How does PCG turn points into rendered meshes?

A Static Mesh Spawner node receives a point set and a mesh selection (single mesh or weighted list). It creates a Hierarchical Instanced Static Mesh component on the PCG actor with one instance per point. Without this node connected to the graph output, points exist but render nothing.

Why are no points generated inside my volume?

Source nodes like Surface Sampler or Volume Sampler need a bounds input. If the volume actor’s bounds are zero (e.g., a default-scaled BP), no points generate. Resize the PCG volume to enclose your terrain region and force a regenerate.

How do I force PCG to regenerate?

Select the PCG actor and click Generate in the Details panel. Or move/resize the volume — auto-regenerate fires. For programmatic refresh from script, call PCGComponent->Generate().

Fix: Unreal PCG Graph Output Not Spawning Instances

Quick answer: Connect the graph’s point output to a Static Mesh Spawner node with a mesh selection, place the volume to enclose your sampler bounds, and click Generate or move the volume to trigger regen.

A PCG graph samples points over a landscape to scatter rocks. The PCG Inspector shows 3000 points generated, but the viewport is empty — no rocks render. The graph runs; the data flows; no geometry appears.

Points vs Geometry in PCG

PCG data flows as point sets: positions, rotations, scales, plus optional attributes. Points are abstract data, not visible geometry. To render them, you connect to a Static Mesh Spawner or Spline Mesh Spawner node, which creates ISM (Instanced Static Mesh) components on the PCG actor.

If your graph ends with the point set going to the Output node and no Spawner anywhere in the chain, the points are computed but never rendered.

The Fix: Add a Static Mesh Spawner

In the PCG graph editor:

Right-click → Add Node → Static Mesh Spawner.
Connect the input from your last point-processing node (e.g., Transform Points).
Connect the Spawner’s output to the graph’s Output node.
In the Spawner’s Details: set Mesh to a valid Static Mesh, or use Mesh Selector Weighted for variety.

Save the graph, return to the level, and force regenerate.

Verify Volume Bounds

If the sampler still produces zero points, the volume actor’s bounds are wrong:

Select the PCG actor.
Resize its volume to enclose the area you want to populate.
In Details, click Generate.

For Surface Sampler specifically, the surface to sample must intersect the volume. A volume floating in space with no landscape inside produces no points.

Force a Regenerate

PCG doesn’t auto-update on every edit. Triggers include:

Clicking Generate in the PCG actor’s Details.
Moving or resizing the volume.
Saving the graph (sometimes; depends on project settings).
Calling PCGComponent->Generate() from script.

Until a trigger fires, the cached output is what you see. Always Generate after editing the graph.

Diagnosing

Enable Inspect on a node (right-click → Inspect). The PCG Inspector panel shows point counts and attribute values flowing through that connection. If the sampler shows non-zero but the Spawner shows zero, an intermediate filter is removing all points. If the Spawner shows non-zero but no meshes appear, the Mesh field is unset or null.

Verifying

Generate the graph. Rocks should appear scattered across the landscape. Toggle the PCG actor active/inactive to confirm they’re tied to its ISM. Move the volume; on next generate, rocks should re-distribute to the new area.

“PCG points are data. Static Mesh Spawner turns them into rendered instances. Without the spawner, you’ve generated a math abstraction, not a forest.”

Inspect every connection while authoring a new graph — the moment a downstream node shows zero is the moment something went wrong.