Painting terrain details (e.g. grass billboards) programmatically?

[churlishcanadian]

Is it possible to paint details such as billboarded grass textures programmatically? (The kind that appear vertical and wave according to wind settings, that is.)

What I know so far (or think I do):

• Terrain.TerrainData.terrainLayers holds the “flat” textures (dirt/rock/grass) that can be painted onto the terrain
• Terrain.TerrainData.detailPrototypes holds the billboard-able grass/vegetation textures that can be painted to appear vertical / waving in the wind
• Terrain.TerrainData.treePrototypes holds the 3D tree models imported for placement
• Terrain.TerrainData.treeInstances holds (I would guess) actual placements of trees on the terrain

What I don’t know:

• MY MAIN GOAL: “Paint” billboarded grass details at specific positions on the terrain programmatically
• Alphamaps (and splatmaps??) seem to figure into this somehow, but I don’t know how
• The example found here “blend[s] the two terrain textures according to the steepness of the slope at each point”, but that’s not exactly what I’m trying to do.
• I also found this fairly ancient (2014) blog post, but I don’t see any reference to adding billboarded brass details in it either.

Hopefully this makes sense to someone willing to point me in the right direction.

[bixarrio]

I seem to have missed this.

Painting terrain details in code is much the same as the trees. You’ll add detailPrototypes with the grass textures (or meshes) and then add a detail map (float values between 0 and 1) representing the density of the details at a specific location in the terrain, 0 being nothing and 1 being many. The terrainData has a detailWidth and detailHeight that tells you the dimensions of this detail map