Author a pose via IK and bake

Author a pose via IK + bake

The contract this workflow enforces: authoring solves IK, runtime never does. A pose is solved once in Blender, baked to plain FK rotations, and stored as data the runtime replays. Runtime IK is a per-frame solver fighting your animation blend; baked FK is a lookup.

Works over a live Blender session when a Blender MCP is connected (probe it first — e.g. a get_scene_info-style tool); otherwise write the same steps as a headless bpy script the user runs with blender --background --python.

Preconditions

• A rigged character GLB and an item GLB whose grip points are marked with Socket_* empties (e.g. Socket_Grip for the primary hand, Socket_Foregrip for the support hand). No sockets → author them first (/hologram:glb-standards).
• A pose registry in the project — wherever this project persists authored poses (a Python dict module, JSON file, or similar that its export scripts read). If none exists, propose one: a POSES = {name: {bone: {"rotation_euler": (x, y, z)}}} module the export script iterates.
• The pose name must be new; overwriting an existing pose needs explicit user approval.

Workflow

1. Snapshot the scene. Record existing object/action/collection names so cleanup can remove exactly what this run adds. The live scene is a sandbox — the only persistent outputs are the registry entry and the re-export.
2. Import into a fresh collection (fail if a previous run's collection is still there). Import the character, then the item; parent the item to the hand bone (parent_type = "BONE", matrix_parent_inverse from the inverted world @ pose-bone matrix) so it rides the rig exactly as it will at runtime.
3. Place IK targets at the sockets. One empty per involved hand, positioned with the socket's matrix_world. Two-handed items: primary hand → Socket_Grip, support hand → Socket_Foregrip. One-handed: primary only.
4. Constrain the hand bones. An IK constraint per involved hand, targeting its empty, chain_count = 3 (hand → forearm → upper arm). Optional pre-pose before solving (e.g. dip the neck for an aim stance).
5. Screenshot and get approval. Show the solve; accept nudges to the IK targets ("move the left target up 2cm") and re-screenshot until the user approves or cancels. Cancel → cleanup, write nothing.
6. Bake. First force full keying — Blender 5.2's "Only Insert Needed" preference silently skips redundant keys and melts hold poses: bpy.context.preferences.edit.use_keyframe_insert_needed = False. Then bpy.ops.nla.bake(frame_start=0, frame_end=2, only_selected=True, visual_keying=True, clear_constraints=True, bake_types={"POSE"}).
7. Read the resolved rotations. For every bone the bake keyed, take pose_bone.matrix_basis.to_euler("XYZ") in degrees, rounded to 2 decimals (sub-centidegree differences are imperceptible and the diff stays readable). Pick ONE Euler order and use it everywhere — mixing orders corrupts poses.
8. Persist to the registry in the project's existing format, with a comment header (what, why, authoring date). Then clean up: delete the run's collection, its objects, and the temporary baked action.
9. Re-export the character through the project's export path so the pose ships in the GLB, then tell the user how to verify (equip the item; the pose should match the approved screenshot).