93 lines
4.7 KiB
Markdown
93 lines
4.7 KiB
Markdown
# Timing model
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[Time selection](time.md) defines the current frame-rate representation.
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[The Lane Model](lane-model.md) defines the revised target for occurrence timing,
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source playback, sampling scope, and inverse editing. It supersedes conflicting
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proposals here; the sections below describe earlier implementation decisions.
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The source footage, authored drawings, generated face motion, and stage placement
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have different frame decisions. They share a clock but do not share one kept-frame
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list. `timing-handoff.md` records earlier implementation notes.
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## Frame spaces
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- A source frame addresses a decoded image and its measured face data. Keep the
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source cadence and, for variable-rate video, its presentation timestamp.
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- A timeline frame addresses authored keys in the clip or symbol's local space.
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- A stage frame is mapped through the symbol instance's offset and rate before
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local frame decisions are read. Moving a placement does not rewrite its keys.
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The analyzed source poses remain dense. A lower picture rate or a skipped pose
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never removes source data or shortens audio.
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## Head placement
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Analysis fits each source frame's rigid landmarks into one common head-local
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space. Its inverse is the measured head transform, stored densely on `:head`.
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The head node has one optional anchor map:
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```clojure
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;; no :anchors free movement: read measured frame f at f
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:anchors {0 12} ; one lock: use frame 12's transform throughout
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:anchors {0 12, 40 42} ; keyed locks: switch to frame 42 at local frame 40
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```
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A key is `(local change frame -> measured source frame)`. Its value holds to the
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next key. The map chooses position, rotation and scale together. Frame zero must
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have a key when the map exists. The dense transform blocks remain intact, so
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editing anchors is a small document change and re-freezing can replace the
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measurements without losing the anchor choices.
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A source image used for tracing should be registered with that image's measured
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stabilizing transform, then the selected head transform, then the authored
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`:place` placement the face carries. This makes the photo and head-local vectors share the same
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orientation and position. Tracing-photo selection is a separate editor address;
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it does not choose the head anchor.
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The prototype stabilizes into the shot's mean rigid pose and uses an early
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closed-mouth frame for raster framing. Those are internal analysis and framing
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choices. The authored head-anchor map above controls which measured head pose is
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shown over each range. It is independent of plate drawing starts.
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## Performance poses
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Generated mouth, eye, and brow channels can be sampled at a lower picture rate
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without retiming authored keys. The normal rule picks the latest available pose
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at or before a picture-grid time. A future performance policy may add important
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closed-mouth poses and store manual keeps/drops separately from the rate's
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proposal. Related parts should share a selected pose by default: a mouth outline,
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interior, teeth and generated visibility must not disagree about its frame.
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## Stage placement
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A symbol placement has optional pose-cut tracks, separate from head anchors:
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```clojure
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:playback {:tracks {:mouth {0 12, 8 27}
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:eye-r {0 0, 4 6}}}
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```
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These maps are also `(local change frame -> source pose frame)`. They select which
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baked/generated shape pose appears on that placement. Before the first explicit
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cut, normal generated motion continues. Cuts hold, without interpolation, until
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the next cut. A `[:node id]` track can override one shape in a shared group.
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Authored cels, transforms, and audio remain on their normal local time.
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The current implementation reads retained frozen channels. A separate resolved
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geometry bake is not implemented; when added, it must preserve addressable
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candidate poses so stage cuts can still select any of them.
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## Ownership
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| Choice | Owner | Current state |
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| --- | --- | --- |
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| Source frames and timestamps | Footage/analysis | Constant-rate frame indexing exists; variable timestamps remain future work |
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| Head anchor map | `:head` node | Implemented, stored with the node |
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| Trace frames (photo address) and origin | Face symbol's `:head` `:trace`, written through `:anchors` | Implemented, see `domain/trace` |
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| Showing the tracing photo, and its opacity | Face instance's `:underlay` | Implemented; a drawing aid, not keyed |
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| Generated picture-rate proposal and closure protection | Roto clip/symbol | Generated-only picture sampling exists; closure protection remains future work |
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| Stage pose cuts | Symbol instance | Implemented, stored with the instance |
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Preview and export use the same resolver for generated picture sampling and stage
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cuts. Export still emits every timeline frame at the clip's audio rate.
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