- applyU now maps u to a shared global frame index uGlobal in [0, maxT-1];
each panel clamps to its own (T-1), so a shorter timeline pads its last
frame while the longer one finishes — both advance at the same wall-clock
tempo instead of rescaling their timelines.
- tick() keeps u as a float closure variable; reading it back from the
integer-step scrubber was quantizing du to 0 at slow tempo + high T
(1600ms/frame, T=24: du ≈ 4e-4 → round to 0 on scrub), stalling playback
after one frame.
Default is smooth (lerp each point between adjacent frames); a motion:step
toggle preserves the snap-to-frame behaviour. Points missing in either
adjacent frame are hidden during the transition to avoid pop-in.
- /compare page renders two ortho-camera panels fed by /api/runs/{stem}/frames.json
- shared controls: play/pause, scrubber, speed (0.5-4x), axes sync (independent/locked)
- linked hover: picks nearest point in one panel, highlights matching point_id in other
- add/remove-jitter nulls handled via per-frame packed positions + setDrawRange
- independent error states per panel; theme-aware colors via themechange event
- per-run checkbox when embedding HTML exists; cap at 2 selected
- sticky 'compare selected' button opens /compare?a=&b= in new tab
- selection state persists across the 3s htmx poll via a Set keyed by stem
- /compare stub validates stems, renders scaffolding (three.js UI next)
