37 R11: knife polylines, live symmetry, Smart unwrap core half (1.28)

[AlexZ005]

Roadmap 37 R11 (release 1.28): knife polyline cuts, live symmetry, and the core half of the xatlas Smart unwrap module (the module itself is in theprototype-app/modules on branch feat/37-mesh).

What

• Knife polylines: Shift/Ctrl+click (or the touch Multi-select toggle) places a corner. A plain click ends the cut, Enter ends it at the last corner, Backspace takes a corner back, and Esc drops the cut. While a cut is pending, Tool options shows the point count with Back/Cut buttons for touch.
  • Corners that land on the mesh become real vertices. Each one is first snapped to the corner (6 px) or edge (3 px) of the face under it.
  • The whole polyline is one undo entry and one broadcast.
  • Behaviour change: a two-click cut that ends inside the mesh now ends at the clicked point instead of fanning to the triangle's far corner.
• Live symmetry (toolbox Symmetry › "live symmetry"; local, not saved): every edit is mirrored across the axis, from the side the edit changed. Vertex drags move each vertex's mirror twin live, and a vertex on the plane stays on the plane.
  • It hooks the operator boundary, not the commit path. One-shot ops record through recordOp, which mirrors on a microtask and rewrites that same entry, so the op and its mirror are one undo step. The adjust engine mirrors its pure result. Vertex-mode ops pass op=true to commitMeshGeoTriple/Snapshot.
  • Undo, redo, Cancel and peers' edits are applied exactly as made. mirrorTrisCore is the pure half it shares with one-shot Symmetrize.
• UV editor: the Unwrap menus re-read the backend registry each time they open, so a module installed while the editor is open (Smart unwrap) shows up without reopening it.

Proof

• Unit tests:

  • meshKnife: 11/11. Without corner insertion, 4 fail.
  • meshSymmetryLive: 8/8. With a fixed side instead of the edited side, the edit is discarded.
  • Full vitest: 1561/1561.

• svelte-check: 318/47, the same as the baseline. Build passes.

• New and changed e2e suites:

  Suite	Result	What it covers
  mesh-symmetry-live	34/0, two peers	one-shot ops, adjust-engine scrub and settle, knife, vertex twins and plane pinning, one undo entry, undo/redo and peer edits not mirrored
  mesh-knife	41/0, two peers	real Shift+clicks, Backspace, Enter, the Cut button, corners land as vertices, watertight, one undo
  uv-smart-unwrap	19/0, two peers	installs the real zip; on a box and a sphere, UVs stay in 0..1 with no degenerate triangles and no overlapping islands, one undo step, and the peer gets the same mapping

• Standing mesh battery: all 19 suites green, plus mesh-symmetrize 16/0 and uv-unwrap-module 12/0.

  • mesh-advanced-ops failed 9 checks once, all in its separate-to-object section. It was 85/0 on 1.25.0 and 85/0 twice in a row on this branch. This lane doesn't touch separate-to-object.

• Bug found by the run: Backspace never reached a pending cut. The shortcut registry's viewport Backspace row calls preventDefault before its no-op action, so the knife key handler no longer defers to defaultPrevented.

• Screenshots: /home/deck/.code/lanes-30/after-37/37-mesh/05-08*.png.

Owed on a device

• Knife polyline feel, including the snap radii.
• Live symmetry from VR (there is no VR toggle).
• Smart unwrap speed on a Quest: about 1–1.5 s for 10k triangles on the main thread.

Decided forks: QUESTIONS-37-mesh.md. Docs fragment: lanes-30/after-37/37-mesh/docs-fragment.md.

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