It is possible to read and write mesh partitions from a PCG graph. This can be powerful and opens up many possibilities. For example:
Creating a custom erosion effect.
Applying material effects automatically.
Scattering assets using mesh partition weight channels.
Here is an example of a PCG graph used to apply an erosion effect on the mesh partition.
You can set the mesh partition Query and Write nodes to read the mesh up to a specific priority layer and then write back results to another specific layer.
Best practice is to connect the same priority layer and sub-priority into both the mesh partition Query node and Write node. Avoid setting up the Query as inclusive by default, in order to avoid feedback loops with each graph generation.
PCG Mesh Partition nodes
Query
The mesh partition Query node loads the mesh partition surface geometry within the PCG volume. You can then sample it, or convert it to points using the ToPoint node. It can also get weight channels.
ToPoint
The ToPoint node converts mesh partition geometry surface from the mesh partition Query node into PCG points.
Write
The mesh partition Write node writes back modifications done to mesh partition points. The number of points has to match the value provided by the mesh partition Query node. The original positions of the points, before any PCG operations, have to be stored in a FVector attribute (for example, SourcePositions). Alternatively, you can keep the original position unaltered in the Position attribute and modify the Destination Positions attribute instead.
Patch Instance Spawner
The mesh partition Patch Instance Spawner spawns patch instance modifiers from its input PCG points.
Mesh Projection Instance Spawner
The mesh partition Mesh Projection Instance Spawner spawns mesh projection instance modifiers from its input PCG points.
