blender-mesh-authoring

name	blender-mesh-authoring
description	Create, modify, parent, and validate Blender mesh objects with stable names, direct data APIs, explicit modifier order, evaluated geometry checks, and reversible MCP transactions. Use for primitives, custom vertex/face meshes, transforms, parenting, bevel/solidify/subdivision modifiers, or topology repair when an out-of-box agent needs exact bpy mechanics rather than general modeling advice.

Blender mesh authoring

Use blender-python-execution for live MCP calls. Prefer direct mesh/data APIs for deterministic creation and reserve context-sensitive operators for edit-mode tools that have no practical data API equivalent.

Read references/bpy-mesh-recipes.md before creating geometry, changing parenting, or applying modifiers. Use caller-owned stable names and refuse to replace an incompatible existing datablock.

Authoring contract

1. Inspect the target object, mesh users, parent, collections, modifiers, mode, selection, and evaluated bounds before mutation.
2. Create or update only named caller-owned objects. Build custom topology with Mesh.from_pydata or bmesh; call mesh.validate() and mesh.update().
3. Set transforms absolutely. When reparenting without a visible jump, preserve matrix_world, assign the parent, then restore matrix_world.
4. Name modifiers, reject type collisions, and set their order deliberately. Do not apply a modifier unless destructive topology conversion was requested.
5. Call view_layer.update(), inspect the evaluated object, and run scripts/audit_mesh.py on every primary target.
6. Inspect a current viewport or inexpensive render for visible tasks. Numeric validity does not establish silhouette, proportions, or shading quality.

For MCP, prepend MESH_AUDIT_REQUEST = {"objects": ["GEO-subject"]} and append the complete audit script. For a saved derivative:

blender --background scene.blend --python scripts/audit_mesh.py -- \
  --objects GEO-subject GEO-trim

Require ok: true, finite evaluated coordinates and bounds, nonempty evaluated faces, valid polygon indices, and no zero-area evaluated faces. Boundary and non-manifold edge counts are reported for task-specific decisions: an open cloth or plane may be correct, while a printable solid normally requires both counts to be zero.

Failure rules

• Stop on missing targets, linked non-editable data, incompatible name collisions, non-finite transforms, invalid face indices, or empty evaluated output.
• Preserve selection, active object, and mode around operators. Never use selection as object identity.
• Do not clear the scene, apply all transforms/modifiers, merge by distance, or recalculate normals globally as an incidental repair.
• Save only to an absolute caller-selected derivative path; never overwrite the source implicitly.