scenario-unreal-pipeline-automation

Unreal pipeline automation (pipeline and tools TD)

Expert pipeline work in Unreal is policy as data plus proof: the import policy is a versioned pipeline asset, names come from a plan, every rule that matters is a validator that also guards human edits, and a build counts once it cooked with fatal validation and booted. Bulk work runs headless; anything visual goes to a screenshot someone actually looks at. 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).

Status (2026-09-24): every Unreal call here is not yet run in Unreal; the pure layer of `scripts/ue_pipeline.py` and both jobs ran offline (unit tests, plus control flow against a fake unreal). First action once 5.8 is installed: tests/code/unreal-pipeline-automation/in_engine/run_in_unreal.py.

Stance (the expert delta)

• Import policy is an asset you pass, never dialog memory, and it sticks to the asset. Scripted

imports use the pipeline's defaults, not what the dialog last remembered (Interchange PM, Oq6KbrqkGnw [00:39:28]; Jamie Dale, 0guOMTiwmhk [01:26:38]): duplicate the generic assets pipeline into the project, set every option, pass it in override_pipelines. Stack order is execution order: a tweak pipeline above the default one sees no factory nodes [00:20:22]. Filter at factory-node level, following Factory Dependencies, so orphan materials are never created [00:31:33]; a Graph Inspector left in the stack pops up mid-batch [00:40:00]. An asset keeps its stack and reimport reuses it (Interchange doc), so a policy change reaches existing assets only through a reimport that passes the new preset (plan_imports(..., policy=)).

• Names come from the plan, not the importer. Interchange ignores

AssetImportTask.destination_name (5.8 API reference). Stage each file under its target name and rename only as a fallback: a rename leaves a redirector (naming doc), and the Zen loader ignores core redirects. Renaming onto an existing asset fails, which is how re-runs leave duplicates: reimport instead (I03). No drag and drop: other tools depend on paths (Bardoux, MjjkWH0eT3U [00:09:14]).

• Nanite by eligibility, not triangle count. Opaque or masked static meshes on a Nanite target

get Nanite, low-poly included: non-Nanite geometry is "much more expensive to render into VSMs" (VSM doc). Off for translucent materials (Nanite draws the default material), morph targets and non-Nanite targets; "not everything can be Nanite" (Oztalay, S2olUc9zcB8 [00:34:33]). Fallback settings on every Nanite mesh (DxBKmQ-0kfw [00:37:15]); simple collision still required.

• Validation is code at the point of creation, and red must mean new. About 30 to 40 percent of

bugs trace back to something an asset validator could catch (Fray, KuIWCzujtag [00:35:40]). Keep CanValidateAsset cheap [00:31:47] and watch each validator's cost in 5.8's per-validator cook stats (DataValidation.ReportCookValidationStats); allow-list legacy errors [00:38:07]; see each check fail on a fixture first [01:46:04]. Python validators register every session, -run=DataValidation runs C++ rules only, and cook validation without -ValidationErrorsAreFatal turns errors into warnings.

• Headless for bulk, the open editor for what it holds, and no trust in exit codes. The

commandlet loads no level (Python doc) and the registry may still be scanning: wait_for_completion() before queries (5.8 batch example). A Python failure only logs an error unless -ScriptErrorsAreFatal (5.5): the verdict is the job's own result line (P.job_verdict). The editor keeps a write lock on loaded assets (Jamie Dale [01:17:18]): run inside it through MCP or Python remote execution. set_editor_property behaves like the Details panel; plain attribute writes rebuild nothing [00:21:25]. Under Perforce, 5.8's PythonScript commandlet enables source control first; check out what you will save and stop if checkout fails (Bardoux [00:55:27]). Imports are not undoable: snapshot first.

• List, confirm, act, one pass per mesh. Print the resolved targets, then run (Sam Deiter,

k0tgmrBuIJc [00:52:23]). Set Nanite, LODs and collision in one pass and save once per chunk. A LOD group may not build LODs by itself [verify]: count after setting it, build the chain explicitly if short, check screen sizes decrease (L02). One bad file never stops the batch.

• A build is a reproducible command line, proven by booting. Generate the BuildCookRun line once

from a Project Launcher profile and diff yours against it (UAT doc; P.buildcookrun_diff). Cook does not stage, -skipcook is not omitting -cook (Josh Adams, uxdEt9XXKb8 [00:19:14], [00:20:20]); Xcode assembles the .app whether or not anyone edits in Xcode [00:03:33] (that content-only projects need full Xcode is an inference to verify). Same command locally and on CI (Hamilton, 3ftOkc-cA7U [00:25:15]); then boot it (Gauntlet UE.BootTest) and stay to watch (Ari, 102O0FOEzNY [00:39:07]). Performance numbers are trends, not gates (Fray [01:29:38]).

Establish first

Workflow

1. Preflight. ue_env.preflight() (chip, Xcode window), P.project_path_problems, plugins

(Python Editor Script, Editor Scripting Utilities, Interchange, Data Validation, PythonAutomationTest), editor holding the project, p4 opened. GATE: no error line; channel chosen (P0).

1. Plan and stage, offline. P.scan_sources, P.read_dcc_manifest,

P.plan_imports(..., previous=manifest, policy="PL_Props@3"), P.stage_plan. GATE: items plus rejections equal sources; D01 to D07 read; sources byte-identical (P1).

1. Import policy. Job describe, then preset with a route: post_import (default: materials

off, instances built after import with an explicit parameter map) or interchange_mi (Material Import = Import as Material Instance, Parent Material = master; fills only parameters Interchange knows by name). Vertex Color Import Option Ignore unless the master reads vertex color; Generate Lightmap UVs off for Lumen. GATE: failed empty; P.pipeline_stack_problems(stack) clean (P2).

1. Trial. make_fixtures.py plus 5 to 10 real files. GATE: each broken fixture shows its issue

id; seconds per file known.

1. Import. Headless: job import through ue_run.run_python; editor open: P.run_import_plan

through MCP or ue_remote.PythonRemote; engine calls in P3b. Chunks of 25, unreal.collect_garbage(). GATE: every file accounted for, P.job_verdict exit 0 (P3, P4).

1. Validate. Report carries our issues, engine_validate and ue_audit; -run=DataValidation

for C++ rules; P.new_issues(records, allow) decides CI. GATE: zero new errors; validator cost known (P5).

1. Look. ue_contact_sheet_job.py (latent screenshot loop shown raw in P7), then

ue_review.review_images; open the sheet; collision view on a sample. GATE: no blank frame; a note per flagged asset.

1. Redirectors and check-in. redirectors_found (from the registry) above 0:

P.resave_command(uproject, autocheckout=...), editor closed. GATE: zero (P8).

1. Tests. Python tests (test_*.py) via P.automation_command, read with

P.parse_automation_report; tiers push, build, weekend (Fray [01:31:46]). GATE: all pass; each new test seen failing once (P6).

1. Cook, package, boot. Iterate content with P.cook_command (cook only) or

package_command(..., incremental=True) (-cookincremental, Beta, Zen); release: P.zen_ci_patch, P.package_command, P.buildcookrun_problems, P.buildcookrun_diff against the launcher line, ue_run.run_uat, P.parse_uat_log, P.gauntlet_command. GATE: exit 0, .app archived, BootTest passes (P9).

Numbers

Quality gates

Measurable: items plus rejections equal sources; summary["ok"]; zero new errors; validators registered and engine_validation.ok; ueaudit `pass`; `redirectorsfound empty; DataValidation clean; automation failed 0; cook with -ValidationErrorsAreFatal; P.job_verdict exit 0 per job; launcher diff reviewed; UAT exit 0; .app exists; BootTest passes. Rubric: [references/critique.md`](references/critique.md).

Visual: the contact sheet (scale next to a mannequin, pivot, normal green channel, texture slot, LOD pops with r.ForceLOD), collision view on a sample, Nanite visualization, lookdev under scenario-unreal-lighting-rendering's rig.

Common mistakes

Handoffs

Receives: from scenario-maya-pipeline-scripting, FBX per asset in cm, UCX_<mesh>_NN, <file>.settings.json, summary.json with sha1; from scenario-zbrush-retopology-export, OBJ in cm, feet at 0, maps; from Blender, FBX or glTF with DirectX normals or an opengl flag (scenario-blender-uv-baking); from scenario-unreal-materials, master paths, parameter map, whether the master reads vertex color; from scenario-unreal-lighting-rendering, a lookdev level.

Delivers: assets plus report.json, report.csv, manifest.json (sha1 and policy per source) and the not-verified list. Skeletal items to scenario-unreal-animation, M04 gaps to scenario-unreal-materials, props to scenario-unreal-world-building. Issues go back by id (D01, D02, S01 to scenario-maya-pipeline-scripting; T01 to the texturer). Builds go to QA and scenario-unreal-performance as archive path, UAT verdict, BootTest result and changelist.

UE 5.8 notes

• Interchange handles FBX (production since 5.5); 5.8 renamed dialog options, added uFBX

(Experimental), made USD asset import production ready. InterchangeManager.import_asset and reimport_asset return the objects or None (5.8 API).

• AssetImportTask.result is deprecated (get_objects()); validator overrides are

k2_can_validate_asset and k2_validate_loaded_asset; create_asset gained overwrite_existing.

• Batch processor: BatchProcessLibrary.run_batch; guard scripts imported from init_unreal.py

with __main__ (fork bomb).

• Zen cooked output store on by default: LimitProcessLifetime=false for CI; cooking inside the

editor is removed in 5.9.

• Remote Control blocks remote UFUNCTION calls by default: trigger imports through Python remote

execution or MCP.

• Action utilities with empty SupportedClasses fail validation. The Interchange page still shows

"Experimental" FBX cvars: read them on install (job flags).

• Python 3.11.8.

References

• `references/procedures.md`: P0 to P14 plus P3b (the raw engine calls),

each with test path and status.

• `references/expert-notes.md`: judgment by source, disagreements and

deciding conditions.

• references/critique.md: rubric for a run, a validator, a test and a build.
• `references/gui-paths.md`: menus for the same procedures.
• `references/sources.md`: sources, credentials, timestamps, revision

history.

• scripts/ue_pipeline.py, `scripts/ue_pipeline_job.py`,

`scripts/ue_contact_sheet_job.py`.