Maya modeling (hard surface, organic, props)

Expert modeling is purposeful topology: every loop exists for the silhouette, a highlight, a bake, a UV seam or a joint, and the model arrives downstream with nothing the next person has to clean. The agent works big to small, measures each stage with the toolkit, and looks at a metal highlight render before believing a surface. If a sibling skill named here is missing from your available skills, ask the user to install it (npx skills add scenario-labs/skills --skill <name>); unattended, proceed from tool schemas and flag the gap.

REQUIRED BACKGROUND: scenario-maya-expert (execution channel, review loop, 2027 version traps). Toolkit: scripts/mx_modeling.py (sys.path[:0] = ["<skills>/scenario-maya-modeling/scripts", "<skills>/scenario-maya-expert/scripts"]; import mx_modeling as MM), used with mx_audit, mx_validate, mx_review, mx_run. Not yet run in Maya: its pure-Python layer passed offline tests; every Maya call is pending tests/code/maya-modeling/run_all.sh.

Stance (the expert delta)

• Purpose first, then density. A still from CAD or booleans can skip clean topology; games, animation and close-ups cannot (Mario Elementza [00:00:32]). Minimum density is the narrowest feature, "the shortest distance between the two edges" [00:17:19]; then camera distance decides: low density needs redirected edges and pinches slightly (background), high density needs none (hero close-up) [01:09:20] [01:39:46]. Vertex count is the real cost: UV seams, hard edges and materials split vertices; a hard edge on a UV seam is free (Polycount).
• Clean uncut form, then cut. On flats, offset before cutting: the offset ring becomes the support loop; on curved parts, cut the support loop before the detail (Mario [00:16:13] [00:38:16] [01:19:49]).
• Even grid, never double; loops are the proof. Neighbor quads under 2:1 (Mario [00:08:31]); a breaking loop is an unsolved area, a loop that stops dead is a hidden double extrude [00:18:57] [00:39:22].
• Triangles: remove, solve, reinstate; n-gons never. On a cage, take triangles out, solve the rest, put one back only where the metal test holds; flats forgive, curves and deforming areas do not (Mario [00:20:36] [00:29:59]; Jessica Dru Johnson [01:12:33]). On a game low, triangles end loops locally (On Mars [00:10:29]). Cleanup fixes only lamina, non-manifold and zero-length geometry; n-gons by hand (FlippedNormals ToWRH4IXF7A [00:11:15] [00:11:50]).
• Cylinders in quarters, quad caps, ring loops only (Mario [00:57:43] [01:12:04] [01:14:16]; Pixar OpenSubdiv: no high-valence fans).
• The destination picks the edge-holding method, and subdivision lives in one place: Arnold renders Smooth Mesh Preview's state on top of its own iterations, so every save goes out with preview off (Arnold subdivision doc; FlippedNormals [00:24:00]). Creases are lost on export (antCGi RlNnp4qQIrU [00:28:12]).
• Deformation topology is the modeler's job. One control plus two support loops per joint (Jessica [01:15:51]), isolation loops bound controls [01:14:11], no pole on a deforming surface (antCGi QW8w15J00Ok [00:09:58]); prove a fix by bending two topologies with identical settings (antCGi x07USYlvu2o [00:16:24]).
• Hygiene is a delivery contract. Rebuild beats repair, unique short names, render stats at defaults; two-sided lighting hides flipped faces (FlippedNormals [00:08:31] [00:18:16] [00:02:35] [00:20:47]).

Establish first

Input	Changes	Default when silent
Destination	edge-holding method, triangulation, normals	game (PC/console) if an engine is named, else offline SubD
Budget	how much to strip	ask the lead; meanwhile anchor on On Mars' bands (grenade-class prop): hero seen large on screen 20k to 30k tris, secondary or tertiary props at 10 to 15% of the screen "much less" (no number given), background 10k or 5k. Report tris and engine vertices, justify each kept edge
Camera distance	narrowest feature kept, density vs redirection, corner softness	mid-ground, player can walk up to it [assumption, written in the report]
Deformation	loops per joint, no weighted normals, symmetry	none for props; characters: yes
Size, units	bevel widths, texel math	real size in cm, grounded; the Maya scene stays Y up even for a Z-up engine (FBX export or import converts the axis)
Pivot	engine placement	base center at the origin; a corner if the level snaps by corner (Epic)
Texture set	stacking, mirroring, UV2	2048, unique UVs (UVs belong to scenario-maya-retopology-uv)

Workflow

Every stage is a headless mx_run job that saves a new version with preview off; the GUI bridge is for playblasts and interactive tools (substitutes in references/procedures.md). Component lists cross stages only through MM.component_record and MM.carry_components, never by name or by an index read before a topology edit (P18).

1. Session and brief. cmds.about(version=True) (Smart Bevel changed in 2027.1 and 2027.2), units cm, Y up, brief in numbers (P1). GATE: assumptions written.
2. Blockout at real size. Primitives named at creation, stand on the grid, pivot per convention, freeze, delete history (P2). GATE: mx_audit frozen, no default_name or duplicate_short_name, dimensions within 2% [added]; silhouette and clay sheets compared to reference.
3. Primary form, clean grid. Write down the narrowest feature (groove, recess wall, gap) and its width: the grid near it takes that spacing, the rest balances to it; decide density or redirection per corner from the camera distance. Close the biggest quads, balance, stress-test by adding loops (Mario [00:10:11]); curves with Edit Edge Flow (antCGi [00:16:04]). GATE: MM.balance(m)["edges_over_limit"] == 0 before support loops; MM.cage_report(m): n-gons 0, every curved triangle removed or proven by the highlight review; loops continuous on the wire sheet.
4. Secondary forms. MM.extrude(faces, offset_cm=...) then recess (P3; refuses the empty extrude); openings from one quad; cylinders with MM.cylinder_sides_for and MM.build_quad_cylinder (P4), support loops cut before the opening; or polyCBoolOp on manifold meshes, then Smart Bevel (P5). GATE: zero-length edges, coincident pairs, non-manifold all 0.
5. Edge holding, per destination:
   • SubD hero or bake high, portable: support loops (offset rings, beveled-cube corner routing, Mario [00:44:24]).
   • SubD staying in Maya, Arnold or USD: creases, one method, values at or below render levels (MM.crease, MM.crease_report, P6).
   • Game low: chamfers with MM.bevel (Smart Bevel after booleans, legacy Fractional on clean quads) plus MM.weighted_normals, or hard edges on UV seams and a baked normal map (Polycount).
   • Still only from CAD or booleans: Smart Bevel, no retopology. GATE: MM.cage_report(cage)["ready_to_smooth"] (hard edges 0, since a faceted patch is a hard edge, Mario [01:28:38]; no fan caps; 6+ poles justified); MM.highlight_review(..., subdiv=n) stripes continuous across every cut; bevel problems empty; crease_report clean.
6. Game low and bake prep (P10). MM.smooth_copy the high; duplicate the cage and reach the low only by deleting edges (MM.flat_edges off the silhouette, loops ended with triangles); radius edges on round corners, evenly spaced, one on the crest (On Mars [00:12:50] [00:26:34]); parts touching the body welded in or their hidden faces deleted (Polycount: contiguous low); MM.shrink_wrap; MM.set_hard_by_angle(low, 45); MM.triangulated_copy(low, toward=high) for bake and export. GATE: MM.deviation recorded, silhouettes overlap, tris in budget, engine vertices reported, each separate shell (polyEvaluate(shell=True)) justified, diagonals_wrong_after == 0.
7. Characters: deformation check (P13). Loops across wrist and ankle, lids and lips with matching counts, mouth-corner loop under the cheek, neutral face (antCGi; Jessica [01:00:30]). GATE: MM.bend_test shows no flips and no regression against the previous topology; restored true.
8. Hygiene and handoff (P14, P15). MM.cleanup_technical, MM.inverted_shells, MM.handoff_report(roots, out, to=...), mx_validate.validate(profile="model", fix=SAFE_FIXES + ("render_stats",)), report again, save a new version. GATE: report ok; cleanup ok; 0 inverted shells; preview off; pending items named; sheets opened.

Numbers

Value	Setting	Relative to / source
Neighbor quad size	under 2:1	base grid, support loops excluded (Mario [00:08:31])
Minimum density	spacing = narrowest feature	balance the rest to it (Mario [00:17:19])
Cylinder sides	20, 24, 28, 32	multiples of 4, aligned with the cut (Mario [01:12:04])
Round feature on a cage	about 6 spans hero, 4 background	OpenSubdiv
Valence	4 regular; flag 6+; GPU limit about 27	OpenSubdiv
Radius edges on a visible round corner	more than 2 to 3, even spacing, one on the crest	On Mars [00:25:29] [00:26:34]
Loops per joint	1 control + 2 support; knuckles 3	Jessica [01:15:51] [01:17:34]
Crease	Maya value N creases N levels; above 5 rarely; 10 tears under displacement	Maya Help; OpenSubdiv
Smart Bevel	Width world units; Depth 1 chamfer, 0.5 rounded; 1 segment hard, 2 to 3 typical	Maya 2027 Help
Legacy bevel defaults	Fractional, 1 segment, depth 1, smoothing angle 30; 2 segments on box corners	Maya 2027 Help; FlippedNormals [00:18:18]
Hard edges on a mechanical low	above about 45 degrees, and on UV seams	Polycount
Grenade budgets	cage 61k, low 24k; "polygons" is about half the tris	On Mars [00:04:21] [00:21:31]
Sheet share	surface cm² x (px/cm)² / map px² (12,800 cm² at 10.24 = 32% of 2048²)	arithmetic [added]
Subdivision cost	x4 polygons per level; preview levels + Arnold iterations add up	Arnold doc

Quality gates

Measurable, per mesh: mx_audit.verdict(mx_audit.audit(m, texture_size=2048), "game" | "film" | "subd", max_tris=budget) has no error, plus the MM checks named in each GATE; scene: mx_validate.validate(profile="model") no fail; together: MM.handoff_report. Visual, opened every time: mx_review.review sheet (silhouette vs reference, clay, wire loops, normals); MM.highlight_review with focus= closeups on every cut (kinks, dark streaks, wobbles are pinching, Mario frames 00:12:45, 01:38:42); high and low silhouettes side by side; in a GUI session, two-sided lighting off or backface culling. Judge with references/critique.md.

Common mistakes

Mistake	Looks like	Fix
Empty extrude	loop stops dead; crease in smooth preview	MM.extrude refuses it; mx_audit zero-length edges
Vertical cuts on a cylinder	wobbling highlight	rebuild with more sides, or smooth once
Fan cap	dimple at the cap center	cage_report fan poles; MM.build_quad_cylinder
Hard edges left on a cage	faceted patches when smoothed	polySoftEdge(angle=180) until cage_report hard edges 0
Cleanup with tessellation on	random triangulation	MM.cleanup_technical; n-gons by hand
Preview on at save, plus Arnold iterations	heavy files, huge slow renders	MM.subdiv_setup in one place; mx_validate smooth_preview
Creases on an FBX asset	sharpness gone in engine	bevel, or ship a smoothed copy
Weighted normals on a deforming mesh	shading stuck while skinning	static meshes only
Hard edges off UV seams	vertex count up, nothing gained	seams on hard edges (hard_edge_components)
Whole shell inside out	black with two-sided lighting off, fine with it on	MM.inverted_shells, reverse
V-snap without weld	seam in smooth preview	Target Weld; coincident_vertices
Round high corner, sharp low	bake artifacts	radius edges on the low, one on the crest
Low left floating, or parts intersecting	bake misses, overlap errors, UV space on hidden faces	MM.shrink_wrap; weld parts in or delete hidden faces
Engine picks the diagonal	ridge instead of valley, zig-zag shading	MM.triangulated_copy(toward=high), export triangulated
Component ids reused after an edit	wrong edges deleted, silhouette lost	MM.carry_components refuses; re-derive
Spiral limb loops, pole on the chest	muddy weights, kinks	concentric loops, reroute the pole

Handoffs

• Receives the brief from scenario-maya-expert; sculpts from scenario-zbrush-expert (check scale, ZBrush has no units; orientation; locked normals); generated meshes from scenario-3d (reference or bake high only).
• Delivers to scenario-maya-retopology-uv (UVs, bake prep): a new version <asset>_model_v###.ma, <asset>_GRP with _geo meshes (engine names such as SM_ and UCX_ for games), the cage, <asset>_high with floaters separate and castsShadows off for AO (Polycount), the low if built, handoff_<to>.json with UVs pending, the hard-edge list for UV cuts, and the sheets looked at. Manifold after triangulation too: Unfold3D refuses non-manifold meshes and unfolds a triangulated copy (P17).
• Delivers to scenario-maya-rigging (deformation-ready): to="rigging" clean (X symmetry, no locked normals, no history), grounded and centered, eyes separate and looking ahead, symmetric parts combined, bend_test numbers (antCGi e74K checklist).
• Delivers to scenario-maya-lookdev (film SubD): subdivision set in one place, crease sets named with values, preview off. FBX export goes to scenario-maya-pipeline-scripting.

Maya 2027 notes

• Smart Bevel (polySmartBevel, 2027): world-unit Width, Depth profile, Filter default Selected Edges; output differs 2027.0, .1, .2; flags unknown until probed (MM.bevel records attr_map). Its box-corner behavior is untested: the 2-segment rule comes from the legacy bevel, so read the problems census. Old bevel is "legacy bevel", with Filter attributes and intersection-only bevels on booleans since 2025.
• Shift+drag is "Shift Extrude" (2025); Smart Extrude stitches overlapping faces, Edit Mesh > Extrude does not. Booleans: polyBoolean (2023), 3ds Max engine (2025.3), Volume mode (2026).
• Smooth Mesh Preview is OpenSubdiv Catmull-Clark; Crease Tool and Crease Sets are exclusive per component.
• New scenes default to OpenPBR Surface; the highlight review uses aiStandardSurface.
• Reduce is decimation, not retopology; Quad Draw is interactive only.
• FBX import can bring user normals (2027); imported normals may arrive locked (Mesh Display > Unlock Normals).
• macOS keys: Ctrl is Control, Alt is Option.

References

• references/procedures.md: full code P1 to P18 with test paths. Load before writing any modeling code.
• references/critique.md: the judging rubric. Load at every gate and before reporting.
• references/expert-notes.md: each expert's reasoning, timestamps, disagreements. Load for an unfamiliar asset type or a judgment call.
• references/gui-paths.md: menus and hotkeys for a GUI or computer-use session.
• references/sources.md: sources, credentials, best timestamps.