ADR 0002 Render Path

ADR 0002 — Avatar render path

Status: Accepted (interim) — 2026-08-02
Context: M7 must choose local WebGL vs streamed frames for the kiosk avatar.

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Decision

Ship local HTMLAudioElement playback now; keep local WebGL TalkingHead as the target when a GLB is available. Do not stream rendered frames from the AI server in Phase 1.

Phase 1 avatar is the 2D ComStar starburst (live SVG) — see Kiosk & Avatar.

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Rationale

• Audio sink is already the kiosk (ADR 0001); lip-sync and audio must share one clock.
• Streaming video of an avatar adds LAN bandwidth and another failure mode without helping the walk-up demo before a GLB exists.
• Pi 4B + Chromium can play WAV/HTTP audio reliably at 1024×768; WebGL fps for a full TalkingHead GLB is still to be measured.

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Consequences

• terminal/kiosk/avatar.js uses HTMLAudioElement until assets/comstar.glb (or avatar.model) is present.
• CONTRACTS §9 documents both paths; lip-sync acceptance remains an open UAT.
• Revisit if Pi WebGL fps < 24 sustained with the chosen GLB — then consider a lighter mesh or baked viseme sprites, not server-side streaming.

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Measurement TODO

On comstar-ai, load the GLB in Chromium kiosk and record avg/1% fps for 60 s idle + 10 spoken lines. Paste results into Baselines when available.

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Related

• Kiosk & Avatar
• ADR Index