Debugging and production patterns

Diagnose by layer

1. Topology — valid resolution, correct component/section layout, XY/Z scale.
2. Authoring stack — correct active Edit Layer, order, visibility, lock, alpha, procedural owner.
3. Paint contract — material name, Target Layer, Layer Info type, filled base, weight data.
4. Derived systems — splines, water, patches, grass/foliage/PCG, RVT, Nanite, collision, navigation.
5. Streaming — loaded region/proxy and dependent World Partition cells.
6. Runtime budget — shader, texture, virtual texture, geometry, shadow, instances, collision, I/O.

Useful visualizers and stats

• Landscape component/section/quads color overlays in Manage mode.
• View > Landscape Visualizers > Layer Debug for Target Layer channels.
• Lit > Visualizers > Layer Contribution for Edit Layer contribution.
• Player Collision and Visibility Collision view modes.
• Landscape.RenderNanite 0/1 for controlled representation comparison.
• stat virtualtexturing and stat virtualtexturememory for RVT.
• stat unit, stat gpu, GPU Visualizer, Unreal Insights.

Restore diagnostic overrides before final captures.

Common symptom table

Symptom	First checks
Tile seam/crack	source edge pixels, Flip Y, XY/Z scale, proxy freshness, Nanite skirt
Sculpt has no effect	wrong/locked Edit Layer, special procedural layer, alpha zero
Spline does not deform	missing Spline Edit Layer, raise/lower disabled, width/falloff
Black/default material	compile error, missing Layer Info/base fill, sampler/permutation
Wrong physical surface	dominant Target Layer and Physical Material assignment
Grass missing	Grass Output name/mask, Grass Type, Landscape-only boundary, culling
RVT contribution missing	bounds, asset type, writer list, pass type, sort priority
Nanite visual stale	dirty proxy; build/save/cook Nanite representation
Character floats/clips	collision mip or render displacement differs from collision
NavMesh breaks after sculpt	navigation not rebuilt or slope/step/agent settings no longer fit

Production test matrix

Axis	Minimum cases
Edit	sculpt/paint, undo, save/reload, layer reorder/hide, neighbor regions
Import	clean reimport, tiled seams, round-trip export, source checksum
Traversal	walk, fastest vehicle, steepest intended slope, world edge, teleport
Rendering	near/far, Nanite on/off, scalability tiers, target feature levels
Surface	each Target Layer, transitions, traces, footsteps/effects
Derived	splines, water, patches, vegetation, PCG, nav, HLOD/RVT
Build	PIE, standalone, cooked Development, shipping-equivalent target
Soak	repeated cross-world route and memory stabilization

Acceptance

• terrain supports intended mental map, sightlines, and traversal;
• no missing collision or navigation at streaming/edit boundaries;
• layer ownership is understandable and reversible;
• derived data can be rebuilt reproducibly;
• target frame, memory, disk, cook, and streaming budgets are met;
• no final conclusion relies on stale Nanite/RVT/nav/PCG data.