Scenario Blender Hard Surface

Blender hard surface

Expert hard surface is controlled light on edges: every edge catches a highlight from a bevel or a support loop, flat faces read perfectly flat, and cuts stay editable until the design is settled. The experts disagree on method (n-gons and booleans vs quad cages and subdivision), not on the checks: order of operations, cutter hygiene, planar faces, a shiny matcap orbit. The agent builds the stack with the toolkit and lets the measurable gates find what a human finds by orbiting. 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-blender-expert (execution channel, review loop, 5.2 API changes). Toolkit: scripts/bx_hardsurface.py (import sys; sys.path.append("<skills>/scenario-blender-hard-surface/scripts"); import bx_hardsurface as HS), world-space meters, stock Blender only.

Stance (the expert delta)

• Cut first, bevel after, normals last. Booleans above the angle-limited micro bevel, Weighted Normal at the very bottom, a late Mirror above it (Ryuu [00:26:26], [00:28:37]; du Mont [00:19:46]). In 5.2 a pinned modifier keeps its relative order inside the pinned group and new modifiers land above it, so pin bottom-up: HS.order_stack does it and HS.add_boolean always lands above the tail (verified).
• Two bevels, two jobs (du Mont [00:12:25] to [00:15:15]): a weight-limited design bevel (8 to 12 segments) on chosen silhouette edges before the cuts, and an angle-limited micro bevel (30 degrees, Harden Normals, Miter Outer Arc) after every cut, because no real edge is perfectly sharp (Gambrell, du Mont, Ryuu).
• A bevel that shrinks after a boolean is geometry, not a setting (du Mont [00:20:18], [00:30:20]). Move the cutter well away from target edges or make it exactly coincident; keep Clamp Overlap on. Clamp Overlap limits the bevel over the whole object: a slot running 0.7 degrees off a facet edge (clamp ratio 3.8) wiped out the 3 mm bevel on a port elsewhere on the part [verified in 5.2.1]. HS.clamp_culprits names the cut.
• Every wall, step, gap and rounding facet must be wider than 2x the micro bevel width [added, verified]: a 1 mm pocket floor, a 1.5 mm wall, a 2 mm groove with 1.5 mm bevels (a 3.1 mm one was clean) and a slot rounded in 30-degree facets all clamped the whole object's bevel.
• If Harden Normals or Weighted Normal changes nothing, the face is not flat (Gambrell [00:01:06]). Flatten it; more normal modifiers will not help.
• Pick the school by the part, not by taste. Planar machined parts with many cuts: n-gons + booleans + bevel + custom normals, about a quarter of the time and stays editable (Gambrell [00:18:01]). Continuous curvature, non-uniform roundness, a sculpt or bake high: quad cage + subdivision (rileyb3d, PzThree). Sharpen subD edges with support loops, not creases: 36,800 vs 3,600 triangles at equal quality (Lampel [00:05:28]).
• EXACT is the solver. Gambrell's 2021 "switch to Fast" predates 5.x: Float left 16 non-manifold edges on a coplanar cutter where Exact and Manifold were clean [verified]. When Exact misbehaves the operand is broken (Ryuu [00:15:13]): an open cutter gave Exact 19 non-manifold edges and Manifold silently skipped the cut [verified].
• Judge in a shiny matcap and close up on every cut (Gambrell [00:00:33], rileyb3d [00:06:32]). Whole-object sheets hide smears and shrunken bevels.

Establish first

Workflow

1. Blockout at real size. Primitives or bmesh, then HS.apply_scale(ob) (keeps children in place, flips winding on negative scale). Check proportions against a human-scale box through a long lens (du Mont [00:10:01]). GATE: scale is 1 on every object with a bevel, solidify or array; silhouette sheet reads (bx_review.review(..., modes=("silhouette",))).
2. Pick the school and build the base stack.
   • A: design edges with HS.find_edges(ob, min_angle=80, inside=...) + HS.set_edge_attr(ob, edges, 1.0), then HS.hard_surface_stack(ob, micro_width=..., design_width=...).
   • B: quad cage in bmesh (few control points, square quads, rileyb3d / PzThree), then HS.subd_stack(ob, support_width=...) (Bevel Weight, even segments, profile 1.0, Subdivision with UV Smooth Keep Corners) or explicit HS.support_loops. GATE: HS.stack_problems(ob) == []; A has custom normals on the evaluated mesh.
3. Cut (School A). HS.make_cutter(target, "BOX"|"CYLINDER"|"SLOT", size, location, ...) builds a cutter that meets the checklist (scale 1, smooth, Cutters collection only, wire, hidden from render, parented, EXACT, wired above the tail). HS.as_cutter for custom shapes, HS.slice_boolean for Slice. Rules: extend past every surface entered; keep cutter edges far from target edges or exactly on them; offset a round cutter by half a segment against a target with the same count (same phase gave 10 non-manifold edges and streaks [verified]; make_cutter default); round cutter corners in facets well under the bevel angle (4+ segments per 90 degrees). GATE after each cut: HS.cutter_report(c, target) clean, HS.clamp_probe(target)["ratio"] < 0.1, a HS.closeup of the cut looked at.
4. Design pass. Cluster details, leave calm areas, align with neighboring features (Ryuu [00:28:37], Gambrell [00:34:15]); hide perfect intersections behind a collar (du Mont [00:39:36]); union parts that must share a bevel (Gambrell [00:18:57]). GATE: a review sheet shows intent, not noise.
5. Shading pass. r = HS.shading_audit(ob); HS.verdict(r), then HS.review([ob], out, modes=("matcap","reflect","hsgrey","wire")) and closeups. Triage with references/critique.md: smear on flat faces, non-planar faces, cuts on curvature (render first: Harden + WN already shaded 24/48-segment cylinder cuts cleanly; on a sphere HS.transfer_normals cut the normal error p95 from 2.79 to 0.34 degrees [verified]), mirror seam (HS.mirror_seam_fix). GATE: verdict empty or every remaining line explained, and the closeups agree.
6. School B detail and pinch check. Even bevel segments, profile 1.0, Keep Corners (Lampel [00:11:15]); brace both sides of a ridge equally (rileyb3d [00:11:08]); outset a border ring around inset circles (PzThree [00:42:25]); turn subdivision off to debug a cage artifact (Gambrell [00:14:44]). GATE: r["subd_cage"] quads near 100%, no long rectangles on a cage that will be sculpted, shiny-matcap closeups free of pinches.
7. Game or export. Mid-poly: g, tris = HS.game_version(ob, micro_segments=1) (Triangulate with keep custom normals after WN; stays in place because it shares the cutters); glTF kept the custom normals 100% [verified]. Baked asset: the low poly and bake go to scenario-blender-retopology and scenario-blender-uv-baking. Rig or export: HS.collapse(ob) on a copy (du Mont [01:07:29]). GATE: tri count within budget, triangles only, matcap closeup of the game copy.
8. Deliver renders, the verdict, tris per object, and what was not verified.