mesh-automasking-settings

Mesh automasking settings move

Pathology witness for the 5.2 move of sculpt automasking RNA off Brush into MeshAutomaskingSettings. There is no geometry and no gallery still (same class as vse-linear-modifiers, ngon-triangulate).

Follows the version-gated assertion shape of gn-modifier-inputs (per-version contract, exit 0 on every matrix leg). Scaffolding matches cross-version-property-delete (check() returns, argparse naive-API flag, FATAL wrapper). That example does not version-branch, so the gate itself is copied from gn-modifier-inputs, not from del.

Headless: factory-empty has zero brushes. The script creates one with bpy.data.brushes.new("ProbeBrush", mode="SCULPT"). mode="SCULPT" is load-bearing on 5.2: a default-mode new(name) leaves mesh_automasking_settings is None.

Subset (3 of the 18 attributes; the full map is below): use_automasking_topology and use_automasking_cavity keep their identifiers after the move; cavity factor does not (Brush.automasking_cavity_factor vs MeshAutomaskingSettings.cavity_factor). That pair covers the location move and the nested identifier shortening.

What it witnesses: bpy.types.MeshAutomaskingSettings is absent on 4.5.11 and 5.1.2 and present on 5.2.1. Old Brush.use_automasking_* / Brush.automasking_* getattr works on 4.5/5.1 and is AttributeError on 5.2. Reading .mesh_automasking_settings (with a Brush fallback) works on all three.

What failure each check would catch:

• exit 3 — SCULPT brush never landed
• exit 4 — MeshAutomaskingSettings type presence wrong for this Blender
• exit 5 — old Brush attributes missing when required (--assume-brush-attrs on 5.2 lands here)
• exit 6 — old Brush attributes still present, or mas pointer is None, on 5.2+
• exit 7 — current-location read raised or returned the wrong types

--assume-brush-attrs is the falsifier: skip the version gate and demand the 4.5 Brush RNA. It exits 0 on 4.5.11 and 5.1.2 (the old API still works) and 5 on 5.2.1. That is unlike --same-axis, which is red on every binary.

No SMOKE_SKIP. Every matrix leg exercises the contract.

Who hits this

Sculpt add-ons, brush-preset importers and tool-setting UIs that read or write brush.use_automasking_* / brush.automasking_*. On 5.2 the first such access raises AttributeError: 'Brush' object has no attribute .... A panel that draws it disappears from the UI, and an importer stops halfway through a preset.

Two traps on the way to fixing it:

• The prefix rule is not uniform. The ten use_automasking_* booleans keep their identifiers on the new struct. The eight automasking_* values drop the prefix, so a blanket getattr(mas, old_name) port breaks on exactly those eight.
• A brush made without a mode has no settings struct. bpy.data.brushes.new(name) returns a brush whose mesh_automasking_settings is None on 5.2. It must be created with mode="SCULPT". A reader that trusts the pointer then dereferences None.

The version-safe reader is the one this example asserts (read_current): take .mesh_automasking_settings when it exists and is not None, otherwise fall back to the Brush attributes. Writes go through the same struct and round-trip: setting cavity_factor and use_automasking_topology on it reads back unchanged on 5.2.1.

Full attribute map

Measured by listing Brush RNA on 4.5.11 and 5.1.2 (18 automasking properties, identical on both), and MeshAutomaskingSettings RNA on 5.2.1 (19 properties).

4.5 / 5.1 Brush.	5.2 Brush.mesh_automasking_settings.
use_automasking_topology	use_automasking_topology
use_automasking_face_sets	use_automasking_face_sets
use_automasking_boundary_edges	use_automasking_boundary_edges
use_automasking_boundary_face_sets	use_automasking_boundary_face_sets
use_automasking_cavity	use_automasking_cavity
use_automasking_cavity_inverted	use_automasking_cavity_inverted
use_automasking_custom_cavity_curve	use_automasking_custom_cavity_curve
use_automasking_start_normal	use_automasking_start_normal
use_automasking_view_normal	use_automasking_view_normal
use_automasking_view_occlusion	use_automasking_view_occlusion
automasking_boundary_edges_propagation_steps	boundary_edges_propagation_steps
automasking_cavity_blur_steps	cavity_blur_steps
automasking_cavity_curve	cavity_curve
automasking_cavity_factor	cavity_factor
automasking_start_normal_falloff	start_normal_falloff
automasking_start_normal_limit	start_normal_limit
automasking_view_normal_falloff	view_normal_falloff
automasking_view_normal_limit	view_normal_limit
—	cavity_curve_op (new in 5.2, no Brush counterpart)

On 5.2.1 the only automasking-named property left on Brush is the mesh_automasking_settings pointer itself.

Re-verified

Measurement	4.5.11	5.1.2	5.2.1
bpy.types.MeshAutomaskingSettings exists	no	no	yes
Automasking properties on Brush	18	18	1 (the pointer)
mesh_automasking_settings, mode="SCULPT"	no attribute	no attribute	struct
mesh_automasking_settings, default mode	no attribute	no attribute	None
Brushes in factory-empty	0	0	0
default exit	0	0	0
--assume-brush-attrs exit	0	0	5

Exiting 0 on 4.5.11 and 5.1.2 under the falsifier is correct by design. The old attributes still exist there, so the naive read works; the falsifier exists to fail where they were removed.

API reference

• bpy.types.MeshAutomaskingSettings (5.2 only)
• bpy.types.Brush (4.5 LTS, where the use_automasking_* / automasking_* attributes live)
• BlendDataBrushes.new — the mode argument

Run

blender --background --python mesh_automasking_settings.py --
blender --background --python mesh_automasking_settings.py -- --assume-brush-attrs

Exit codes

Per-script sequential checks. 9 is a valid check code; there is no rule against it.

Code	Meaning
0	Success
1	Uncaught exception (FATAL wrapper)
2	argparse / usage
3	SCULPT brush was not created
4	MeshAutomaskingSettings type presence wrong for this version
5	Old Brush automasking attributes missing when required (--assume-brush-attrs on 5.2)
6	Old Brush attributes still present, or mas is None, on 5.2+
7	Current-location read raised or returned the wrong types

The blender-smoke workflow runs the check on Blender 5.2 LTS and 4.5 LTS (5.1 on the weekly cron, the needs-5.1 PR label, or manual dispatch). Smoke does not pass --assume-brush-attrs.