Biomes are the animal and plant life, soil properties and other natural elements that you would expect in an outdoors area according to its climate - a desert biome consists of sand, cacti and scorpions for example.
When designing virtual landscapes with Gaia, Biomes can be used to collect spawners that fit well together into an overarching biome. To create an ice biome, you could collect an ice texture spawner, an icy rock spawner, a snowman spawner in an Ice World Biome. You can then either spawn this biome across the entire terrain, or only e.g. in the lower left corner of the terrain.
Grouping Spawners into a biome is also useful to apply a matching set of spawners to a new terrain quickly - with the click of a button a terrain can receive a certain look and feel since all the spawning rules will adapt to the new terrain surface.

Here is the same terrain, but populated with a different biome each:


The tool that holds those spawners together and controls where they spawn in the Game World is the Biome Controller:



Similar to an individual spawner, the biome controller has multiple panels that control its functionality. The following sections describe the panels one by one.


Biome Settings



The Biome Settings panel holds some general settings for the biome, especially in regards to where it should be applied. The single settings are:


NameName of the biome. Changing the name here will also change the name in the hierarchy accordingly.
Spawner RangeControls the range of the biome spawn when spawning in "Area: Local" mode (see "Biome Spawners" panel below)
Sea LevelSets the height of the sea level in the scene - note that spawners usually spawn dependent on the sea level, changing this value can have great impact on the overall look of the scene.
Global Spawn DensityMultiplicator value for the density for all the spawners in the scene - increasing this value will result in more objects being spawned - this usually looks better, but has an impact on spawning times and runtime performance. Note that this is one global value for all spawners, changing this here will change it for all other biome controllers, spawners, etc. in the scene just like for the sea level.
VisualizationShows a preview for where the biome will be spawned on the terrain(s) according to the masks in the mask list below. The eye icon button activates / deactivates the visualization, while the color selection field allows you to select the color for the visualization.
Just like with the spawners you can add masks to the biome controller to restrict where it is allowed to spawn and where not. Please see the article on masking for this, it has more in-detail information about masks and also how masks are being inherited from biome controllers towards spawners.


There are two buttons in the panel "Fit To Terrain" and "Fit to World". Similar to the spawners these buttons will fit the biome controller to the terrain it is positioned over, or over the entire world of this scene.


Biome Spawners



This panel contains a list of spawners that make up this biome. You can activate and deactivate single spawners of the biome with the checkboxes for each entry.

The Area setting on top of the list of spawners is especially important: "Local" means the biome will only spawn within the current position / spawner range, while "World" means the biome will automatically be applied across all terrains in the scene (masks still apply for both modes).


With the "Create New Spawner" button you can quickly create a new spawner in the scene that will automatically be added to this biome as well. Great when extending an existing biome.

The "Set up in Stamper" button will copy the spawners from this list over to the "Autospawners" list in the Stamper in the scene - in this way you can stamp and automatically trigger the biome spawners afterwards. See the article page on the stamper for details.


Advanced


The Advanced Panel is home to multiple sub-panels, each of which control more advanced features of the biome controller.


Add Post Processing Volume: Allows you to add a post processing volume at the position / size of the biome controller. (Built-In Rendering Post Processing). This can be useful if you want to override post processing settings on certain areas of your world, matching the underlying biome.


Appearance: Holds settings related to Terrain Loading (Gaia Pro) and display of Scene View Gizmos.


Remove Assets from other Biomes: Allows you to create the biome areas from "Foreign" Biomes within the valid spawn area of this Biome. Imagine you start with spawning assets across the entire terrain, but later on you decide you want to spawn a desert biome in the center. With the feature in this panel you can clear out all "foreign" trees, grasses etc. from your desert zone so that only assets from your desert biome remain in this area.


Save and Load - Allows you to save the biome controller settings as a biome file - which you then can re-use in other projects / scenes.


Clear Spawns



Allows you to remove previously spawned object types, either only from this biome only, or from all biomes, and you can decide whether the deletion should be applied to a single terrain only or to all terrains in the scene.


Control Buttons


Last but not least there are two control buttons at the bottom of the spawner:



"Spawn Biome" will spawn the biome in either "Local" or "World" mode, depending on the "Area" setting in the list of spawners.

"Create Runtime" is a shortcut button to create the current Runtime Setup as configured in the Gaia Manager at that moment.