Why does foliage look flat in my scene?

Foliage instances default to Static mobility but may have Cast Static Shadow disabled or no precomputed lighting built. Without baked shadows, static foliage looks shadeless. Either build lighting (with Lightmass GI) or enable Distance Field shadows via Affect Distance Field Lighting + Generate Mesh Distance Fields.

What's the cheapest way to shadow foliage at distance?

Distance Field shadows. Build distance fields on the static meshes, enable Affect Distance Field Lighting on the foliage type, and turn on RayTracedDistanceFieldShadow on the directional light. This produces soft shadows out to ~1km with no Lightmass bake required.

Should I use HISM or Foliage Actor?

For static placed foliage, FoliageActor (via the Foliage tool) is convenient and supports painted distribution. For procedural or runtime-spawned instances, use UHierarchicalInstancedStaticMeshComponent directly — you control the spawn loop and can update lazily.

Fix: Unreal Foliage Instance Not Receiving Shadows

Quick answer: Enable Cast Static Shadow, Affect Distance Field Lighting, and ensure the static mesh has Generate Mesh Distance Fields on. For Lumen/raytraced setups, also check Cast Shadow As Two Sided for foliage with translucent leaves.

A painted forest of bushes and trees looks colorful but oddly flat — no shadows on the ground, no self-shadowing, leaves rendering as if facing a uniform light source. The directional light has Cast Shadow on. Other static meshes shadow correctly. Only the foliage looks wrong.

Foliage-Specific Shadow Pipelines

Foliage instances render through UHierarchicalInstancedStaticMeshComponent (HISM). Shadow paths supported:

Static — precomputed in Lightmass. Requires a lighting build.
Distance Field Shadows — runtime, soft shadows at distance.
Lumen / Ray Traced — runtime, accurate but expensive.
Cascaded Shadow Maps — runtime, near-camera, default for movable lights.

If none of these is enabled for your foliage type, it looks shadeless.

Fix 1: Enable Foliage Type Shadow Flags

Open the FoliageType asset (the SK_FoliageGrass, FT_Bush, etc.). In the details panel under Lighting:

Cast Static Shadow: true
Cast Dynamic Shadow: true
Affect Distance Field Lighting: true
Affect Dynamic Indirect Lighting: true

These propagate to every instance. If the foliage type doesn’t exist as a standalone asset (you painted with a static mesh directly), drag the static mesh into the foliage tool, choose “Promote to Foliage Type Asset”, and set the flags on the resulting asset.

Fix 2: Generate Distance Fields on the Mesh

For distance-field shadows to work, the source static mesh must have a distance field generated. Open the static mesh asset and under Build Settings:

Generate Mesh Distance Fields: true
Distance Field Resolution Scale: 2.0   // higher for trees

Click Apply Changes and wait for the rebuild. Check the asset has a distance field by clicking Show → Distance Field in the static mesh editor.

Fix 3: Project-Wide Distance Field Setting

Even with foliage flags correct, distance field shadows require:

// DefaultEngine.ini
[/Script/Engine.RendererSettings]
r.GenerateMeshDistanceFields=True
r.DistanceFieldShadowing=True

After editing, restart the editor. Without these, the engine doesn’t allocate distance field buffers and foliage shadows fall through.

Fix 4: Translucent Leaves Need Two-Sided

For tree leaves using a Masked or Translucent material, single-sided rendering means back-facing leaves don’t shadow at all — the leaf canopy looks like a wire frame from below. In the FoliageType:

Cast Shadow As Two Sided: true

And in the leaf material: set Two Sided to true. The cost is double pixel shader work for leaves, but the visual difference is dramatic.

Fix 5: Build Lighting or Switch to Lumen

For projects using Lumen Global Illumination, ensure Lumen is fully enabled:

r.Lumen.HardwareRayTracing=1
r.Lumen.ScreenProbeGather.RadianceCache=1

Lumen handles bounced lighting on foliage automatically without a bake. If you’re still on Lightmass, build lighting via Build → Build Lighting Only with Production quality. Foliage participates in the bake if its Cast Static Shadow is on.

Verifying

Toggle Show → Visualize → Shadow Frustums in the viewport. Foliage instances inside the cascade should produce shadow casters; if they don’t, the foliage type still has Cast Dynamic Shadow off. Save and re-test in PIE; the ground beneath foliage should show distinct shadow patterns.

“Foliage shadows need flags on the FoliageType, the source mesh, and the project. Miss any one and the canopy goes flat.”

A boilerplate FoliageType preset with Cast Static Shadow + Distance Fields enabled saves hours across new vegetation types.