ZBrush hard surface

Hard surface is judged as a result: it reads as manufactured when every edge is clearly straight or clearly curved, planes carry an even highlight, edges are wide enough to catch light and every part could be built (Plouffe, Klimer). The agent builds that language from deterministic operations (primitives, Live Boolean stacks, polygroups as the crease plan, Dynamic Subdivision numbers, ArrayMesh, Panel Loops) and uses clicks and strokes only where nothing else exists. 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-zbrush-expert (bridge, stroke engine, review loop, 2026 traps). Toolkit: scripts/zb_hardsurface.py (import sys; sys.path.insert(0, "<this skill>/scripts"); import zb_hardsurface as hs, then hs.hs_call("new_part", "cube")), built on the lead's zb_ops, zb_review, zb_audit and zb_stroke. Nothing in it has run in ZBrush yet.

Stance (the expert delta)

• Polygroups are the crease plan. Groups By Normals at 45 degrees (33 catches softer planes, 60 misses edges), Mirror And Weld, UnCreaseAll, Crease PG (Pavlovich; Plouffe). Crease first, a loop only where the falloff must be local. Crease PG after later edits recreases borders you softened on purpose: regroup, or crease by angle.
• The gap SmoothSubdiv minus CreaseLvl sets the edge. 0 reads razor, "very CG"; the closer CreaseLvl sits to SmoothSubdiv, the tighter the edge, so 4/3 is tighter than 4/2 (hs.edge_width). Pavlovich works at 3/2 and bakes 4/2; Plouffe keeps CreaseLvl 3 over a razor 4 and calls 2 too soft. Deciding condition: render both under metal, keep the widest edge that still looks planned.
• QGrid is for boxy blocks (it facets arcs). Curved spans take Smooth Subdiv plus Crease Tolerance, tuned per span: 22 held Pavlovich's arch; too low creases the arc's small angles.
• Booleans need clean inputs (Live Boolean doc; Pavlovich): watertight, no coplanar faces, similar density, low Dynamic levels, nothing partly hidden. DSDiv on, one Start group per separate part, then ZRemesher Detect Edges at Half. Creases, UVs, levels and layers die in the boolean; polygroups survive.
• Keep cuts and repeats live. ArrayMesh the cutter, not the result. Instanced fasteners (NanoMesh, ArrayMesh) make a late "flathead, not Phillips" one Edit Mesh swap; per-seat imports cost one call per seat.
• Straight or curved, never in between (Plouffe). Polish planes, then edges, then corner softness, sharp to smooth; never mix sharp and round edges close together; one cavity along a border sells a separate plate.
• Function and camera set the detail (Klimer): how it is made, where power flows, one fastener family, repeated angles identical. Validate twice in engine: the block (500 to 40k polys) with the rig, then a decimated high under 1M points. Unseen interiors and undersides stay filled or simple, sold by dark AO (Pavlovich).
• Micro detail waits for sign-off, on 3D layers (Klimer): a negative strength carves in, duplicating doubles, and a layer dies with any topology change, so layers come after the last boolean, remesh or Apply [added].
• Mirror And Weld always copies negative X onto positive X. Good half on +X: Deformation Mirror first (Pavlovich, Plouffe). Slice, Trim and BRadius ignore symmetry, so every one-sided edit ends here.

What the agent can and cannot do here

Deterministic (script it)	Click or stroke [verify]	GUI only, or substitute
Primitives, Unify, placement (new_part, place, import_part); Live Boolean roles (set_roles, roles_from_groups), DSDiv, Make Boolean Mesh, Show Coplanar and Show Issues	ZModeler: a saved brush or 2026 preset holding the action and crease option, one canvas_action at click_target (a drag the first time; a tap replays)	Clip, Trim, Slice, Knife (Ctrl+Shift drag; press_key is broken): boolean cutters, fitted_split_groups, DynaMesh Groups on a group outline, a ZScript IKeyPress wrapper (scenario-zbrush-automation)
Dynamic Subdiv, CreaseLvl, CTolerance, Crease PG, Crease Bevel, Apply	NanoMesh insert: one click on a face of the target group, or on a front-facing plane (the shipped macro's routine)	Gizmo deformers: Deformation sliders on an axis-aligned part
Groups By Normals, Mirror And Weld, Panel Loops, GroupsLoops, ArrayMesh, NanoMesh sliders, MeshFromBrush (fastener_from_brush), masks (mask_fillet), ZRemesher, DynaMesh, Decimation	IMM: a synthesized Dots stroke, or Curve Mode on script curves; imm_ready first	Retopo brush, Mask By Polypaint dialog, freehand masks, hPolish planing (weak strokes)

Establish first

Input	Changes	Default when silent
Destination	game (bake to a low), film, print collectible, concept read	game asset baked to one 2048 map (Pavlovich's pistol)
Camera	first person and ADS, third person, turntable, print framing	third person; detail sized to what reads there
Budget	low-poly triangles, map size, high-poly cap	report counts and ask; never invent a budget
Function sheet	how it opens, vents, power, how it is made, fastener family	write one before blocking (Klimer)
Scale	rigged: real scale in the block; concept: proportion	Unify (about 2 units), Z forward, perspective off (Chervenka); mm briefs via to_tool_units
Moving parts	a hinged visor stays a separate part and Start group	separate
Painter handoff	Substance Bridge, or OBJ plus an external bake	ask; both are below

Workflow

1. Setup. Proxy or concept as a SubTool; Unify, Z forward, X symmetry; versioned ZTL before every boolean, DynaMesh, ZRemesher and Apply (no undo from Python). GATE: longest bbox side about 2; ZTL on disk.
2. Block. new_part and place, or import_part from a DCC block; body first, cutters below. GATE: forms sheet (zb_review.review) against the concept; a rigged asset's block OBJ checked in engine with the rig before detailing.
3. Shell. Deformation sliders on primitives, subtractive boxes for openings, Make Boolean Mesh, zremesh_recipe("after_boolean"). The sculpted route (DynaMesh 128 to 176, hPolish, TrimDynamic) is concept only. GATE: hygiene(obj) ok (it stands in for Check Mesh, which reports through a note); PolyFrame shows even quads.
4. Crease plan. crease_by_groups(45), dynamic_subdiv(intent="working"); arcs crease_by_angle, tuned per span. Loops and insets made with ZModeler take their crease at creation (zmodeler_plan: Insert EdgeLoop "Crease"; Inset "Crease New Edges" crisp, "Crease Inner Poly" rounded; defaults are Do Not Crease). GATE: check_crease; metal sheet (review_sheets) shows soft, light-catching edges, no scalloping, symmetric polygroups.
5. Cuts and vents. Cutters new_part(..., op="sub") through the surface, never flush; Smooth 3 / CreaseLvl 2 plus crease by angle; array_mesh on the cutter. GATE before: stack_report()["problems"] empty, coplanar_report clean, Show Coplanar snapshot has no red, array_plan walls ok. Then make_boolean_mesh (short timeout). GATE after: UMesh SubTools equal Start groups; Show Issues snapshot clean; recrease (Crease PG unless a border was softened on purpose); hygiene before ZRemesher. Any one-sided edit: mirror_report, mirror_weld(keep=...), then mirror_check on exports before and after.
6. Panels and fitted parts. Plan panels as polygroups first. Real separations: Panel Loops with Plouffe's recipe (panel_loops). A visor or hatch that fits its opening: one cutter used twice (fitted_split_groups: Intersect in one Start group, Subtract in the other), or DynaMesh Groups on a group outline. Seams: a thin subtractive cutter from border_polylines plus curve_mesh [verify]. Masks: mask_fillet (Klimer's blur, invert, repeated). GATE: split_copy("groups") counts panels; gaps constant on the sheet.
7. Hardware. One family. ArrayMesh rows; radial sets as ArrayMesh Rotate 360 then array_commit("nano") with ZRVar variation (Chervenka); a part from an IMM without a drag: fastener_from_brush; no face where a bolt goes: a helper plane. A port across a seam: seam_port_groups (Pavlovich). Exact runs: spaced_points. GATE: count, orientation and the same fastener everywhere on the sheet.
8. High-poly commit. bake_split(): Apply at 4/2 on a copy, Dynamic off on the original. Exact chamfer widths: Crease Bevel width or a boolean chamfer, since Polish only gives the minimum (Polycount). GATE: levels = 1 + Flat + Smooth; edge_language has no ambiguous lines; plane_flatness no wobbly groups; pinch_report flags nothing.
9. Micro detail (after sign-off). Layers per region (Tool:Layers:New; procedures P15). GATE: layer_safe(recorded, zb_ops.stats()) before and after each pass.
10. Low poly and handoff. Dynamic-off cage; ZRemesher per part (zremesh_recipe("part")); quick static prop: dynamesh_visible(res) then one decimate_percent; or Maya or Blender. Klimer's ZRemesher plus auto-reduction gave "the nastiest mesh I've ever shipped". Painter routes (scenario-zbrush-retopology-export runs them): Substance Bridge Low & High plus Auto-Bake plus Send PolyPaint (bridge_preflight), or native Unwrap with crease seams (unwrap_creases) then OBJ. GATE: zb_audit.verdict(..., "game"); animated parts separate.

Numbers

Value	Use	Source
Groups By Normals 45 (33 softer, 60 misses)	crease plan	Pavlovich; Plouffe
Smooth/Crease 3/2 working, 4/2 bake, 4/3 tight, 4/1 soft	edge width	Pavlovich; Plouffe
Crease Tolerance 45 (22 on one arch)	crease by angle	Pavlovich
Faces x4 per QGrid, Flat or Smooth step; Apply levels 1 + Flat + Smooth	budgets	DSUB doc
Cutter cylinders 8, 12, 16, 24 or 32 sides; 36 to 140 before a DynaMesh bake	cutters	Pavlovich; Polycount
ArrayMesh Repeat 4 to 5	vents	Pavlovich
Panel Loops: Loops 1, Polish 0, Bevel 0, Elevation -100, Double, Ignore Groups	plates	Plouffe
ZRemesher Half + Detect Edges + Adaptive 0	cut-ready base	Pavlovich
Keep Groups, Smooth Groups 0, AdaptiveSize 25	part retopology	Chervenka
About 3 stars on a panel base	pinch budget	Plouffe
LazyStep 2 touching (his guess), 2.5 rivets; Curve Step 1 touching	IMM runs	Pavlovich; IMM doc
DynaMesh 176 exploration; 1000 game shell	resolution	Pavlovich
25k of 1.671M = 1.4 to 1.5 percent	one decimation pass	Pavlovich
10M polygons per SubTool	high-poly cap	Plouffe
Block 500 to 40k polys; review high under 1M points	engine checks	Klimer
2048 bake, 4 px padding	maps	Pavlovich

Quality gates

• Code: stack_report and coplanar_report clean; make_boolean_mesh()["ok"]; hygiene; check_crease; mirror_check; edge_language (no ambiguous); plane_flatness(obj)["wobbly"] empty; pinch_report; layer_safe; bridge_preflight; zb_audit.verdict.
• Visual: review_sheets: MatCap Gray from five views for forms; metal, square-on and 30-degree grazing for planes and edge width; PolyFrame for groups and dotted crease lines. Show Coplanar before and Show Issues after each boolean. Pinches: a low level with dark polypaint and a low-metal MatCap. Judge with references/critique.md.

Common mistakes

Mistake	Looks like	Fix
CreaseLvl >= SmoothSubdiv	razor CG edges	dynamic_subdiv(intent="bake")
QGrid on a curved shell	faceted arcs	QGrid 0, Smooth plus crease_by_angle
Cutter flush with the body	coplanar note blocks; holes	cut through; coplanar_report
No Start group or DSDiv off	part sewn to the body; faceted UMesh	set_roles(... start=True); dsdiv=True
Mirror And Weld, good half on +X	edit erased	mirror_weld(keep="pos"), mirror_check
Crease PG after softening borders	softened edges razor again	crease by angle, or merge groups first
Debris after cuts	ZRemesher fails	hygiene, hide debris, Del Hidden
IMM on a SubTool with levels	insert refused	imm_ready; level-free placeholder SubTool
Layer made before a topology change	layer no longer applies	layers after the last boolean or Apply
Force UV Auto-Unwrap on	every SubTool loses its UVs	bridge_preflight; off

Handoffs

• Receives: a concept and brief from the user; an AI mesh from scenario-3d; a DCC block from scenario-maya-modeling or scenario-blender-hard-surface (OBJ, quads and tris); a forms pass from scenario-zbrush-sculpting.
• Delivers: a versioned ZTL (high SubTools, Dynamic-off cages), OBJ per part with matching high and low names, stack_report and the last sheets; to scenario-zbrush-retopology-export for UVs (Unwrap with crease seams, UV Master), Substance Bridge or Multi Map Exporter bakes (a polypaint ID travels by Send PolyPaint or an MME Texture From Polypaint map; OBJ vertex color is not established) and the game low poly; the 2026.1 Retopo brush is a GUI step there; to scenario-maya-modeling, scenario-maya-retopology-uv, scenario-blender-retopology or scenario-blender-uv-baking for a hand-built low; polypaint IDs with scenario-zbrush-paint-render; print parts to scenario-zbrush-pose-print.

ZBrush 2026 notes

• Knife (2021.7 to 2022) with Split To Parts (2024) replaces most Slice and Trim routines; Knife cannot cut holes.
• ZModeler 2026.0 creases at creation (Insert EdgeLoop, Inset); 2026.2.1 adds Bevel All, Outer or Inner Edges and fixes the Extrude-instead-of-QMesh default.
• Substance Bridge (2026.2.0): Low & High, Auto-Bake, Send PolyPaint; Force UV Auto-Unwrap is global; each send makes a new Painter project.
• 2026.2.1 fixes Live Boolean rendering and an Apply crash. ZRepeat It is not shipped: loop SubTools in Python.
• Blocking notes (2026.2.1 UI strings): coplanar Make Boolean Mesh; floor Elv on Mirror And Weld; n-gons on import; DynaMesh with levels; the Check Mesh Integrity result [verify]; the Create InsertMesh Append-or-New prompt when the current brush is already an insert brush; the shipped Create Instance Subtool macro ends on a note.
• Prefixed labels: s.SmoothSubdiv, P.Panel Loops, a.Repeat, m.Width; sections of Tool > Geometry add no path level. Cmd+W quits ZBrush on macOS; Control+W groups.

References

• references/expert-notes.md: principles by expert, timestamps, deciding conditions; load when planning.
• references/procedures.md: full bridge procedures; load before writing code.
• references/critique.md: the rubric; load at every gate.
• references/gui-paths.md: palettes, hotkeys, brushes; load when a step is GUI only.
• references/sources.md: every source, credential, URL and timestamp.