Flora is the new detail rendering system by Procedural Worlds. Flora is currently a part of Gaia Pro and is in HDRP preview state. Flora allows you to display Terrain Details and Grass in HDRP, but also far exceeds the quality of the regular Terrain Detail System of Unity.

Please Note: Flora currently only works in the HD render pipeline. Running Flora in other rendering pipelines will not work. We will extend Flora soon to work in URP and Built-In rendering as well.

How to use / set up Flora manually

To use Flora on a terrain, simply add the "Flora Terrain Tile" component to the terrain. You can do this as with any other component, or you can do this via the Flora Window under Window > Procedural Worlds > Flora as well.

Source Camera and Terrain need only to be set if different from the current terrain and from the Main Camera. Flora then needs you to configure one Renderer each per Flora Detail Item you want to render. You can set those up manually by creating Flora Detail Item Configurations, or you can use the "Build Renderers From Terrain" Button to ingest the current unity terrain details from the terrain.

Once the Flora Detail items have been configured, the items will be rendered during runtime based on the selected terrain and camera. The position data will be taken either from Splatmap / Texturing Data, or from the existing Unity terrain detail system. You can choose this for each Detail Item and assign the source index.

e.g. if it is set to "Detail" and 0, it would render the Detail Item that is defined in the Detail Scriptable object at the position of all Unity Terrain Details at Index 0, in other words "The first terrain detail on this terrain".

Integration with Gaia Pro

When using Flora with Gaia Pro, the setup is even easier since Flora is directly integrated in the Gaia Spawner: When Setting up a Terrain Detail Resource inside a Spawner, there is a toggle to activate a Flora Detail Replacement for this item:

This allows you to insert an already configured  Flora Detail Item Configuration, or configure all settings for the Detail Item within the spawner directly (The settings offered in the Spawner and the Detail Item Configuration Object that is referenced in the spawner are 1:1 the same and the settings are "connected" with each other)

When spawning the Terrain Detail with Gaia as usual, the regular Unity terrain details will be placed which will then be automatically replaced with the Flora Detail during rendering. Gaia will take care of setting the Flora Terrain Tile component and configuring for you.

Please Note: Since Unity does not support Terrain Details itself in HDRP, you will only see white squares being rendered from the Terrain Detail System during Design Time. If those white squares annoy you, you can reduce the drawing distance for terrain details to 0  in the terrain settings. 
During Runtime, Flora will take over and display the actual terrain details. We are working towards a better solution for this that will allow you to at least estimate which terrain detail was spawned where during design time as well.

The Gaia Pro Grass spawners of the Gaia Pro Biomes are pre-configured to use Flora. This will have no impact on the other pipelines, but in HDRP Gaia will automatically replace the spawned Grass with Flora Details during runtime. If you prefer not to use Flora in HDRP, you can simply turn it off by unchecking the "Enable Flora System" Toggle in the Grass spawn rules.

Please Note: If you had a setup using the Gaia spawners before you installed a version that includes Flora, you would need to remove the Grass spawners from your setup and add the freshly installed new Grass spawner that holds the new Flora configuration data. (Before Flora the Grass spawners were simply disabled in HDRP)