feat: add wireframe density controls for flat and curved surfaces

[devaraj3]

What changed

Wireframe mode has been fundamentally reworked. Previously, toggling Wireframe rendered every triangle edge from the mesh tessellation (THREE.WireframeGeometry) as opaque black lines on an opaque solid — an unreadable dense tangle, unrelated to the model's actual geometric edges.

Final architecture:

• Wireframe ON now makes the solid body semi-transparent, with softened (reduced opacity, dark grey rather than pure black) line overlays visible through it
• Edges are classified as flat (near-0° between adjacent triangles — tessellation artifacts with no real shape information) or curved (genuine angle between adjacent triangles — holes, fillets, cylindrical surfaces)
• Flat edges: thinned via spatial/voxel-grid deduplication (one segment kept per 3D grid cell) — produces clean, evenly-distributed crisscross texture without the maze/parallel-only artifacts of earlier attempts
• Curved edges: connected chains are traced first (following shared vertices around a hole rim, fillet, etc.), then thinned along the chain's path order — this keeps loops looking like loops (webs/polygons) instead of fragmenting into disconnected dashes
• Both densities were tunable via sliders during development; final values are now locked in as defaults (Flat Surface Density: 25%, Curved Surface Detail: 65%) and the sliders are hidden from the UI (gated behind SHOW_WIREFRAME_DENSITY_CONTROLS = false, not deleted — a one-line flip re-exposes them later if needed)
• The always-on "feature edge" system (clean part-boundary lines visible regardless of the Wireframe toggle) is completely untouched and independent throughout — this was mistakenly conflated with Wireframe mode in one intermediate attempt, which was identified and reverted

Why

This went through many iterations before landing here, worth summarizing for future reference:

• Root cause of the original density bug: a skip-condition meant to avoid double-rendering checked a flag that was never actually set on the object being checked, so the dense fallback ran unconditionally on every mesh
• Early fixes attempted depthTest/polygonOffset changes to solve back-face bleed-through — these caused GPU-specific regressions (worked in headless testing, failed on real hardware) and were reverted
• Pure angle-threshold filtering (EdgesGeometry alone) was tried at multiple thresholds — always failed one of two ways: too high a threshold destroyed genuine curve detail on small features (holes rendering as bare rings), too low a threshold removed 100% of flat-face diagonals by mathematical necessity, leaving only parallel/circumferential lines
• Pure spatial thinning (no connectivity awareness) handled flat faces well but fragmented curved loops into disconnected dashes
• SimplifyModifier (mesh simplification) produced good curved-surface results but was too slow for live interaction and gave uncoordinated results on flat areas
• The working solution required treating flat and curved geometry as genuinely different problems, each solved with the technique that worked for that specific case, rather than one universal method

Validation

• Flat faces show genuine crisscross/zigzag texture — confirmed visually across multiple rounds, not parallel-lines-only, not a dense tangle
• Counterbore, countersink, and hole boundaries show connected web/polygon structure — confirmed visually, not dashed/fragmented
• Both density values locked to their approved defaults (25% / 65%), sliders hidden, sidebar layout confirmed clean with no gaps
• Always-on feature edges confirmed unaffected and independent of the Wireframe toggle
• Wireframe toggle on/off repeatedly — confirmed stable
• npm run build
• npm run lint
• npm run typecheck
• Full regression matrix (STEP single/multi-part, IGES, STL, OBJ, assembly flat/parts mode) — re-confirm once more on this exact final state before merging, since it was last verified a few iterations ago

Notes

• The two density values are stored as real, working sliders internally — just hidden. If a future need arises (e.g. per-file-type tuning, or exposing to advanced users), re-enabling is a one-line change, not a rebuild
• No changes to picking/raycasting, measurement, or any other viewer feature — this was scoped entirely to wireframe rendering

[vercel]

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Project	Deployment	Actions	Updated (UTC)
cad-viewer	Ready	Preview	Aug 7, 2026 4:40am