not specify a stone node, so the node defined
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in the mapgen alias registration for `mapgen_stone` will be present underneath the dirt.
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There are many options when registering a biome, and these are documented
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in the [Minetest Lua API Reference](https://minetest.gitlab.io/minetest/definition-tables/#biome-definition),
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as always.
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You don’t need to define every option for every biome you create, but in some cases failure
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to define either a specific option, or a suitable mapgen alias, can result in map generation errors.
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## What are Decorations?
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Decorations are either nodes or schematics that can be placed on the map at mapgen.
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Some common examples include flowers, bushes, and trees. Other more creative uses
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may include hanging icicles or stalagmites in caves, underground crystal formations,
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or even the placement of small buildings.
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Decorations can be restricted to specific biomes, by height, or by which nodes
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they can be placed on. They are often used to develop the environment of a biome
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by ensuring it has specific plants, trees or other features.
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## Registering a Simple Decoration
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Simple decorations are used to place single node decorations on the map during
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map generation. You must specify the node that is to be placed as a decoration,
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details for where it can be placed, and how frequently it occurs.
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For example:
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```lua
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minetest.register_decoration({
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deco_type = "simple",
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place_on = {"base:dirt_with_grass"},
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sidelen = 16,
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fill_ratio = 0.1,
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biomes = {"grassy_plains"},
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y_max = 200,
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y_min = 1,
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decoration = "plants:grass",
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})
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```
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In this example, the node named `plants:grass` will be placed in the biome named
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grassy_plains on top of `base:dirt_with_grass` nodes, between the heights of `y = 1` and `y = 200`.
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The fill_ratio value determines how frequently the decoration appears, with higher
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values up to 1 resulting in a great number of decorations being placed. It is possible
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to instead use noise parameters to determine placement.
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## Registering a Schematic Decoration
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Schematic decorations are very similar to simple decoration, but involve the placement
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of a schematic instead of the placement of a single node. For example:
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```lua
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minetest.register_decoration({
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deco_type = "schematic",
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place_on = {"base:desert_sand"},
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sidelen = 16,
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fill_ratio = 0.0001,
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biomes = {"desert"},
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y_max = 200,
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y_min = 1,
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schematic = minetest.get_modpath("plants") .. "/schematics/cactus.mts",
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flags = "place_center_x, place_center_z",
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rotation = "random",
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})
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```
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In this example the cactus.mts schematic is placed in desert biomes. You need to provide
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a path to a schematic, which in this case is stored in a dedicated schematic directory within the mod.
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This example also sets flags to center the placement of the schematic, and the rotation
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is set to random. The random rotation of schematics when they are placed as decorations
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helps introduce more variation when asymmetrical schematics are used.
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## Mapgen Aliases
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Existing games should already include suitable mapgen aliases, so you only need
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to consider registering mapgen aliases of your own if you are making your own game.
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Mapgen aliases provide information to the core mapgen, and can be registered in the form:
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```lua
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minetest.register_alias("mapgen_stone", "base:smoke_stone")
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```
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At a minimum you should register:
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* mapgen_stone
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* mapgen_water_source
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* mapgen_river_water_source
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If you are not defining cave liquid nodes for all biomes, you should also register:
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* mapgen_lava_source
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