Anim: Slice E — VAT export family (skeletal, rigid-body, mesh-anim, morph)

[fernandotonon]

Parent epic: #517
Subsumes: #371 (the existing skeletal-VAT issue — design preserved, broadened into a family)

Goal

A single VAT exporter family that covers the four real-world VAT variants. One CLI/MCP surface (qtmesh vat), one inspector panel, one set of encoders and sidecar conventions — pluggable samplers per variant.

Scope

• VATBaker as planned in Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371 becomes the shared scaffold (encoders RGBA8 / RGBA16 / EXR, JSON sidecar, target variants agnostic/Unity/Unreal/Godot). The four samplers plug into the same baker:

  1. Skeletal VAT — the existing Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371 design: step animation state, read post-skinning vertex data via entity->_getSkelAnimVertexData(). Slice 1–4 of Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371's plan carry over verbatim.
  2. Rigid-body VAT — one quaternion + pivot per "chunk" (e.g. each submesh or a custom chunk grouping). Useful for destruction (Houdini RBD), animated mechanical pieces. Each chunk occupies one texel per frame in a tiny texture; the runtime shader applies quat * (vertex - pivot) + pivot.
  3. Mesh-anim VAT — bakes the vertex-animation tracks from Slice B (Alembic / VAT_POSE) into VAT textures. The sampler reads from VertexAnimationManager instead of entity->_getSkelAnimVertexData().
  4. Morph VAT — bakes morph-weight-driven mesh deformation from Slice A. Sampler resolves morph weights → vertex deltas per frame.

• Shared: encoders, JSON sidecar shape, target variants (agnostic/Unity/Unreal/Godot), CLI/MCP surfaces, QML "Bake VAT" panel, async progress, Sentry breadcrumbs.

• CLI: qtmesh vat model.fbx --mode skeletal|rigid|mesh-anim|morph --anim Walk --fps 30 --encoding rgba8|rgba16|exr --target agnostic|unity|unreal|godot -o out/.

• MCP: bake_vat tool with a mode parameter.

• Sidecar JSON: extends Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371's schema with a mode field and mode-specific extras (chunk count + pivots for rigid; track ID for mesh-anim; target names for morph).

Acceptance Criteria

• All four modes produce correct textures + sidecars; baked playback in a test Godot scene visually matches live playback in QtMeshEditor at RGBA16 or better.
• Skeletal mode is bit-identical to Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371's outputs (regression-tested).
• Rigid-body mode bakes a Houdini-style destruction cache (test fixture) and a shader template plays it back.
• Mesh-anim mode bakes an Alembic cache (test fixture, depends on Slice B).
• Morph mode bakes a facial-expression sequence (depends on Slice A).
• One inspector "Bake VAT" panel handles all four modes with a mode picker.
• All four targets (agnostic / Unity / Unreal / Godot) produce correct axis convention + sidecar files.
• CLI/MCP/GUI parity.
• Sentry breadcrumb file.export with vat_mode tag.

Effort

• Skeletal sub-slices (1–4) follow Exporter: Vertex Animation Texture (VAT) — bake skeletal anim into RGB textures #371's plan: ~14 days as planned there.
• Rigid-body sampler: ~5 days.
• Mesh-anim sampler: ~3 days (after Slice B lands).
• Morph sampler: ~3 days (after Slice A lands).

Total: ~25 days spread across multiple PRs. Each mode is its own PR.

Note

Closes #371 when the skeletal sub-slices land. The remaining mode samplers can each be tracked as a sub-issue of this slice if convenient.