PolyTerrain debugging

When Preview, bake, or Play misbehave, confirm Registry gates first, then use Outliner timing, Build To, and the ImGui diagnostics panel.

ImGui diagnostics

Typical columns: per-section last eval ms, ContentHash, pending dirty AABB, Build To layer, eval path (CPU / GPU when GPU Preview is used).

Outliner also shows last eval ms and ContentHash tooltips without ImGui.

Tool	Use
Outliner Build To	Truncate Preview to a Priority Layer while iterating
Rebuild Preview	Synchronous full (or Build To) refresh; invalidates in-flight GPU / async jobs
PreviewRebuildBudgetMs	Raise slightly if dense sections feel sticky; prefer Refine-only dirty regions
GpuPreviewEnabled	Faster Sculpt Preview only—never changes bake

Dirty rebuilds may run on AZ::Job and publish one frame later. Explicit RebuildPreview stays synchronous.

Topic	Guidance
Preview stroke	Target ≤ ~1.5 ms budget (`PreviewRebuildBudgetMs`); overflow goes async
Section span	Prefer ≤ ~2 km per section
Preview vertices	Cap via MPD Preview max complexity (default design target ~256 K)
Compiled / collision	Variant and Collision Transformer budgets (e.g. collision ~16 K tris)
Determinism	CPU evaluator is ContentHash authority; GPU Preview may differ slightly

Symptom	Likely cause	What to try
No Poly Terrain Mode menu	Registry off	Set `Enabled` and `EditorModeEnabled`; restart editor
Modifiers do nothing	Wrong layer / target	Layers must match MPD names; check `m_targetPartition` and Outliner order
Preview slow	Section too dense	Raise budget, Refine only dirty areas, Build To, or enable GPU Preview for eligible Sculpt
Bake skipped / stale	AP not running / hash	Confirm AssetProcessor; force non-incremental only if needed; check MPD pipeline
Seam cracks after Refine	Expected at displaced borders	Skirt Transformer; keep Shared border verts locked on Coarsen
Heightfield + mesh fight	Dual colliders	Sync Bridge exclusion; blend band; avoid dual physics owners on the same XY
VT / trails blank	`VtEnabled` false or no volume	Enable VT; assign `.vt`; cover with VT Volume + Box Shape
PIE missing terrain	Not baked / not in cell	Build Compiled Sections; confirm PrefabProcessor / WS cell membership
Boolean no hole	Non-watertight / failed CSG	Fix operand topology; check editor warnings; weights need re-paint after Boolean
Paint looks wrong after Boolean	Weights cleared	Move WeightPaint above Boolean; re-paint
PCG Write no-op at runtime	Gate / missing component	`PcgRuntimeExecutionEnabled`; pre-place PCG Write / Patch / MeshProjection components
Weight stamp ignored	Gate / non-authority	`RuntimeWeightRewriteEnabled`; clients cannot Submit when Multiplayer authority is server

Not a TerrainDataRequestBus provider—use GetUnifiedSurfacePointD or compiled mesh / SurfaceData.
Gem enable ≠ edit mode ≠ VT ≠ weight rewrite (separate keys).
Section entities are not net actors; only weight overlays replicate with the Multiplayer submodule.