Add OpenSCAD support for exporting models in STEP format

[t-paul]

Outline

The STEP format is widely used in the industry to transfer CAD data between different systems. Currently OpenSCAD does not support STEP import or export. Adding STEP export would open up a number of new usecases or simplify the workflow as no external conversion tools are needed to convert to STEP. This includes the design of 3D models for other CAD tools, e.g. for KiCAD where STEP models are used to render 3D representations of PCBs. Other use cases are for manufacturing where sometimes only STEP files are accepted as input, e.g. for CNC milling services.

Details

The main focus of this project is to get the ground work done for exporting more detailed models, as opposed to just exporting the fully rendered single mesh which is the normal case right now.

Topics that need to be solved

• Research options of usable libraries
• Investigate what type of STEP files are accepted as input by various tools
• Select library and integrate into OpenSCAD
• Implement base functionality to export single meshes
• Add test cases to verify the new export functionality
• Update build system to include the new library into installers
• Prototype how more advanced models can be exported

Expected Outcome

• OpenSCAD supports exporting single meshes as STEP
• (optional) Understanding/Plan of how to support additional features supported by STEP

Project Properties

Skills

• Programming language is C++
• Understand and use APIs from external libraries
• Integrate new libraries into the build system for the 3 supported platforms
• Add test cases with files using the new features to allow regression testing

Difficulty

Hard

Size

Long (350h)

Additional Information

• Potential mentor(s): Marius Kintel (IRC: kintel), Torsten Paul (IRC: teepee), Ryan Colyer (IRC: InPhase)
• Organization website: https://www.openscad.org/

Known libraries:

• StepCode - http://stepcode.org/ (https://github.com/stepcode/stepcode)
• OpenCASCADE - https://www.opencascade.com/

[arybhatt4533]

Hi @t-paul and OpenSCAD team,

I am very interested in working on the STEP export support project for GSoC 2026. I understand that the primary goal is to move beyond simple mesh exports and establish a foundation for exporting detailed 3D models that are compatible with tools like KiCAD and CNC services.

I have started researching the libraries mentioned:

StepCode: Seems lightweight for basic STEP structures.

OpenCASCADE: Much more powerful but adds significant weight to the build system.

I am particularly interested in the challenge of integrating these into the existing OpenSCAD build pipeline across all three platforms. I am currently setting up the local development environment to explore the current export logic.

Could you please guide me on any specific 'good first issues' or areas in the codebase I should focus on to demonstrate my C++ proficiency for this specific project? Also, is there a preference for B-Rep based export or is the initial focus strictly on single mesh-to-STEP conversion?

[t-paul]

I am particularly interested in the challenge of integrating these into the existing OpenSCAD build pipeline across all three platforms. I am currently setting up the local development environment to explore the current export logic.

That's already a big goal, with GSoC being time limited with hard deadlines for each of the steps, it would be completely acceptable to focus on one platform and leave the others as optional topic for the end.

Could you please guide me on any specific 'good first issues' or areas in the codebase I should focus on to demonstrate my C++ proficiency for this specific project?

Issues in that category tend to be GUI topics, maybe #1155 which is mostly export related?

Also, is there a preference for B-Rep based export or is the initial focus strictly on single mesh-to-STEP conversion?

I'd say an initial single-mesh export would be a useful first step to get things integrated and stepping stone for further extension. The goal is certainly to keep as much information as possible, but that could be a bit too much for a single GSoC timeline. Defining the scope is part of the application process, so it's a good discussion if there's any minimum implementation to look at without the need to require everything to be implemented before a file is exported.

[arybhatt4533]

@t-paul I've reviewed issue #1155. It seems like a great way to understand how OpenSCAD handles mesh data (points and faces). I plan to start by looking at the existing STL export implementation to see how it traverses the geometry and then implement a similar logic for polyhedron() output. This will definitely help me build the foundation for the STEP export project

[t-paul]

Note that while jumping fully into coding is tempting, the GSoC process requires a project proposal. Getting to know OpenSCAD code in general via the initial PR is an important step, but the most important one is discussing and preparing a well written project proposal to be posted on the GSoC dashboard once the application period opens in a couple of days.

[arybhatt4533]

Hello @t-paul
Thank you for the advice! I am currently finalizing the initial PR for Issue #1155 (polyhedron export).
At the same time, I am also preparing my GSoC project proposal. Once the draft is ready, would you be able to review it and provide some feedback? I want to ensure that there are no gaps and that it perfectly aligns with OpenSCAD's standards.
Thanks again for your guidance