rendr

type words → get a 3D model ready to print

rendr is a little desktop app that turns plain English into manufacturable 3D models. describe what you want, watch it generate OpenSCAD code, compile to a mesh right in your browser, and refine it until it's ready to send to your printer.

this is a personal project — rough edges and all.

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what it does

"a threaded bolt with a hex head"
        ↓
  OpenSCAD code
        ↓
  3D mesh in browser
        ↓
  print analysis + STL download

generation pipeline — 7-stage LangGraph state machine. starts with a TF-IDF similarity search over ~7k OpenSCAD models; direct matches skip the LLM entirely. otherwise it plans → generates → fixes syntax → validates → reviews → refines.

3D viewer — orbit controls, wireframe/solid modes, 9 color presets, adjustable material properties, STL download.

mesh analysis — watertight check, genus, Euler characteristic, surface area, volume, center of mass, and a 5-point print readiness checklist with weight/time/cost estimates for 6 materials.

parametric controls — auto-detected sliders and toggles for any parameter in the code. tweak values and the model recompiles live.

print simulation — layer-by-layer build animation with playback controls.

code editor — CodeMirror 6 with syntax highlighting. edit the code directly and the viewer updates.

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stack

desktop shell	Electron 33
frontend	React 18 · TypeScript · Tailwind CSS
3D	Three.js via React Three Fiber
editor	CodeMirror 6
3D compilation	OpenSCAD WASM (Web Worker, no install needed)
backend	FastAPI · Python 3.11+
db	SQLite via aiosqlite
pipeline	LangGraph
review agent	Railtracks
LLMs	Claude Sonnet 4 (generation) · Claude Haiku 4.5 (fast steps)
retrieval	TF-IDF + cosine similarity · 7,378 Thingiverse models

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getting started

you'll need

• Node.js >= 18
• Python >= 3.11
• An API key — Anthropic (recommended), OpenAI, or a local Ollama instance
• OpenSCAD (optional) — only for server-side PNG export. the 3D viewer works without it via WASM

1 · clone

git clone https://github.com/Krishpraj/rendr.git
cd rendr

2 · backend

cd rendr-api
python -m venv .venv

# windows
.venv\Scripts\activate
# mac / linux
source .venv/bin/activate

pip install -e .

create rendr-api/.env and drop in your key:

ANTHROPIC_API_KEY=sk-ant-...

3 · frontend

cd rendr-app
npm install

4 · run

windows (powershell):

.\start-dev.ps1

everyone else (two terminals):

# terminal 1
cd rendr-api && uvicorn rendr_api.main:app --reload

# terminal 2
cd rendr-app && npm run dev

API runs at http://localhost:8000. Electron connects automatically.

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configuration

all options go in rendr-api/.env

variable	default	what it does
LLM_PROVIDER	anthropic	anthropic · openai · ollama
LLM_MODEL	claude-sonnet-4-20250514	primary generation model
FAST_PROVIDER	anthropic	provider for lightweight steps
FAST_MODEL	claude-haiku-4-5-20251001	fast model for validation/review
ANTHROPIC_API_KEY	—	required for Anthropic
OPENAI_API_KEY	—	required for OpenAI
OPENAI_API_BASE	—	custom OpenAI-compatible endpoint
OLLAMA_HOST	http://localhost:11434	Ollama server URL
OPENSCAD_PATH	openscad	path to binary (PNG export only)
TEMPERATURE	0.0	LLM temperature
MAX_REFINEMENT_ROUNDS	2	max generate→review iterations
HOST	0.0.0.0	API bind host
PORT	8000	API bind port

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project structure

rendr/
├── rendr-api/                  # FastAPI backend
│   ├── rendr_api/
│   │   ├── main.py             # entry point, CORS, router mounting
│   │   ├── config.py           # pydantic settings from .env
│   │   ├── routers/            # /health /edit /render /projects
│   │   └── services/
│   │       ├── pipeline.py     # LangGraph 7-stage state machine
│   │       ├── review_agent.py # Railtracks agent + tool nodes
│   │       ├── retrieval.py    # TF-IDF search over dataset
│   │       ├── parameters.py   # OpenSCAD parameter extraction
│   │       └── database.py     # SQLite (projects, chat history)
│   └── train-00000-of-00001.parquet   # 7,378 OpenSCAD models
│
└── rendr-app/                  # Electron + React frontend
    └── src/renderer/src/
        ├── components/
        │   ├── chat/           # chat panel + pipeline progress
        │   ├── preview/        # 3D viewer, code editor, STL renderer
        │   ├── workspace/      # analysis, parameters, print sim
        │   └── welcome/        # home screen + project cards
        ├── contexts/           # Project, Chat, MeshAnalytics state
        ├── hooks/              # useEditStream, useRender, useBackendHealth
        ├── lib/                # API client, mesh analytics, WASM bridge
        └── workers/            # OpenSCAD WASM Web Worker

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troubleshooting

status bar says "Offline" backend isn't running — cd rendr-api && uvicorn rendr_api.main:app --reload

stuck on "Building 3D model..." WASM hit an error. open DevTools (Ctrl+Shift+I) and check the console for OpenSCAD output. usually a syntax error in generated code.

PNG export fails needs the OpenSCAD binary installed and in PATH (or set OPENSCAD_PATH). download at openscad.org.

pipeline keeps looping the review agent is rejecting the code. lower MAX_REFINEMENT_ROUNDS in .env, or use "fast" mode in the chat which skips validation and review.

model looks wrong but compiles check the Analysis tab → print readiness. non-watertight meshes or high genus values usually point to geometry issues.

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credits

CADAM — parametric CAD modeling environment that informed rendr's approach to code-driven 3D design

openscad-playground — browser-based OpenSCAD editor that proved client-side compilation was viable and shaped the in-browser rendering architecture

openscad-wasm — OpenSCAD compiled to WebAssembly, the engine that powers rendr's 3D compilation without requiring a local OpenSCAD install

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