Scenario Unreal Animation

Unreal animation (technical animator)

Expert level means contact that holds on every clip the game plays, locomotion authored against the movement model that changes category on the input frame, animation that costs a measured number of milliseconds on the target, and clean data at the source. The agent works through data and templates: it scripts assets, IK Rigs, retargeters, databases and settings, duplicates Epic's AnimBPs instead of drawing graphs, measures contact numerically, then looks at frames. 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): Unreal is not installed. The offline layer of scripts/ue_anim.py passed 30 tests (python3 tests/code/unreal-animation/run_all.py --offline). Every in-editor snippet is not yet run in Unreal; [verify] names are answered by job_00_anim_probe.py. Import: sys.path[:0] = ["<skills>/scenario-unreal-animation/scripts", "<skills>/scenario-unreal-expert/scripts"]; import ue_anim as A.

Stance (the expert delta)

• Cheapest transfer first, then retarget order decides contact. Same skeleton, compatible skeletons, Copy Pose From Mesh or Leader Pose beat an IK Retargeter (Greg Richardson, -8CQNaODNNA [00:02:40]-[00:06:04]). When retargeting: a new named retarget pose (never Default) with auto align, snap to ground, slight knee and elbow bend; Scale Source once at the top, judged by the IK goals; Blend to Source on leg IK or feet sink; auto-exported retargeters have IK off (Richardson [00:08:13], [00:16:29], [00:21:26], [00:29:14]). Pin the IK helper bones gameplay reads (ik_foot_l/r, ik_hand_gun); one-off fixes go in an Additive Pose op, not the base pose (Richardson [00:33:16]; 5.8 retargeting doc).
• Movement model first, then animate against it. Tune capsule speeds, acceleration and braking with rough animation until it plays well, export the capsule trajectory, animate the root frame-exact with the chest (not the hips) within tolerance and 5-frame stops where the body overshoots. This separates animation bugs from system bugs (GASP team, Tony, mhVp_cC9MLc [00:24:25]-[00:28:43]; Dustin DeVoe, FLDXtAV7qsw [00:06:27]-[00:08:40]).
• Motion matching is data under designer control. Split databases by movement state, pick them with a Chooser on cached enums, interrupt only when a core state changed this frame, keep root motion enabled on every locomotion clip even when the capsule drives (GASP team [00:29:43]-[00:40:54], [01:30:00]). Weights encode a preference between imperfect candidates with low coverage (Sam [00:49:01]); they never fix a speed or coverage mismatch, and late tuning uses notify-state tags, not schema weights (Jose, tNw9lD2PW3U [00:18:28]; motion matching doc).
• Small sets ship with procedural nodes. 13 clips give a non-strafing base, 26 with strafing, 60 to 80 with states, both feet for every start, stop and refacing start (DeVoe [00:11:14]-[00:14:44]); "a misnomer that you need all coverage" (GASP [01:21:06]). Sparse data needs Steering before Offset Root Bone, foot placement and mesh-space additives, not a state machine (DeVoe [00:28:19]-[00:31:40]).
• Keep the AnimBP off the game thread, and budget root motion. Thread-safe update, Property Access, fast path on every node (Matthew Lake, N_suMyUuork [00:12:44]-[00:16:53]). Root Motion from Everything AND from Montages Only both update the AnimGraph on the game thread (root motion doc; Lake [00:13:18]). Montages Only is chosen because capsule-driven locomotion networks well, not to save threads: budget its cost; a character with no root-motion montage can use No Root Motion Extraction [inference from the doc wording, verify in Insights].
• Clean at the source, throttle what is unseen. Stripping twist, face and deformation tracks and Maya helper curves cut storage 71% and memory 90% on one clip; import defaults set project-wide, not per asset (Lake [00:05:15]-[00:07:21]). Only Tick Pose When Rendered as the project default, budget allocator or URO (never both), one LOD Settings asset with hysteresis (Lake [00:21:13]; AnimBP doc).
• Control Rig: Construction caches, Forwards Solve per frame. Profile before converting to C++ (60 µs graph vs 10 to 16 µs rig unit); FBIK adjusts a pose, it does not create one; exclude bones instead of locking them; a Backwards Solve makes a rig bakeable (Stéphane Biava, XYMad1EutcA [00:10:08]; LEGO Fortnite tech animator, kO6pz8ADgcU [00:12:04]).
• Never ship the cinematic MetaHuman. About 800 MB cooked vs about 60 MB Optimized High; audition LODs at the game camera from LOD 2 on PS5-class; Mac renders cards only (DeVoe, tTgMafRAM7A [00:15:16], [00:23:34]).

Establish first

Workflow

1. Probe once per engine. job_00_anim_probe.py headless. GATE: probe.json lists IK Rig, retargeter, Pose Search, AnimPose, Interchange, MetaHuman names and whether 5.8 BlueprintGraphEditor exists.
2. Receive and audit the character. A.import_character / A.import_animations (explicit options on either importer), then A.import_audit(A.skeletal_mesh_facts(mesh)): one root, unused bones (5.8 Bone Count Reduction), influences over 8, units. Set project-wide import defaults once: A.apply_ini_plan(cfg, A.import_defaults_plan()) for the legacy importer, the project pipeline in the Interchange Import Content stack. GATE: no error; mesh looked at in a neutral lit preview.
3. Choose the transfer. A.transfer_method(source, target). GATE: method and reason written down.
4. IK Rigs. A.create_ik_rig (5.8 template splits Leg at the ankle and adds Foot chains), A.biped_chain_plan for custom names. GATE: A.chain_map_check clean.
5. Retargeter, built once, then templated. A.create_retargeter; op settings once in the GUI, saved as RTG_Template; Pin Bones from A.ik_bone_pin_plan(bones, A.mannequin_bone_map(bones, parents)). GATE: A.op_stack_check(ops, proportions_differ=True, target_ik_bones=..., runtime=..., profile_ops_us=...) clean; A.retarget_log_check on the Retarget Output Log clean; LOD thresholds and Profile Ops for any runtime retargeter.
6. Batch retarget and clean. A.batch_retarget(..., retain_additive=True); mocap through its own retargeter (Filter Bones, Generate From Target Pelvis); A.anim_content_audit, A.ensure_root_motion, A.strip_curves. GATE: A.compare_contact on walk, run, turn, crouch, jump, a contact clip and a mocap clip; A.root_motion_check; contact frames looked at side and front.
7. Movement model and authored clips. Tune the movement component per gait and direction; export the capsule trajectory (5.6+ Rewind Debugger > Trajectories export, else Take Recorder) to scenario-maya-animation or scenario-blender-animation. GATE: A.capsule_match (root on the path, chest within tolerance, root stops with the capsule) and A.speed_parity on returned clips.
8. Locomotion architecture. A.decide_locomotion(...). Motion matching: migrate GASP, A.motion_matching_coverage (foot pairs, capture shapes), A.database_plan, duplicate schemas and databases, then remap every mannequin bone name: A.schema_bone_check(A.schema_facts(s)["bones"], bones, bone_map), Pose History bones in the GUI; tags, notify filtering, repetition guards. Procedural nodes: A.procedural_order_check, A.offset_root_bone_modes. GATE: zero "no database" warnings cycling every state in PIE; Rewind Debugger read on each transition frame; starts, stops, pivots at 0.25 timescale from a still camera.
9. Root motion and montages. A.root_motion_mode_check(mode, multiplayer, montage_root_motion); A.montage_blend_out_check; traversal tails through a JustTraversed database. GATE: no root velocity in the blend-out window; show collision capsule stays with the mesh; game thread measured.
10. Foot IK. GASP 5.4 leg IK only locks feet to the IK foot bones, no ground adaptation [verify current GASP]; slopes and stairs need Foot Placement or a Control Rig with FBIK (A.fbik_foot_defaults(mannequin_like=False) re-derives the knee axis). Sequencer shots: CR_GroundAlignment on the mannequin, then retarget. GATE: stairs and 30 degree slope captures, foot gap per frame, no pop, no jitter.
11. Performance pass. A.anim_ini_plan, A.animbp_settings, A.compile_and_scan, A.allocator_config_check, A.lod_settings_check. GATE: stat anim, stat unit, Insights before and after on the same path.
12. Deliver per Handoffs, with what was not verified.