VFX pipeline

Path of Exile-level flash on a phone budget means smart layers, not raw particle counts. Every skill effect is a small set of cheap, well-timed layers that read at a glance and degrade gracefully.

◆Richness and review standard

Follow the per-skill semantic roles and visual self-tests. Richness means readable cue, motion, contact and end, plus footprint/status where relevant; it is not a minimum particle/emitter count. Every movement gem and buff also needs an intentional effect. Profile overdraw/material cost, CPU/GPU time and pools as well as particle counts. The caps below are Zoen planning values, not universal AAA standards. Review both cameras, Low/High, bright/dark terrain, crowd overlap and accessibility settings; never lose threat/party-utility readability. On movement cancel, stop cast-owned future cues/trails/bursts; effects on independent released entities follow their own lifetime. Full contract: cancel rules.

Small details that this page does not cover (impact placement, near-camera fade, overdraw rules, prewarming, what gives way first when a pool is full) are proposed in the AAA detail catalog.

◆Layers of one effect

◆Core techniques (Unity URP)

• Slash meshes: pre-modelled arc strips (Blender) with UVs along the swing. A Shader Graph uses a greyscale noise mask, an erosion threshold over time and a gradient map (palette ramp) for colour, so one texture serves every build colour.
• Particles: VFX Graph (GPU, compute) on native High/Ultra; the Particle System (Shuriken, CPU) on Low/Mid and in the Web build (WebGL2 has no compute shaders). Both definitions share timing and footprint.
• Flipbooks: 8×8 sheets from Blender (ART-VFX-040/041), premultiplied alpha, on billboards or ribbons.
• Trails: a Trail Renderer per weapon tip socket, enabled by animation events, width curve stretched by swing speed.
• Decals: URP Decal Projectors (decal renderer feature) with lifetime fade, capped at 64 live, recycled oldest-first. Telegraphs and player ground previews are not in this pool: a recycled telegraph would break the never-cull rule (proposed own renderer: VFX-04).
• Distortion: heat haze/shockwave as a renderer-feature pass only on High+, one at a time.
• Lights: at most 2 short-lived dynamic point lights per frame on High (Forward+; 0 on Low). Fake the rest with emissive sprites.

◆Palettes (from builds.json)

Each build has three palette colours (e.g. Warblade #e2b04a #fff1c1 #6b4a1f). Elements override the tint: fire #ff7a2a, cold #9fd3ff, lightning #b48cff, spirit fire #ffb347, sonic #5fd1a6, bleed #8a1e1e. Monster telegraphs are always red-orange #ff5a2a with a pattern fill (colour-blind safe), and player ground previews are jade #4fd1a0.

◆Budgets

The frame-wide totals and the own/party/others split are in Performance and 1,000 players.

◆Data format

Each skill gets apps/client-unity/Assets/Zoen/Fx/Defs/<skillId>.json (read by the effect player; VFX Graph and Particle System assets referenced by id):

{ "skill": "warblade.horizon_cleave",
  "events": [
    { "at": "windup:0.00", "fx": "glint_blade", "socket": "weapon_r", "tier": "all" },
    { "at": "contact",     "fx": "slash_arc_160", "palette": "warblade", "scale": 3.2, "tier": "all" },
    { "at": "hit",         "fx": "impact_by_material", "tier": "all" },
    { "at": "contact",     "fx": "ground_dust_sheet", "tier": "mid+" } ] }

contact and hit are server events. windup:t is relative to the predicted cast start.

◆Pipeline per skill (tasks)

1. Read the presentation.vfx brief and palette, then write the def JSON with greybox shapes (timing first).
2. Build or reuse textures (flipbooks/slash meshes). New textures come from Blender scripts and are logged in the art library.
3. Tune in the VFX Lab scene (Combat Lab + slow-motion scrubber + Low/High toggle).
4. Tests: event alignment vs server contact (±16.7 ms), budget counters per tier, pool return (no leaks after 1,000 casts), telegraphs visible on Low.
5. Evidence: 10 s clip at Low and High side by side, sent to the owner for review on signature skills.

◆Quality tiers and the Ultra feel stack

Tiers are data (feel-quality.json), read by the Feel Lab today and by the client settings menu later. Every tier keeps the same hit shapes, timings, reactions and telegraphs. Tiers only add presentation layers.

• Screen vibrate means two things. The camera gets a 0.22 s high-frequency rattle on massive hits (Ultra), on top of the trauma shake. The device gets haptics on every tier: Vibration API patterns on phones and dual-rumble on gamepads, scaled by impact. Haptics fire only after the player has interacted, at most once per 60 ms.
• Settings: Graphics quality, Screen shake 0–100%, Haptics 0–100% and Reduce flashing. Reduce flashing removes impact frames and colour-split pulses and clamps bloom.
• No white-outs. An impact frame is at most 60 ms, a 420 px burst around the hit and never full screen. The glow layer takes only 20% of a struck target's hit flash, so flashes read as rim light.
• Implementation notes (Feel Lab, components/feel/engine.ts):
  • Debris is one thin-instanced mesh driven by typed arrays (one draw call, no per-frame allocation).
  • Decals are a fixed pool, recycled oldest first.
  • The shockwave is one full-screen post pass that exists only on Ultra.
  • One-shot particle bursts never dispose the shared sprite texture.
• Measured (Playwright, desktop, Sunbreaker playing): High and Ultra both hold frame p95 ≈ 16.7 ms (logs/evidence/T048/frame-times.json). Clip: feel-ultra.mp4 on the Showcase page.

◆Readability rules

• Never hide a telegraph. Player effects render under monster telegraphs.
• Other players' effects default to Reduced (50% particles, no lights, no distortion). Own effects stay full.
• Bloom is capped. Flash-reduction mode clamps peak brightness and removes white-outs.
• The effect footprint must match the hit shape (a 3 m cone looks 3 m). The test overlays the shape on the capture.