ZBrush retopology and export (pipeline sculptor)

Expert level means the sculpt leaves ZBrush as a light, clean exchange mesh at its lowest level, detail kept on a rebuilt subdivision stack or in maps, at real size, every file proved by parsing it. Most of it is deterministic palette work an agent does well; click-by-click topology, modifier clicks and a few dialogs stay with a human or computer-use agent. 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_retopology_export.py (rx) on top of the lead's zb_ops, zb_audit and zb_launch: rx.zcall("func", ...) inside ZBrush, audits on the agent side. Every projection pass is the lead's safe zb_ops.project_all (versioned checkpoint, nets, gate). Not yet run in ZBrush (88 offline tests pass; live tests in references/procedures.md).

Stance (the expert delta)

• Set symmetry on purpose before every ZRemesher run. With symmetry on, ZRemesher remeshes half and mirrors it: a silent Mirror And Weld that ruins posed or asymmetric meshes (Drust, Kjce71jjWJU 00:01:11). rx.zremesh makes symmetric a required argument.
• Give ZRemesher an easy problem. A face that will animate goes in neutral, folds relaxed, the expression sculpted back on the new topology (Pavlovich n5_cZK-9peg 00:01:39). Ears and hands are remeshed alone, open borders polished first (00:44:36). Unintended holes are closed first: they survive and inflate the count (ZRemesher doc).
• ZRemesher is for flow; detail comes back by projection. Aim low (Gaboury: 5k to 18k for an arm, 34D6VljTjBs 00:02:18), then Project All with Dist 0.1, which fixes "90 percent" of artifacts (Drust nxMYYsyJt3o 00:02:19). Only source and target visible, even in Solo (Pavlovich 01:07:26). With Adapt on and Keep Groups, Target 5 gave 8.0k to 9.4k points (frames 00:18:50, 00:22:09); Adapt off hits the count.
• Projection has danger zones: eyes, mouth, armpits, between fingers, crotch; what is left there becomes hard lines in displacement (FlippedNormals Zp07GW3rND0 00:07:43). Mask an eye-interior group grown just past the lid; repair with the morph target or a masked reprojection, never smoothing (00:05:31, 00:06:36).
• Steer with polygroups, borders smoothed first: ZRemesher builds jagged borders into the loops (Pavlovich 00:05:27). Smooth Groups 0 on clean borders, 1 for ragged DynaMesh groups (Drust 8D-xqasgUws 00:02:17). Failed eyelids, mouth corners and nostrils are deleted and rebuilt (Pavlovich 00:21:36); the Retopo brush's "No" answer makes a light ZRemesher mesh editable (Pablo Munoz Gomez, I4nePXDTrhQ 00:06:36).
• The lowest level is the exchange mesh. UVs are made there (Gaboury cemmalvugFk 00:00:51). Maps compare the current level with the top of the same SubTool, never two SubTools (Drust n0qqpwvn-jA 00:01:14); level 1 carries forms, max-1 micro detail only (2zDAtaQqwh8 00:02:53).
• Film displacement is a fixed recipe (FlippedNormals -ThBTEc8L_M): Flip V on ("an absolute must"), Adaptive off (100 UDIMs in about 1 h, not 24 h), DpSubPix 0, 32-bit EXR, 3 Channels off, renderer zero value = Mid (MME doc: Mid 0 for 32-bit; FlippedNormals keep 0.5; record it).
• Exported size = internal extent x Export Scale (Drust n2xPrwI9o1U 00:04:19). Keep XYZ Size between 1 and 4 (Gallagher EXjfH_X2hkM 00:28:23). Export Scale and offsets live per SubTool, so the same values go on every SubTool [added].
• A generated or scanned mesh is a form reference, not topology to repair. DynaMesh early, after thickening thin shells, which DynaMesh's hole fill "shoots straight across" (Drust PrFQXjs_6_w 00:02:53). Rebuild the stack from the cleaned DynaMesh, never the noisy original [added].

Establish first

Input	Changes	Default when the brief is silent
Destinations	mesh type, maps, units, axis	Maya: OBJ level 1 quads in cm + 32-bit EXR displacement, Mid 0.5
Deforms? face, joints	exact loops (human Retopo pass), neutral face	yes for characters; an expression goes back to scenario-zbrush-character-creature (neutral version, or its layer off)
Budget	ZRemesher target, Adapt	rig or film body 15k to 25k quads [added]; animated head 10k to 20k (Retopo doc); game from the brief
Posed or asymmetric	symmetry off	symmetric only if unposed and designed symmetric
Real size	Export Scale	180 cm human (Gallagher's example)
Maps and tiles	MME preset, UDIM plan	one 4096 tile per SubTool; UDIM layouts come from Maya or Blender
Source type	route	levels: a level under 2M; none: DynaMesh copy; AI or scan: cleanup first

Workflow

1. Preflight, checkpoint. rx.zcall("preflight", 180.0); zb_ops.save_ztl. GATE: flags resolved (over 8M vertices, XYZ Size outside 1 to 4, Export Scale 0, duplicate names).
2. ZRemesher input. remesh_input("auto", max_points=2_000_000) duplicates the sculpt and hides the original (the projection source); fill_holes=True adds Close Holes and Fix Mesh when holes are unintended. DynaMesh and Close Holes also shut eye sockets and mouth bags: openings_closed sets the hole gate (0, else the intended openings). GATE: copy under 8M vertices, source intact, face neutral.
3. Guides. Polygroups by buttons (Auto Groups, Groups By Normals, From Polypaint); a mask a human drew becomes a group with support loops through Edgeloop Masked Border (Drust IpTYcGxxsdM 00:05:08); polish_band("groups"). Ears and hands: own SubTools (Groups Split, Split Hidden), polish_band("border"), own runs (hand Adaptive Size about 14: Pavlovich 00:59:42), then merge_down_run(..., weld=True); Freeze Border only where borders must re-weld exactly, after remeshing the whole limb, at a cost to animation (01:03:44). GATE: Polyframe sheet shows closed, smooth rings; no seam loops after the re-join.
4. ZRemesher. zremesh(target_k, symmetric, keep_groups=True, smooth_groups=0) (Half, Same, Double off), then retry(adaptive_size=...) over 0, 5, 21. Keep Groups, Keep Creases, Smooth Groups or a sculpt break the Retry cache. The sweep leaves the LAST variant: pick_retry, retry(**pick["retry"]), confirm_retry. Optional Half pass with Adapt off, or a retopology over the retopology (Drust R2MzFqWMaWY 00:01:44). Poor center line at nape or brow: Alt+ZRemesher, a modifier click press cannot send: ask computer use, compare centre_line_components (Pavlovich 00:48:31). When snap_back is true, project_stack(copy, source, levels=0, checkpoint=ztl) before judging (00:22:05). GATE: in_band; topo_report + retopo_verdict(purpose="rig", expected_holes=...) on a Grp-on QA export; loops follow forms. Failed orifices: the script stops for a human Retopo pass.
5. Rebuild the stack. project_stack(target, source, checkpoint=ztl): two visible, Dist 0.1, level 1 then Divide + Project All per level up to half the source count, a morph target per pass, color last with Colorize on for both SubTools (Drust PrFQXjs_6_w 00:16:35). Danger zones or a film face: order="top_first", stop_after="nets" (divisions, then StoreMT and a layer at the top: FlippedNormals 00:02:13), a human isolates the eye-interior group, protect_isolated(grow=1), project_levels(..., nets_done=True). GATE: projection_from_stack (level 1 unchanged, bbox 0.5 percent, volume 2 percent [added]); same-view sheet plus danger-zone close-ups per level. Busted areas: zb_ops.morph_repair; a target inside the source: masked Inflate, or ProjectionShell with Inner and Dist 1 (Gaboury pQbPtH0p5Bg 00:02:30). Then drop_morph_target(): bakes refuse a stored morph target, a possible map base (Drust 2zDAtaQqwh8 00:01:44) [verify].
6. UVs at level 1 (they carry through the levels, Gaboury cemmalvugFk 00:03:30). Quick: zb_ops.uv_unwrap("native"). Explicit seams: unwrap_creases() (Pavlovich cvqoVUX5aBw). Painter islands: uvmaster_roundtrip(). Eyes get their own simple UVs. GATE: uv_verdict on the Txr export; seams hidden, face uncut.
7. Maps. mme_create_all(dir, name, settings="arnold") or bake_normal_map / bake_displacement_map. GATE: map_verdict per file (size, bits, flat at Mid, normal flat at 128/128/255: Polycount); orientation calibrated once per build (live_rx_04 fixture).
8. Scale, names, export. set_export_scale(180, axis=1) (every SubTool); set_export_switches(quads=True, uvs=True, groups=False); export_subtools(dir, level="lowest"). FBX: ZScript could not suppress its options window, Python is unverified (Maxon forum), AppleScript System Events clicks ZBrush dialogs on this Mac [verify for it]; default: OBJ, converted by scenario-maya-expert or scenario-blender-expert. GATE: obj_header reads the Export Scale back from #Auto scale (written by 2026.2.1, lead v03 export); scale_report passes (1 percent, feet at 0, centered).
9. Handoff. handoff_report(json, ...): meshes, maps, unit, axis, Mid and scale, normal convention, audits, sheets, not-verified list.

Generated or scanned mesh (Z6)

1. GLB from scenario-3d: glb_to_obj, triage_ai_mesh(obj, expected_parts), then orient_for_import: it rotates only a Z-up hint, centers only an off-center mesh (glTF is Y-up) and names the file to import.
2. import_mesh (Weld; Tri2Quad rebuilds quads from AI triangles [verify range]); raw ZTL; duplicate_keep(): the copy is the form and color source, tracked by name (index_of), since splits and merges renumber SubTools.
3. fix_mesh; split_parts, hide_small_parts(protect_names=[raw]). Fused parts of different colors: color_to_groups, Groups Split [added]; else scenario-3d segmentation or human SliceCurve cuts.
4. close_holes per part. Swiss cheese after DynaMesh means too thin: thicken first.
5. merge_down_run the parts of one body inside the Tool (Drust 00:09:27). dynamesh_keep(res, keep="groups"): with polypaint on, DynaMesh keeps paint INSTEAD of polygroups (DynaMesh doc; general rule: scenario-zbrush-sculpting). Blur 0, Project off. Residual holes: hole_plugs(obj) on an export, plug_hole(center, diameter), merge_into(body, [plug]), re-DynaMesh (Drust PrFQXjs_6_w 00:07:16). Polish; Mirror And Weld if symmetric. Local rebuilds: Sculptris Pro (scenario-zbrush-sculpting).
6. GATE: cleanup_verdict(raw, clean) (closed, manifold, shells, bbox 2 percent, roughness at most 0.8x raw [added]); MatCap Gray sheet, Double on, Colorize off for the sheet only (set_display returns the old value).
7. ZRemesher per part (5 to 20 thousand), snap back, project geometry from the cleaned DynaMesh, then color only from the raw copy: project_levels(..., geometry=False, color_last=True) [verify]. Hand to scenario-zbrush-sculpting (big changes at SDiv 1, secondary at 2 to 3).

Numbers

Value	Relative to	Source
ZRemesher target in thousands; 5 gave 4,963	Target Polygons Count	Pablo rArw79xEpvE 00:03:16
Adaptive Size 50 default; 0 even quads, 5 to 21 curvy; hand about 14	density	ZRemesher doc; Pavlovich n5
Color Density 2 = more (pink), 0.25 = fewer (blue), white neutral	polypaint density	Pavlovich n5 01:01:32
XYZ Size 1 to 4; imports normalized to 2	internal size	Gallagher; Drust
Export Scale = target / internal extent (180 / 2 = 90)	units	Drust; Gallagher 00:28:55

Per-target settings

Target	Mesh	Displacement	Normal
Maya + Arnold	OBJ level 1, Qud, Txr, Grp off; cm	32-bit EXR, Mid 0.5 = Scalar Zero Value, Catmull-Clark about 3, Auto Bump	tangent, OpenGL [added]
Unreal, Unity	triangulated, FBX via Maya or Blender; cm, meters [added]	none	engine tangent basis; Unreal DirectX green [added]
Substance Painter	Substance Bridge Low & High, Auto-Bake, Force Auto-Unwrap off	none	baked by Painter
Blender	OBJ; meters	32-bit EXR, Midlevel = Mid [added]	OpenGL; game bakes with scenario-blender-uv-baking

Redshift, vector displacement and full rows: rx.RENDERERS, references/procedures.md.

Quality gates

• Code, on every exported file: topo_report, projection_verdict, uv_report, scale_report, map_verdict, names_report, cleanup_verdict.
• Visual (zb_review.review sheets): Polyframe front, side and three-quarter for loops; source and target at one view after projection, plus danger-zone close-ups at every level; MatCap Gray with Double on for cleanup. Judge with references/critique.md.

Common mistakes

Mistake	Looks like	Fix
Symmetry left on	posed limbs come out mirrored	zremesh(symmetric=False)
Remeshing a smiling face	loops follow the smile, not the rig	neutral first, expression back on the new mesh
Retry sweep left as is	kept mesh is not the chosen one	pick_retry, retry back, confirm_retry
Dist too small	holes of detail, speckles	Dist 0.1; engulf the source
Smoothing projection spikes	rogue vertices stay	morph target, masked reprojection
Colorize off on one side	projected color missing	color_last=True turns both on
Morph target left at bake	map against the wrong base [verify]	drop_morph_target()
SDK normal bake on defaults	world-space map	create_normal_map(..., local_coordinates=True)
OBJ Grp on for Maya	mesh split in parts	Grp off (FlippedNormals 00:15:08)
Export Scale on one SubTool only	eyes float off the head	set_export_scale(..., all_subtools=True)
Unify on a character with layers	layers and morphs break	MultiAppend into a scaled tool (Gallagher 00:27:16)
Polypaint on at an AI-mesh DynaMesh	part polygroups gone	dynamesh_keep(keep="groups")
MergeVisible during cleanup	new Merged_ Tool without the color source	merge_down_run in the Tool

Handoffs

• Receives from scenario-zbrush-sculpting, scenario-zbrush-character-creature, scenario-zbrush-stylized, scenario-zbrush-hard-surface: a versioned ZTL with named SubTools, stats() and the last sheet; from scenario-3d: GLB or OBJ.
• Delivers to scenario-maya-retopology-uv and scenario-maya-rigging: level-1 OBJ per SubTool, cm, Y-up, centered, feet at 0, eyes separate; to scenario-maya-lookdev: maps plus handoff_report; to scenario-blender-uv-baking or Substance: low and decimated high with matching names; to scenario-zbrush-paint-render: the stack with UVs; to scenario-zbrush-pose-print: a closed copy.

ZBrush 2026 notes

• Retopo brushes (2026.1); UV Master with Polygroups fixed in 2026.2.0; Substance Bridge (2026.2) labels "Auto-Bake", "Force Auto-Unwrap" [uistr]: Force Auto-Unwrap is global and strips good UVs.
• SDK: press() takes no modifier (Alt-clicks go to computer use); create_normal_map() defaults to world space.
• macOS: Control+W makes a polygroup; Command+W quits ZBrush (version deltas 3.13).
• A partial ZRemesh with Freeze Border deletes the subdivision levels (Drust 0TlG4Ex9lQA 00:02:26): freeze_levels() around it.

References

• references/procedures.md: full bridge procedures (Z4, Z6, maps per target, fixtures), test paths, path evidence. Load before running a stage.
• references/expert-notes.md: judgment by expert with timestamps and the deciding conditions. Load when choosing between routes.
• references/critique.md: the review rubric (loops, projection, UVs, maps, scale, cleanup). Load at every gate.
• references/gui-paths.md: palettes, hotkeys and Retopo brush gestures for a human or computer-use agent.
• references/sources.md: every source with credential, URL and best timestamps.