negative-support 0.1.0

Negative-space 3D print support generator for STEP and mesh files

negative-support — Negative-Space 3D Print Support Generator

Generates model-conforming support structures for 3D printing. Unlike slicer-generated tree or grid supports, these are negative-space supports — exact shapes created by subtracting the model from a surrounding block, filling internal cavities (overhangs, bridges, holes) with solid mesh that conforms to the model's actual surface contours.

Supports two input modes:

• STEP files (.step/.stp) — uses B-Rep face topology for smart overhang detection. Only faces that actually need support get it.
• Mesh files (.stl/.obj/.ply/.3mf) — generates full-shell supports around the entire model. No overhang detection (no B-Rep topology), so all surfaces get support. Uses more material but works with any mesh format.

The output is a separate STL file that can be imported alongside the model in your slicer.

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Install

Requires Python 3.10+.

pip install negative-support

For STEP file support (B-Rep overhang detection), install the optional dependency:

pip install negative-support[step]

Usage

negative-support model.step                # STEP: overhang detection
negative-support model.stl                 # Mesh: full-shell supports
negative-support model.step -m 0.15 -a 40  # tighter margin + stricter angle
negative-support model.step -e             # also export model as STL
negative-support model.step -q             # quiet mode for scripting

The input format is auto-detected by file extension.

CLI Flags

Flag	Short	Default	Description
input		(required)	Path to input file (STEP/STP or STL/OBJ/PLY/3MF)
--output	-o	<input>_supports.stl	Output STL path
--margin	-m	0.2	Gap between support and model (mm)
--angle	-a	45.0	Overhang angle threshold (STEP only)
--min-volume		1.0	Discard support pieces smaller than this (mm³)
--tolerance		0.01	STL tessellation tolerance (STEP only)
--export-model	-e	off	Also export the STEP model as STL
--quiet	-q	off	Suppress progress display
--debug		off	Print per-face diagnostics (STEP only)

License Commands

negative-support --status                          # show license status
negative-support --buy                             # open purchase page in browser
negative-support --activate ns_live_<your_token>   # activate a license token
negative-support --version                         # show version

Python API

from negative_support import load_step, compute_supports

part, z_offset = load_step("model.step")
supports = compute_supports(part, margin=0.2, angle=45.0)
supports.export("supports.stl")

from negative_support import load_mesh, compute_supports_mesh

mesh, z_offset = load_mesh("model.stl")
supports = compute_supports_mesh(mesh, margin=0.2)
supports.export("supports.stl")

Progress Display

STEP mode:

  ✓ Tessellate          28,912 faces          0.1s
  ✓ Inflate             150,788 faces        22.3s
  ✓ Negative space      702,596 mm³           0.1s
  ✓ Detect overhangs    92 faces              2.4s
  ✓ Extract supports    134 pieces            1.9s
  ✓ Merge               113,754 faces         0.0s

Mesh mode:

  ✓ Inflate             87,980 faces         10.2s
  ✓ Negative space      702,609 mm³           0.1s
  ✓ Split & filter      1 pieces              0.1s
  ✓ Merge               84,924 faces          0.0s

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How It Works

STEP Pipeline (overhang detection)

1. Load STEP — imports the B-Rep model with full parametric face topology
2. Tessellate — converts the parametric model to a triangle mesh
3. Inflate — grows the model mesh outward by the margin using Minkowski sum with a sphere (via manifold3d)
4. Detect overhangs — identifies faces that need support using B-Rep normals and mid-air detection
5. Extract supports — for each overhang face, creates a vertical column and intersects it with the negative space
6. Merge & export — combines all support pieces into a single STL file

Mesh Pipeline (full-shell)

1. Load mesh — imports the triangle mesh directly
2. Inflate — grows the mesh outward by the margin (same Minkowski sum)
3. Negative space — computes the void around the inflated model (bounding box minus inflated mesh)
4. Split & filter — separates into pieces and removes tiny fragments
5. Merge & export — combines all support pieces into a single STL file

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Licensing

Free tier: 3 runs per machine, no account needed. After that, a lifetime license is required ($29, one-time).

• Tracked server-side via machine fingerprint (SHA-256 of hostname + MAC + OS + arch + username)
• Offline fallback: local counter in ~/.negative-support/usage.json
• Token format: ns_live_<32 hex chars>, stored in ~/.negative-support/license.json
• Grace period: 7 days offline after last server validation

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Project Structure

├── pyproject.toml                    # Package metadata (hatchling)
├── src/negative_support/
│   ├── __init__.py                   # Version + public API
│   ├── cli.py                        # Main CLI + compute functions
│   ├── license.py                    # License checking + free tier
│   └── progress.py                   # ProgressDisplay (spinner/bar)
├── server/
│   ├── wrangler.toml                 # Cloudflare Worker config
│   ├── package.json                  # Server dependencies
│   ├── schema.sql                    # D1 database migration
│   ├── src/
│   │   ├── index.ts                  # Worker entry + router
│   │   └── api.ts                    # API route handlers
│   └── web/                          # React SPA (Vite)
│       ├── package.json
│       ├── vite.config.ts
│       └── src/
│           ├── App.tsx               # Router
│           ├── pages/Landing.tsx     # Landing page + pricing
│           ├── pages/Success.tsx     # Post-payment token display
│           └── pages/Docs.tsx        # Usage documentation
├── step_supports.py                  # Backwards-compat wrapper
├── tests/
│   ├── baseline.py                   # Regression test
│   ├── baseline.json                 # Saved snapshot
│   └── baseline_generator.py         # Reference algorithm
└── models/                           # Dev-only test models

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Development

Local setup (Python CLI)

# Create venv with Python 3.10+
python3.13 -m venv .venv
source .venv/bin/activate

# Install in editable mode
pip install -e .              # mesh-only
pip install -e ".[step]"      # mesh + STEP support

# Verify
negative-support --version
negative-support --status

Run tests

source .venv/bin/activate
python tests/baseline.py                # compare against snapshot
python tests/baseline.py --update       # update after intentional changes

Build package

pip install build
python -m build
ls dist/   # negative_support-0.1.0.tar.gz + .whl

Publish to PyPI

pip install twine

# Test PyPI first
twine upload --repository testpypi dist/*

# Production
twine upload dist/*

Local setup (Server)

cd server
npm install
cd web && npm install && cd ..

# Copy env template
cp .dev.vars.example .dev.vars
# Edit .dev.vars with real Stripe keys

Run server locally

# Terminal 1: API server
cd server
npm run migrate:local    # create D1 tables locally
npm run dev              # wrangler dev on :8787

# Terminal 2: React dev server
cd server/web
npm run dev              # vite on :5173, proxies /api to :8787

Deploy server

cd server

# 1. Create D1 database (first time only)
npx wrangler d1 create negative-support-db
# Copy the database_id into wrangler.toml

# 2. Run migration
npm run migrate

# 3. Set secrets
npx wrangler secret put STRIPE_SECRET_KEY
npx wrangler secret put STRIPE_WEBHOOK_SECRET

# 4. Update placeholders in src/api.ts:
#    - PRICE_ID → your Stripe Price ID
#    - SUCCESS_URL / CANCEL_URL → your domain

# 5. Build frontend + deploy worker
npm run deploy

# 6. Set up Stripe webhook in Dashboard:
#    URL: https://<worker>.workers.dev/api/webhook/stripe
#    Events: checkout.session.completed

Server API endpoints

Method	Path	Purpose
POST	/api/free-tier	Track machine runs, return remaining
POST	/api/validate	Check token validity
POST	/api/activate	Bind token to machine (max 3)
POST	/api/webhook/stripe	Stripe payment → generate token
GET	/api/token?session_id=x	Fetch token after payment
POST	/api/checkout	Create Stripe Checkout Session

Server database (D1/SQLite)

• machines: machine_id, runs_used, first_seen, last_seen
• licenses: token, email, plan, stripe_session_id, created_at
• machine_licenses: token, machine_id, activated_at (max 3 per token)

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Limitations

• No tree supports — generates solid block supports, which use more material but conform exactly to the model surface
• Mesh input = full shell — without B-Rep topology, every surface gets support. Use STEP input for smart overhang-only supports.
• Processing time — the Minkowski sum inflation step can take 20-30s on complex models (400+ faces)