openscad-generator

name	openscad-generator
description	Generates parameterized 3D models using Python templates and OpenSCAD, and compiles them to STL format via a Makefile. Invoke when generating custom STLs.

OpenSCAD STL Generator

This skill provides a scalable methodology for generating parametric 3D models (STL files) using Python, OpenSCAD, and Make.

When to Use

Invoke this skill when you need to programmatically generate multiple variations of a 3D model, create a catalog of STLs, or automate the conversion of parametric templates into 3D printable files.

Architecture

1. Python Script (generate_catalog.py): Acts as the template engine. It defines a base OpenSCAD (.scad) template with placeholders (e.g., {width}, {shape}) and loops over combinations of parameters to generate individual .scad files.
2. OpenSCAD CLI: Used as the compiler to render .scad files into binary .stl files.
3. Makefile: Orchestrates the build process, ensuring only modified .scad files are recompiled, and handles the discovery of the openscad executable across platforms.

Step-by-Step Implementation

1. The Python Generator

Create a Python script that writes .scad files. Use Python's string formatting to inject parameters into an OpenSCAD template.

Important: Because OpenSCAD uses curly braces {} for blocks, you must double them ({{ and }}) in the Python template string so they aren't interpreted as format placeholders.

import os

SCAD_TEMPLATE = """// Parametric Model
module item(w, l) {{
    cube([w, l, 10]);
}}

item({width}, {length});
"""

def generate_catalog():
    os.makedirs("scad_models", exist_ok=True)
    
    # Define combinations
    variants = [
        (10, 20), 
        (15, 30)
    ]
    
    for w, l in variants:
        filename = f"scad_models/item_{w}x{l}.scad"
        content = SCAD_TEMPLATE.format(width=w, length=l)
        with open(filename, "w") as f:
            f.write(content)
        print(f"Generated {filename}")

if __name__ == "__main__":
    generate_catalog()

2. The Makefile

Use a Makefile to automate the STL compilation. It should intelligently detect the OpenSCAD executable (especially on macOS where it resides in /Applications).

.PHONY: all clean scad stl

# Detect OpenSCAD (handles Linux/macOS paths)
OPENSCAD_CMD := $(shell command -v openscad 2> /dev/null)
ifndef OPENSCAD_CMD
	ifneq ("$(wildcard /Applications/OpenSCAD.app/Contents/MacOS/OpenSCAD)","")
		OPENSCAD_CMD := /Applications/OpenSCAD.app/Contents/MacOS/OpenSCAD
	endif
endif

SCAD_FILES := $(wildcard scad_models/*.scad)
STL_FILES := $(patsubst scad_models/%.scad,stl_models/%.stl,$(SCAD_FILES))

all: stl

scad:
	python3 generate_catalog.py

stl: scad $(STL_FILES)

stl_models/%.stl: scad_models/%.scad
	@mkdir -p stl_models
	@if [ -z "$(OPENSCAD_CMD)" ]; then \
		echo "Error: OpenSCAD not found."; \
		exit 1; \
	fi
	$(OPENSCAD_CMD) -o $@ $<
	@echo "Compiled $@"

clean:
	rm -rf scad_models stl_models

3. Execution

1. Generate Templates: Run make scad to execute the Python script and generate the .scad files.
2. Compile to STL: Run make stl (or just make) to compile the .scad files into .stl files.
3. Clean Build: Run make clean to wipe generated directories.

Best Practices

• Separation of Concerns: Keep the geometric logic entirely within OpenSCAD modules and handle the configuration/catalog loop exclusively in Python.
• Directory Structure: Always separate .scad files into scad_models/ and .stl files into stl_models/ to keep the repository clean.
• Parametric OpenSCAD Code: Ensure OpenSCAD scripts are heavily parameterized so the Python script only needs to inject top-level variables.