RFC-019 + RFC-020: Visual identity + post-FX bus + multi-source layer compositing (paired)

[chipi]

Summary

Paired RFCs that bring the seven-RFC audio arc's depth to the visual side. RFC-019 introduces a visual identity switch and a post-FX bus (the visual analogue of RFC-012); RFC-020 introduces multi-source layer compositing with the feedback layer as the keystone primitive. Ships paired — post-FX operates over composited output, the identity switch broadcasts coherent layer defaults.

The primitives are grounded in three reference aesthetics surfaced by a parallel aesthetic research pass: Ryoji Ikeda (stroboscopic minimalism), Bill Viola (slow cinematic meditation), Memo Akten (accumulated trails + flow). The single most important architectural insight: a parameterised feedback buffer serves all three aesthetics from one primitive (fade = 0.0 / 0.96-0.98 / 0.99+ for Ikeda / Akten / Viola respectively).

RFCs

• RFC-019 — Visual identity + post-process bus
• RFC-020 — Multi-source layer compositing

Scope — RFC-019

• Visual identity switch: `cinematic` (Akten) / `minimalist` (Ikeda) / `meditative` (Viola) / `painterly` / `technical`
• Post-FX chain primitive — ordered effects pipeline, every param polymorphic per RFC-014
• Effect catalogue: bloom (threshold range matters: Viola high / Akten low), glow, chromatic aberration (centre / velocity-source), grain (per-frame regen default), vignette, color_grade (LUT), two_tone_grade (Viola submerged palette), threshold_binarize (Ikeda), nearest_scale (Ikeda pixel-grid integrity), blur_radial, scanline, displacement
• LUT bank in `visual/luts//metadata.yaml` with license gate (CC0 / CC-BY / open) — mirrors RFC-012's vocal sample bank discipline
• Always-on subtle drift — Cloud Filter analogue, low-depth low-frequency displacement
• Camera as envelope-able layer (pan / zoom / rotation / orbit) with built-in motion presets (static / slow_pan_right / slow_orbit / push_in / breathe)
• Pipeline ffmpeg `filter_complex` canonical for export; browser WebGL shaders for preview at perceptual tolerance (SSIM ≥ 0.98)

Scope — RFC-020

• Top-level `layers:` block — ordered list of layers
• Four layer types: `sketch` (wraps existing p5/canvas), `feedback` (the keystone), `texture` (medium overlay), `motion_graphics` (annotations / titles / markers)
• Feedback layer keystone primitive: `buffer[t] = fade * transform(buffer[t-1]) + source[t]`
  • `fade: 0.0` → Ikeda hard cuts
  • `fade: 0.95-0.98` → Akten accumulated trails
  • `fade: 0.99+` → Viola long temporal smear
• Per-layer envelopes / clocks / macros via RFC-014/016/017 polymorphism
• Blend modes: normal / multiply / screen / add / overlay / soft_light
• Texture bank in `visual/textures//` with same license + provenance discipline as LUTs
• Motion graphics templates: `data_label` / `title_card` / `progress_bar` / `marker` — triggerable on RFC-007 detected key moments
• Backward-compatible — legacy single-sketch recipes render unchanged via implicit `__legacy` layer

Dependencies

• RFC-014 (envelope primitive — drives post-FX and layer params)
• RFC-016 (clocks — per-layer rhythmic motion)
• RFC-017 (macros — cross-modal coordination between audio + visual)

Closes into

• ADR-044 — Visual identity + post-FX chain
• ADR-045 — LUT bank + provenance
• ADR-046 — Layer compositing primitive
• ADR-047 — Feedback layer + accumulator semantics

Notable design calls

• Identities grounded in artists, not generic moods — each identity composes coherent defaults from a real reference aesthetic rather than averaging into a generic look
• Single feedback primitive for three aesthetics — parameterising one number serves Ikeda / Akten / Viola without bespoke implementations
• Pipeline-canonical / browser-preview architecture — bit-identical export at the cost of preview-mode perceptual tolerance; the right trade for distribution