kernelcad-fields

kernelCAD — signed-distance fields

Compose signed-distance fields (sdf.sphere/.box/.cylinder/.torus), blend them smoothly with sdf.smoothBlend, then call sdf.materialize(field, { resolution }) to obtain a standard Shape that flows through booleans / fillets / exports.

const a = sdf.box([60, 40, 6]);          // base plate, axis-aligned, centred at origin
const b = sdf.cylinder(8, 30);           // pin, axis +Z, centred at origin
const field = sdf.smoothBlend(a, b, 3);  // 3 mm smooth fillet at the junction
return sdf.materialize(field, { resolution: 30 });

sdf primitive math (mm; centred at origin in local frame)

Field	Returns
sdf.sphere(r)	SdfField (kind 'sphere')
sdf.box([sx, sy, sz])	SdfField (kind 'box', axis-aligned, centred)
sdf.cylinder(r, h)	SdfField (kind 'cylinder', axis +Z, centred)
sdf.torus(R, r)	SdfField (kind 'torus', ring axis +Z, centred)
sdf.smoothBlend(a, b, k)	SdfField (kind 'smoothBlend', polynomial smin with blend radius k mm)
sdf.materialize(field, { resolution? })	Shape (kind sdfMaterialize; default resolution 30, clamped to [10, 200])
sdf.bind(name, field)	binds a field on the session so evaluate_sdf can sample it later (side effect; returns void)

Composition rules (slice 1)

• No field.translate(...). Slice-1 primitives live in their local frame. To position the result, compose primitives whose origins align (e.g. two coaxial spheres), call sdf.materialize, then translate the resulting Shape (.translate(x, y, z)).
• smoothBlend is union-only. Smooth-intersect / smooth-difference are deferred to slice 2+.
• materialize is synchronous. It runs marching-cubes on the host (Node + browser) and synchronously sews via OCCT WASM. No async surface.

Resulting Shape limitations

• The output is polyhedral — thousands of triangular planar faces, not analytic surfaces. Canonical face refs ('top', 'bottom', ...) do not apply (sphere / box face semantics are lost at materialize).
• fillet({ face: 'top' })-style canonical face calls return feature.face-ref.not-applicable; use inline FaceQuery / EdgeQuery if edge-feature scoping is needed.
• Downstream fillet / chamfer on materialized SDF edges is supported in principle but quality is poor and OOM risk is real at high resolution; surface as feature.kernel-failed.
• Booleans (union / subtract / intersect) do work — standard OCCT BREP booleans operate on the polyhedral solid.