Scenario Unreal Vfx

Unreal VFX (Niagara, Chaos destruction, VFX critique)

Expert level means an effect that tells the player the truth (where it hurts, when it is over), costs what its gameplay class allows across the whole world, and is proven by per-thread numbers on the target core count plus captures scored against a written rubric. Python cannot author Niagara emitters or modules (5.8 API): the agent works through templates with a User parameter contract, Material Instances, Effect Types and Dataflow recipes, and escalates the few graph edits as precise GUI requests. 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. Offline checks pass (python3 tests/code/unreal-vfx/run_all.py --offline); every in-editor snippet is not yet run in Unreal; job_00_vfx_probe.py answers the [verify] names.

Stance (the expert delta)

• Gameplay truth first. The boldest edge sits on the collision boundary (missile head, AoE rim) and reads the gameplay number (User.Radius = damage radius), never a hand-matched constant; lingering says "still dangerous" (Keyser #1 [00:09:44], [00:15:21]).
• Contrast is a screen budget. Near-white core, never pure white; saturation in the fringe; dark saturated halo; contrast highest at the head; a weak projectile gets a hotter core and dark wisps, not a brighter trail (Keyser #3 [00:08:13], [00:12:03]; #4 [00:19:55]). Unexpected white is usually stacked additive duplicates: count spawns before touching color, then back the additive core with an alpha-blended saturated layer (Shishido [00:17:42]-[00:18:14]).
• Timing is a story. Anticipation rides the character's cast animation (no window: put the interest in the falloff); build-up stops spawning exactly at the hit; the flash peaks on the hit frame ("intensity is not size"); consequences follow causes (flash, then debris and sparks, then smoke); dissipation is shorter than build-up and ends inside the gameplay window. A fast round head strobes: stretch it along velocity and bake motion blur into its texture (Keyser #5 [00:08:13]-[00:09:54], [00:14:34], [00:18:07]; #2 [00:03:31]; Shishido [00:30:00], [00:37:02]).
• Optimize the world, not the effect. An Effect Type on every system first: Lyra went from 227 to 103 active systems, RT 5.07 to 1.51 ms, same look (Kiraly [00:20:48]). The Effect Type is set per system, never per emitter; secondary emitters get Scalability Mode Self. Read GT, GT Concurrent and RT separately at the target core count [00:05:15], then pick a lever that saves that thread: distance culling stops ticking, not rendering, and the scalability manager pays for the check; cull proxies save the tick, not the RT [00:16:57], [00:18:02]; every GPU system pays an RT dispatch even unseen [00:05:47]. FX budgets only on non-critical types, with fx.Budget.AdjustedUsageDecayRate against oscillation [00:36:50]-[00:37:21].
• Spawn architecture by class and rate (Kiraly's table [00:45:57]): pool moderate one-shots (Manual Release means Release to Pool), a Data Channel listener for spam, stateless emitters with system state off for simple bursts (footsteps GT 1,387 to 271 us [00:39:24]); NDC and stateless are exclusive; small counts stay on CPU.
• Destruction cost is active bodies and contacts. Fix in order: rendering (Nanite on the GC, root proxy with the ISM renderer), body count and lifetime (clusters, Remove on Break with random timers and Cluster Crumbling, a per-platform removal multiplier, Tiny Geo), collision (one-way debris, one convex per cluster, boxes under 0.3 relative size), throttles last (Caillaud wPgd1J1Tf70 [00:03:47]-[00:16:18]; Xiao Yue zFiHDRREv7E [00:29:27]).
• Weapons break walls with strain, not fields. Apply External Strain plus Apply Breaking Linear Velocity scaled by projectile speed, no strain falloff; fields are "heavy and slow" (Van Allen [00:29:29]). Pick one damage model: Material Strength and Connectivity (tune tensile strength on the physical material) or per-level thresholds (tune the array); size-specific is a flag, not a model (Xiao Yue [00:19:54]-[00:20:27]). Heft comes from friction (combine Max) and low restitution; stone density is 2 g/cm3, 2000 is a unit error (Van Allen [00:26:11]).
• Recipes, not clicks. Templates with exposed parameters and Dataflow graphs with per-asset variables survive art changes and are what an agent reaches reliably (Caillaud t_jyTILDYo8 [00:02:46]).

Establish first

Workflow

1. Probe once per engine. job_00_vfx_probe.py (headless). GATE: probe.json answers the [verify] items.

2. Classify elements, group them into systems. classify_element per element, then system_plan: one Effect Type per system (its most critical element); the rest get Scalability Mode Self, or their own system when spammy or on GPU.

   System (examples)	Effect Type	Critical emitters	Secondary (Scalability Mode Self)
   Projectile, beam, tracer	NET_OneShotCritical	head	trail, wisps, embers
   Impact, hit, muzzle flash	NET_OneShotCritical	flash, damage ring	smoke, sparks (split if spammy or GPU)
   Debris or impact listener (NDC)	NET_OneShot, budget only with decay damping	none	all
   AoE, status, pickup	NET_PersistentCritical	rim	interior flavor
   Ambient dust, leaves, rain	NET_Ambient	none	all

   GATE: system_plan has no error.

3. Timing plan before building. Write the spawn schedule (wind-up from the cast animation, build-up ending at the hit, flash on the hit, debris and sparks, smoke, window end) and run spawn_schedule_verdict; strobe_risk(speed, head length) gives the stretch a fast head needs. GATE: no error; stretch in the template spec.

4. Template and contract. duplicate_template, user_parameters, contract_verdict; a missing control becomes one GUI request. Curves in that request pass fade_curve_verdict (opacity fades from mid-life, never shrink-only) and flipbook_playback_verdict (fast then slow). GATE: contract ok.

5. Look: materials and textures. Master material and instances from scenario-unreal-materials (erosion, gradient-map LUT, depth fade); reuse textures first (Trümpler [00:16:33]), generate glows, LUTs and noise in Python. Import masks with sRGB off, TEXTUREGROUP_Effects, big sources capped by Maximum Texture Size; baked flipbooks are premultiplied, so the material must divide RGB by A (premultiplied_check). Smoke and fire: baked flipbooks by default; Fluids are Beta. GATE: audit_vfx_textures, flipbook_check clean.

6. System properties and scalability. set_system_properties: effect_type, max_pool_size = the type's system cap, prime 0 for mid-play loads, warmup 0, current-frame data off for static effects; world-space trails need fixed bounds of speed x lifetime (fixed_bounds_check). Effect Types from EFFECT_TYPE_PRESETS (create_effect_type [verify] or GUI once). GATE: no NO_EFFECT_TYPE in audit_niagara; caps_verdict, budget_verdict clean.

7. Wire to gameplay. scenario-unreal-gameplay spawns with the pooling method, sets User parameters from gameplay data, spawns the wind-up from the cast animation, writes Data Channel payloads, applies strain on hit (strain_plan; collision plus strain for must-break objects). On hit, deactivate the trail and let its particles finish [added]. GATE: a PIE hit spawns from the pool (FX Outliner InUse / FreeInPool).

8. Destructible asset. Watertight, non-intersecting source (mesh_watertight_check); fixed seed; pattern by material (concrete noise and grout, wood shrink-fracture-stretch, glass slices or a crack material); two or three levels, anchored; Proximity graph with an area threshold; one damage model; one convex per cluster; interior material with a distance-to-surface bake (Caillaud t_jy [00:29:14]); Remove on Break ranges plus Cluster Crumbling; removal multiplier in the low-end device profile; disable settled debris that never wakes (Xiao Yue [00:28:45]). VFX on breaks needs Chaos data generation in Project Settings plus break notification on the component (enable_break_events, Xiao Yue [00:08:42]); switch only broken bones to a debris profile. Then harden_gc; piece count in a gym at 10, 50, 100 (Caillaud t_jy [00:35:12]). GATE: gc_recipe_verdict, gc_verdict, physmat_check clean.

9. Review loop. Textured review level, Manual exposure, the gameplay camera; live_capture_series.py or capture_ages with clean plates; score_captures.py (a blank frame voids the series); LOOK at the color, grayscale and squint sheets; repeat in PIE ("the viewport lies", Shishido [00:05:05]), over green and brown ground for the color-blind check, in a crowd grid and at sg.EffectsQuality 0 to 3. On white-out run duplicate_spawn_check on Debugger counts first. One change per pass. GATE: no rubric fail; judgment rows scored (references/critique.md).

10. Measure. Fixed worst fight at the target core count: stat unit, stat NiagaraOverview, Debug HUD, Insights with -statnamedevents (Niagara is invisible without it, Kiraly [00:10:52]); init_for_performance_baseline(); lever_check before each change; budget_oscillation when budgets are on. Destruction: frame series around the break, CVD, t.OverrideFPS 60 [verify]. GATE: niagara_overview_verdict, before_after, destruction_run_verdict within budget, visual parity.

11. Deliver the budget sheet to scenario-unreal-performance.