df20c392d8
Adds the "carries whatever it can reconstruct, verifies whatever it
carries" surface on top of the existing neural/codec WAI. All builds
green against this base (wai-rs all-features tests + clippy, wai-web
wasm, wai-spz-gen, wai-relay).
Reconstruct half — each a spec + conformance corpus + in-tab browser
sink that re-derives the corpus hash, over one wai.det.fixed64 floor:
- interactive worlds replay-equivalence (3 sim registrants,
relay multiplayer, session receipts, glTF + real-SPZ assets)
- spatial audio mixdown-equivalence
- haptics sample-equivalence
- state-feeds replay-equivalence (non-physics sim)
- avatars / digital humans pose-equivalence (+ telepresence)
- volumetric / 4D splats frame-state-equivalence (WebGPU EWA render)
Verify half (lever 4):
- asset provenance — signed, energy-accounted lineage for opaque
captured content WAI does not reconstruct; tamper-evident in-tab.
Cross-cutting: per-class JWP receipt profiles; a native energy meter
(IOReport via macmon, no sudo) emitting receipts with real measured
joules. Codecs gated behind a `codecs` feature (default on) so the
world/wasm sinks build without the C codec chain.
Excludes the separately-evolving neural subsystem (semantic path, GLC
rANS, ONNX tooling) to avoid reverting newer origin work.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
112 lines
5.5 KiB
Markdown
112 lines
5.5 KiB
Markdown
# WAI Extension: Avatars (Digital Humans)
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> Status: Draft. Phase 4 of the cargo roadmap. Motion as instructions:
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> ship a signed stream of joint transforms — a skeleton, not a video of a
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> body — and the sink skins a mesh by the deterministic pose. An avatar
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> is a skeletal world, so conformance is **pose-equivalence**, a special
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> case of replay-equivalence. Reference impl: the `world` feature of
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> `wai-rs` (sim `wai.world.sim.skeletal0`); corpus: `avatar-conformance/`;
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> live sink: wai.transaction.science/avatar.
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Keywords **MUST**, **MUST NOT**, **SHOULD**, **MAY** are RFC 2119/8174.
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## 1. Scope and model
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A `wai.avatar.pose` object is a **skeletal world**: the same `WWLD`
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container, op log, canonical ordering, causality, sealing, state hash,
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and receipt chain as interactive-worlds (see `interactive-worlds.md`),
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with the simulation step reduced to the **identity** (as with
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state-feeds). The bones are nodes; an animation / expression op stream
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sets joint transforms; nothing is integrated. A telepresence stream is a
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live world of one avatar — the op log that drives a multiplayer world
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drives a body.
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In scope: the bone model, the registered skeletal sim
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(`wai.world.sim.skeletal0`) and its mutation kinds, the statement that
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conformance is worlds' replay-equivalence over the pose, and the
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binding to a `wai.mesh.glb` for skinning.
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Out of scope: everything interactive-worlds already defines (normative
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here unchanged); the skinning algorithm and forward-kinematics
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composition (sink presentation — a pure function of the hashed pose +
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the hierarchy); a transport; blend-shape / morph-target semantics beyond
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joint transforms (a later registration may add them).
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Relationship to the core spec: a registration under interactive-worlds,
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not a new container. `media` takes the value `"avatar"`; the
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authoritative capability is `wai.avatar.pose`, carried in a `WWLD` whose
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contract names `sim = wai.world.sim.skeletal0`. The avatar's mesh is a
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content-addressed `wai.mesh.glb` asset (its armature + skin weights),
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bound to the rig like any other presentation asset.
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## 2. The bone
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A node is a **bone**: a parent reference plus a local TRS transform.
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Canonical field order (and therefore hash order) is exactly:
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| field | type | meaning |
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| `parent` | `[u8; 16]` | parent bone's node id, or all-zero for a root |
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| `translation` | `[Fx; 3]` | local translation (Q32.32) |
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| `rotation` | `[Fx; 4]` | local rotation quaternion `(x, y, z, w)` |
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| `scale` | `[Fx; 3]` | local scale |
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The canonical node serialization is `parent(16) | translation | rotation
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| scale` = 16 + 10×`i64` = 96 bytes. The default bone is the identity
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(zero translation, identity quaternion, unit scale).
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The floor stays **trig-free**: a rotation is carried as a quaternion, and
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the quaternion → rotation-matrix the sink uses for skinning is `+ − ×`
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only. Axis-angle authoring (which needs sin/cos) happens once, off-line,
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in whatever produces the op bytes — the canonical artifact is the `Fx`
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quaternion, and every sink replays it exactly.
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## 3. The skeletal sim — `wai.world.sim.skeletal0`
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Registers these mutation kinds; the `step` is the identity. All are LWW
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(a transform set rides the canonical total order — last canonical writer
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wins; there is no commutative transform set, so no SUM kind).
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| kind | payload | effect |
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|---|---|---|
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| `0x0001` CREATE | `parent[16] \| translation[3] \| rotation[4] \| scale[3]` | insert a bone; target MUST equal `mint_node_id(actor, lamport)` |
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| `0x0002` DELETE | *(empty)* | remove the bone |
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| `0x0010` SET_ROTATION | `rotation[4]` | set a joint's local rotation (the animation driver) |
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| `0x0011` SET_TRANSLATION | `translation[3]` | set a bone's local translation |
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| `0x0012` SET_SCALE | `scale[3]` | set a bone's local scale |
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An op targeting an absent bone is a **deterministic no-op**
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(interactive-worlds §6.4). `parent` need not name a present bone — a
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missing parent is treated as a root at FK time; the *hash* depends only
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on the stored values, so existence is irrelevant to conformance.
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## 4. Conformance — pose-equivalence
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> Given the same avatar container and the same signed op set, a
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> conforming sink MUST compute the identical BLAKE3 **state hash** at
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> every checkpoint — the per-bone local transforms, in node-id order — on
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> every machine, no tolerance parameter.
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This is interactive-worlds' criterion verbatim, applied to the bone
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state. The forward-kinematics composition into world space and the
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skinning of the mesh produce identical results on any two sinks that
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agree on the pose (a pure function of the hashed locals + the hierarchy),
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so they are legitimately left to presentation and excluded from the hash
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— exactly as `wai.mesh.glb` geometry is.
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## 5. Receipt (JWP profile)
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The interactive-worlds session receipt (`jwp-receipts.md`) applies
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unchanged: world identity over contract + tick-0 graph; the group's
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objects are the op batches, Merkle-bound; one Ed25519 seal over world
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hash + root + checkpoints + exact signed `work` + carried `joules_micro`;
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`parent_receipt_hash` chains a performance's seals into a timeline.
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## Appendix
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An avatar is the highest-bandwidth capture reduced to its instructions:
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a body in motion is a rig plus a stream of joint angles, and the standard
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carries the rig and the angles, not the pixels. Pose-equivalence makes
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the *motion* auditable — two parties to a call hold the same signed
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skeleton — while the *appearance* stays the sink's, skinned from a shared
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mesh. Sight (worlds), sound (mixdown), touch (sample), live state (feed),
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and now a moving body (pose) are one floor, one verification.
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