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Epic’s PCG samples: assemblies, flat ground and biomes
Know first: Plant a forest by rules in PCG
This breakdown takes apart the free examples Epic made for PCG, the Procedural Content Generation framework of Unreal Engine: the Electric Dreams Environment sample and the PCG Biome Core and Biome Sample plugins. Unlike a talk, these can be opened in the engine, graph by graph, changed and copied. The sources are Epic’s documentation pages for both. What makes them good examples: they show how hand-built pieces and rules work together. They also solve small, real problems, such as how to keep a stone slab from floating over a bump.
The whole picture
| Part | The problem | The answer |
|---|---|---|
| Assemblies | Rules alone look plain; hand-built pieces don’t scale | Build a piece by hand once, turn it into points, and let rules copy and vary it |
| Point hierarchy | A trunk and its branches must move together | Points remember their parents, like objects in a level |
| Flat enough? | Large flat assets float over bumps | Probe the ground around each point and drop the bumpy spots |
| Biome Core | Many projects build a similar biome tool from scratch | A fixed pipeline of graphs, driven by data, ready to copy |
Electric Dreams was shown at GDC 2023 as a first look at new features of Unreal Engine 5.2. Its full level is a world of 4 × 4 km with “both hand-crafted and procedural areas”. The sample also has smaller breakdown levels: a large cliff built from assemblies, a ditch wall along a spline, a forest with parameters, and an assembly stretched along a path.