marvin-turnstone/skills/3d-modeling-openscad/SKILL.md

name, description, license, compatibility, metadata

name	description	license	compatibility	metadata
3d-modeling-openscad	Generate parametric 3D models using OpenSCAD script	WTFPL	opencode	audience workflow makers, engineers, designers 3d-modeling

What I do

• Write .scad files using OpenSCAD syntax (primitives, transformations, CSG).
• Create parametric models using modules, functions, and variables.
• Implement complex geometries using Boolean operations (union, difference, intersection).
• Apply modifiers like $fn for smoothness or center for alignment.
• Create scripts for procedural 3D design.
• Execute a Visual Verification Loop:
  • Render .scad to .png using the OpenSCAD CLI.
  • Use the read tool to inspect the rendered image.
  • Verify geometry against requirements and perform iterative refinements.

When to use me

Use this when you need to create a 3D printable model through code. Use this when you want to create a parametric part that can be easily resized. Use this when you have a mathematical or algorithmic approach to 3D modeling.

Best Practices

• Ask for details: Use the questions tool to ask for clarifying details.
  • For example: What aspects of the model should be parameterized?

Boolean subtractions

Avoid 3D boolean subtractions. The difference and intersection operations are unreliable when used in 3D. Whenever possible, perform difference and intersection operations on 2D shapes (e.g., circle, square) before using linear_extrude to create 3D volumes. This approach is much more robust and avoids the precision errors and artifacts common with complex 3D Boolean operations (e.g., when creating a tube or a hollow cylinder).

Example: Creating a Tube:

inner_radius = 5;
outer_radius = 7;
height = 10;

// This is the CORRECT way to create a tube:
linear_extrude(height)
difference() {
    circle(r = outer_radius);
    circle(r = inner_radius);
};

// WRONG way to create a tube, don't do this!!! `difference` on 3d objects should be avoided!
difference() {
    cylinder(h = height, r = outer_radius);
    cylinder(h = height, r = inner_radius);
};

Verification Workflow

To ensure the generated .scad file is valid and matches the design intent, run:

openscad <file_name>.scad -o <file_name>.render.png

Purpose:

1. Syntax Check: If the command fails, the script contains errors that must be fixed.
2. Visual Validation: Use the read tool on the resulting .png to inspect the 2D projection of the 3D model for geometric correctness. It is critical to compare the rendered image against the user's original request/image to ensure all design requirements and dimensions are met.