Scenario Unreal World Building

Unreal world building (levels, open worlds, landscape, PCG)

Expert level here means a world sized by rule, placed by tier of importance, streamed and budgeted from the first map, and changed by script region by region, never by hand-selecting thousands of actors. The environment artist decides what stays manual, what is baked and what is generated at runtime, then proves every choice with a count, a trace or a screenshot. If a sibling skill named here is missing from your available skills, ask the user to install it (npx skills add scenario-labs/skills --skill <name>); unattended, proceed from tool schemas and flag the gap.

REQUIRED BACKGROUND: scenario-unreal-expert (channels, review loop, 5.8 traps). Toolkit: scripts/ue_world.py (sys.path[:0] = ["<skills>/scenario-unreal-world-building/scripts", "<skills>/scenario-unreal-expert/scripts"]; import ue_world as W) with ue_run, ue_review, ue_audit, ue_stat. Not yet run in Unreal: the offline layer passed tests/code/unreal-world-building/test_world_offline.py; [verify] names are resolved by W.probe(). A written plan names the engine call behind each W.* step (procedures P0 table).

Stance (the expert delta)

• Start from the integrated setup, then measure. File > New Level > Open World gives World Partition, OFPA, Data Layers, HLOD and outdoor lighting: "just use the template" (Sam Deiter, EEf07ggFWRw [00:20:40]). One runtime grid: more grids "can negatively impact performance" (World Partition doc). WP and OFPA from day one held 100,000 actors (Sam Dark, Subnautica 2, AalP65lrtpo [00:19:20]).
• Place by tier of importance. Hero assets and key areas by hand; shrubs to trees and rocks pre-baked; only grass-class detail generated at runtime on the GPU (CD Projekt RED and Epic, icIFFlOyob4 [00:04:23]-[00:07:05]). Collision and far visibility force persistent placement (Unreal Sensei, 5ju7wyvZGBI [00:54:16]). Bake what players do not perceive as varied; preview procedural output in the editor (Dark [00:07:56]). Decide what stays manual first (Matt Oztalay, TbNZ4GKaTow [00:32:26]).
• PCG is authored like materials. Template graphs with parameters, Graph Instances per use (Oztalay [00:12:18]); Is Partitioned is "pretty mandatory" [00:22:34]. Output inherits the PCG actor's Data Layer and HLOD Layer: assign them before generating (PCG doc). Grids: unbounded for parameters, 128 m for landscape reads, 32 m for scatter; every CPU to GPU transfer costs; layer weights do not exist on the GPU (icIFFlOyob4 [00:08:04] [00:23:16] [00:24:12]). Pop-in is generation latency, judged in Test builds [00:27:10] [00:27:44]. Bad data must be loud: Warn on Data Missing Attribute (Oztalay frame 00:10:47).
• A landscape is sized, not picked. Valid sizes (2017, 4033, never 2048), at most 1024 components, 2x2 sections, edit layers (Landscape doc). Z scale and actor Z come from the exported heights (Z = span / 512, actor at the midpoint), never a declared relief: 250 m on paper reached 314 m and clipped 123,356 pixels in our GREEN test [added]. The material contract, built by scenario-unreal-materials, is checked here: Opaque with Opacity Mask wired, one LB Alpha Blend base, a Layer Info per name (Landscape doc); triplanar only on the steep layer, anti-tiling on large layers, low specular (Sensei [00:11:12]-[00:15:36]).
• Nanite by default, construction still matters. "Enabled wherever possible" (Nanite doc), but porous kitbashes, hard-edge splits, seams and noisy vertex colors stop simplification: 250 MB vs 12 MB, same look (Epic, 6igUsOp8FdA [00:02:46]-[00:08:04]). Distance culling does not apply to Nanite (Nanite doc). Tessellation has no collision: per layer, center 0.5 on ground, 1 on vertical rock; dicing rate 2 [00:22:58] [00:29:53]. Foliage opaque and modeled (Quixel, aZr-mWAzoTg [00:01:46]).
• Streaming structure follows content. One HLOD layer per family: Instancing for foliage, Merged Mesh for buildings, Simplified when merged is still heavy (doc; Deiter [00:41:13]). Level Instance when content changes with gameplay, Packed Level Actor for static sets [00:30:59]. Runtime Data Layers only for gameplay state (doc). Teleport targets need a Streaming Source and, for runtime PCG, a generation source (doc; icIFFlOyob4 [00:36:44]).
• World-scale work is scripted, regional and validated. Scripts, never Outliner select-and-drag; whole-map jobs as builder commandlets region by region (Dark [00:20:23] [00:20:55]). Builders generate, then HLODs; generated actors stay out of changelists (Oztalay [00:26:23] [00:29:07]). Rules that documents only request become validators (Dark [00:23:04]).
• Kits are commitments. Footprint is the maximum extent, pivots frozen, standard door widths, core pieces first, hero last (Burgess and Purkeypile, QBAM27YbKZg [00:06:14] [00:07:51] [00:22:34]). Village paths join the nearest built path (Oztalay [00:20:01]); fences follow a spline grammar [00:18:51].

Establish first

Workflow

Each stage is an ue_run job or a live call; code in procedures (P-numbers).

1. Brief as a world spec (P1), like W.U1_EXAMPLE_SPEC; W.probe() once per install. GATE: W.check_world_spec(spec)["ok"], info findings answered.
2. Map (P2). W.new_open_world_map(path) from the template; old levels through W.convert_args(..., report_only=True) first. GATE: W.wp_facts_check(W.world_facts()) clean; PIE screenshot with wp.Runtime.ToggleDrawRuntimeHash2D.
3. Terrain (P3, P4). DCC heightmap or the blockout W.valley_heightmap; W.export_heightmap fits Z and actor Z to the real range. Creation is one Landscape mode step (Location Z = actor_z_cm, Scale Z = z_scale) unless an MCP tool does it [verify]. Edit layers Base, Sculpt Details, Paint, Splines, Patches. River (Water Body River or a Splines-layer spline) before heavy painting. Then the landscape builder. GATE: W.heightmap_clip_gate empty (0 clipped pixels) before import; W.landscape_facts() matches plan, scale and location; W.landscape_material_check clean; Layer Debug, cliff close-up, grass in sun, mannequin at 2, 10 and 100 m.
4. Organization (P5, P6). Editor Data Layers per family; HLOD layers from W.hlod_plan; Streaming Source components at teleport targets. GATE: W.data_layer_check, W.hlod_actor_check clean.
5. Village and kits (P7). W.kit_piece_check, W.door_width_check; houses as Level Instances or Packed Level Actors; clutter as tagged assemblies (W.tag_actors); paths by W.village_paths into landscape splines; fences by grammar strings. Version the map before breaking an instance. GATE: no kit errors; no z-fighting or obvious repetition from the paths.
6. Nanite (P8). W.nanite_construction_check(W.obj_construction_stats(obj)) on DCC exports; W.batch_nanite(paths, dry_run=True), read, run; W.tessellation_check with per-layer centers. GATE: no translucent Nanite mesh; Overdraw over the canopy; feet on displaced ground.
7. Baked PCG: forest and rocks (P9). Template graph (layer filter warning on missing data, slope density, Extents Modifier into Difference for paths, Distance thinning at banks, understory differenced against trees, Self Pruning, species table, collision on trunks only), checked by W.pcg_graph_lint; W.spawn_pcg_volume(..., hlod_layer=, data_layer=). Debug one volume (D) first. GATE: W.pcg_component_check clean; counts against W.expected_points; top-down and gameplay-height shots, nothing on paths or curated areas.
8. Runtime grass (P10). W.grass_rings() (dense to 128 m on 32 m cells, sparse to 256 m on 128 m cells, far edge recolored); mask from grass types without meshes through Generate Grass Maps; a placeholder in every asset array; editor viewport as generation source; landscape cache; pcg.FrameTime set. GATE: W.runtime_grass_check and W.find_gpu_transfers clean; W.generation_lead_check with latency measured on a Test build.
9. Builds (P11). for name, args in W.build_pipeline(map, graphs): ue_run.run_commandlet(uproject, name, args): landscape, PCG, HLOD. GATE: exit 0 each; HLOD actors per layer counted; W.changelist_check, then submit from the editor.
10. Review and handoff (P12 to P14). W.tour(...) with W.REVIEW_CONSOLE passes, ue_review.image_checks on every shot, then look; W.world_rules_check(W.world_census(), vocab); W.budget_sheet, W.lighting_handoff. GATE: critique rubric passes; nothing reported done without a capture.