No
Yes 
Voxel Material
In a Voxel Graph (or in a C++ Voxel World Generator), you set the Voxel Material for every position in the world. A Voxel Material is composed of the following:
A and B are 2 materials indices, which are used in the UE material to select a color or a texture. The final material is Lerp(A, B, Alpha).
Voxel Actor is to choose the kind of Voxel Actors spawned at that position.
Grass vs Voxel Actors
I have 2 different foliage systems:
- Grass: no collision, using HISM
- Voxel Actors: spawned actors, triggered when floating
For example, in the following video, the grass is the cubes under the terrain, and the Voxel Actors are the cylinders:
Spawning rules
Grass and Voxel Actors are grouped in Grass Group and Voxel Actors Group. For each element of these groups, you can choose settings like max/min angle with the world up vector (not always global up vector, for a sphere world for instance).
You can then choose where to spawn these groups.
For grass, this is based on the material indices. You associate one or multiple material indices to a grass group, and that grass group will be spawned on voxels with those indices, with the density adjusted by the Alpha.
For Voxel Actors, this is based on the Voxel Actor property of a voxel material. Like the grass, you set one or multiple Voxel Actor ID to each group, and those group will be spawned on the voxels with these IDs.
For now there aren’t any specific nodes for biomes, but I definitively want to add some in the future. In the meantime, you can use the other nodes to create your own biomes.