What if your entire CAD environment was one .htm file you could double-click, drop on a USB drive, or host on a static server — no install, no cloud account, no subscription?
That's NASSCAD. And version 4.2 is a serious piece of engineering.

TL;DR — Full Boolean CSG, 14 watertight primitives, non-destructive history tree, BVH raycasting, a 2 GB geometry arena with mark-and-sweep GC, STL / OBJ / 3MF import-export, M2–M20 fastener library, a JS scripting console. Zero runtime CDN fetches. Works completely offline. Free for non-commercial use (CC BY-NC 4.0).

The premise
Most browser-based CAD tools lean on CDNs, backends, or cloud rendering pipelines. NASSCAD goes the opposite direction: every dependency — Three.js r128, the Manifold WASM CSG engine, fonts, all geometry modules — is either bundled inline or base64-encoded and decoded at runtime via atob(). The manifold.wasm binary lives inside the HTML itself, patched to a self-contained IIFE so it works over file:// with no server.
This is not a toy viewer. It's a full parametric modeler with Boolean operations, a construction tree, undo/redo, multi-format export, scripting, and a 2 GB memory arena.

Core architecture
ModuleRoleThree.js r128WebGL rendering, custom OrbitControls with spherical damping, dual resolution (64 segs display / 128 export)Manifold WASMC++ CSG engine in a Web Worker. N-ary union in a single call. Epsilon vertex merge before handoffGeometryPool512 MB–2 GB binary arena. Bump allocator + free-list reuse + mark-and-sweep GC + XOR checksumBVH RaycasterAABB world-space cache per mesh. Pre-filter before triangle traversal. Fast at 10M+ verticesIndexedDBNamed project persistence, quota display, restore on reload. CSG tree serialized with each saveNassScriptFull JS console with direct access to the NASSCAD internal API. Ctrl+Enter to run, history navigation

The CSG engine — how it actually works
Boolean operations go through a carefully layered pipeline:

Auto hole detection — mix a solid and a hole object in a selection, NASSCAD forces subtract automatically. No manual mode switching needed.
N-ary union — one single Manifold WASM call for N objects, not an O(n²) pairwise loop.
Vertex merge — epsilon 1e-5 quantization before geometry is sent to Manifold. Prevents degenerate triangles from sneaking through.
Post-process pipeline — BFS island normal smoothing (Blender algorithm, crease 30°), area-weighted center-of-gravity recentering, immediate re-render.
Async yield — geometry preparation yields every 10 objects via setTimeout(0). The watchdog timer fires between heavy phases; the UI never hard-freezes.

14 watertight primitives
Every generator uses a shared V() vertex pool (a Map keyed at PREC=1e5) to deduplicate coincident vertices at construction time. The output is an indexed, fully closed mesh that Manifold accepts without repair:

Cylind.Gen — truncated cylinder, double chamfer or round, top and bottom independently configurable, N facets
Cubic.Gen — chamfered/rounded cube, spherical slerp per edge, 1–24 segments
Tore.Gen — ultra-HD torus, periodic topology (i+1)%N · (j+1)%M, zero seam
Pipe.Gen — hollow bent pipe via Bishop-frame parallel transport (zero section twist), outer + inner wall + sealed caps
Gear.Gen — ISO 20° involute gears (spur, helical, herringbone), V-groove pulleys, timing belt pulleys
Standard cube, sphere, cylinder, cone, 3D text (Helvetiker, configurable extrusion + bevel)
M2–M20 fastener library (NUTS_AND_BOLTS.js, CC BY-NC 4.0)

Non-destructive CSG tree
Every Boolean operation records a construction tree snapshot: Union(A, Subtract(B, C))… — recursively, N levels deep. What this enables:

Modify source objects, hit Re-run — NASSCAD reconstructs from the snapshot and re-executes the full CSG chain. No manual redo.
The tree survives Save/Load (serialized into the .json project file via IndexedDB) and Undo/Redo (included in every scene snapshot).
View the tree at any time: Union(A, Subtract(B, C)) displayed recursively in the properties panel.

Performance envelope
ScopeThresholdStatusThree.js rendering< 3M vertices, < 500 objects✅ smoothThree.js rendering3–8M vertices⚠️ fps dropManifold CSG< 10k triangles/object✅ < 1 secManifold CSG10k–50k triangles⚠️ 1–10 secManifold CSG> 50k triangles🔴 risk freezeGeometryPool< 150 complex objects✅ safeGeometryPool> 300 objects or massive CSG🔴 red MEM gauge

Practical tip: for thread-heavy assemblies, place objects without CSG and let the slicer (Cura, PrusaSlicer, Bambu Studio) handle final assembly. STL export at 128 segments is more than sufficient for FDM at 0.4 mm nozzle resolution.

Export / Import
FormatNotesSTL BinaryNative slicer format, Z-up, 4–5× smaller than ASCII. Quality: 128 / 256 / 512 segmentsSTL ASCIILegacy tool compatibilityOBJWavefront with vn normals, compatible with Blender and FreeCAD3MFNative Bambu Studio / PrusaSlicer / Cura, per-object colors, multi-object, clean ZIPImport STL/OBJ/3MFAuto centering, placed on floor grid, Y↔Z axis conversion, per-object colors on 3MF

Why it matters
The dominant CAD platforms are locked into desktop installs, subscription models, or cloud dependencies. NASSCAD makes a different bet: if you can fit a serious CSG modeler, a watertight primitive library, a construction history, and a 2 GB memory arena into a single HTML file that opens offline — then distribution, maintenance, and access cost approach zero.
It's a maker's tool built by a maker who uses it in the field. The design decisions (offline-first, file-portable, no CDN) aren't theoretical — they come from the friction of working in environments where internet access and software licenses aren't guaranteed.

Authors
Nasser — Architect & Field Tester
CLIT · Electronics Technician · 3D Maker, France
Vision, direction, critical bug identification (CSG sizing, manifold edge cases, worker stability), quality standards, technology pivots.
Claude Sonnet 4.6 — Developer
Artificial Intelligence · Anthropic
Web Worker Manifold WASM · Watertight primitives · Manifold geometries verified edge by edge · Surgical patches · Systematic node --check.

Try it → nasscad.com — open it, no install, no account. Works offline. Free for non-commercial use under CC BY-NC 4.0.