Implemented OpenSCAD support to models in STEP format.

[codex826]

Pull Request: Add OpenSCAD Support for Exporting Models in STEP Format

Issue no: #111

🚀 Overview

This PR introduces the foundational groundwork for exporting OpenSCAD models to the STEP (ISO-10303-21 AP214) format. Unlike the traditional approach of exporting a single rendered mesh, this implementation provides a modular geometry engine and a faceted B-Rep writer capable of preserving individual solid structures within a single export file.

This work fulfills the GSoC 3D-CAD project objective to simplify workflows for CNC manufacturing and electronics design (e.g., KiCAD integration) by removing the need for external STL-to-STEP conversion tools.

🏗 Solution Implementation

1. Research & Analysis

• Library Research: We investigated various libraries for STEP generation and chose a decoupled approach using openscad-parser for AST processing combined with a custom-built B-Rep generation engine. This avoids heavy external dependencies while ensuring full control over the STEP entity graph.
• STEP Investigation: We researched STEP AP203/AP214 standards and identified FACETED_BREP as the optimal initial target for robust faceted geometry exchange between OpenSCAD and tools like KiCAD or FreeCAD.

2. Core Implementation (src/)

• Geometry Engine (geometry.ts): Implements 3D math (Vectors, Matrix4) and mesh-level CSG operations.
  • Solid Primitives: cube, sphere, cylinder.
  • Booleans: union, difference, intersection.
  • Convex Hull: Standalone 3D incremental hull algorithm.
  • Extrusions: linear_extrude with twist and scale support.
• STEP Exporter (step-exporter.ts): Converts internal Solid geometry into valid ISO-10303-21 STEP entities (CLOSED_SHELL, FACE_SURFACE, POLY_LOOP).
• AST Evaluator (step-evaluator.ts): A tree-walking interpreter that translates OpenSCAD code (modules, functions, loops) into geometry primitives.

3. Integrated Tooling

• Validator (step-validator.ts): Ensures generated files have no dangling references and follow the STEP structural specification.
• CLI (cli.ts): A standalone tool for batch conversion and validation.

🛠 Tech Stack

• Language: TypeScript (ESM)
• Runtime: Node.js
• Parser: openscad-parser
• Math: Custom 3D Linear Algebra implementation.
• Testing: Custom regression suite with Node.js assert.

🧪 Testing & Verification

We have implemented a comprehensive test suite in src/tests/ that verifies:

• Geometric Accuracy: Math kernels and primitive generation.
• CSG Correctness: Booleans and Hulls.
• STEP Integrity: Structural validation of exported files.
• Language Support: For-loops, nested modules, and variables.

🔮 Future Aspects & Advanced Models

The current focus was on building the "ground work" for detailed models:

• B-Rep Advancement: The system is architected to support ADVANCED_BREP (smooth surfaces/NURBS) in the future by extending the Face definition to support analytic surfaces.
• Assembly Support: We have prototyped the ability to export multiple separate solids in one STEP file, allowing individual parts of an OpenSCAD assembly to be selected in target CAD tools.
• Build System Integration: The project is structured as a standard NPM package, ready to be integrated into CI/CD pipelines or desktop installers.

---

Created as part of the GSoC 3D-CAD initiative.

Pull Request: Add OpenSCAD Support for Exporting Models in STEP Format

🚀 Overview

This PR introduces the foundational groundwork for exporting OpenSCAD models to the STEP (ISO-10303-21 AP214) format. Unlike the traditional approach of exporting a single rendered mesh, this implementation provides a modular geometry engine and a faceted B-Rep writer capable of preserving individual solid structures within a single export file.

This work fulfills the GSoC 3D-CAD project objective to simplify workflows for CNC manufacturing and electronics design (e.g., KiCAD integration) by removing the need for external STL-to-STEP conversion tools.

🏗 Solution Implementation

1. Research & Analysis

• Library Research: We investigated various libraries for STEP generation and chose a decoupled approach using openscad-parser for AST processing combined with a custom-built B-Rep generation engine. This avoids heavy external dependencies while ensuring full control over the STEP entity graph.
• STEP Investigation: We researched STEP AP203/AP214 standards and identified FACETED_BREP as the optimal initial target for robust faceted geometry exchange between OpenSCAD and tools like KiCAD or FreeCAD.

2. Core Implementation (src/)

• Geometry Engine (geometry.ts): Implements 3D math (Vectors, Matrix4) and mesh-level CSG operations.
  • Solid Primitives: cube, sphere, cylinder.
  • Booleans: union, difference, intersection.
  • Convex Hull: Standalone 3D incremental hull algorithm.
  • Extrusions: linear_extrude with twist and scale support.
• STEP Exporter (step-exporter.ts): Converts internal Solid geometry into valid ISO-10303-21 STEP entities (CLOSED_SHELL, FACE_SURFACE, POLY_LOOP).
• AST Evaluator (step-evaluator.ts): A tree-walking interpreter that translates OpenSCAD code (modules, functions, loops) into geometry primitives.

3. Integrated Tooling

• Validator (step-validator.ts): Ensures generated files have no dangling references and follow the STEP structural specification.
• CLI (cli.ts): A standalone tool for batch conversion and validation.

🛠 Tech Stack

• Language: TypeScript (ESM)
• Runtime: Node.js
• Parser: openscad-parser
• Math: Custom 3D Linear Algebra implementation.
• Testing: Custom regression suite with Node.js assert.

🧪 Testing & Verification

I have implemented a comprehensive test suite in src/tests/ that verifies:

• Geometric Accuracy: Math kernels and primitive generation.
• CSG Correctness: Booleans and Hulls.
• STEP Integrity: Structural validation of exported files.
• Language Support: For-loops, nested modules, and variables.

🔮 Future Aspects & Advanced Models

The current focus was on building the "ground work" for detailed models:

• B-Rep Advancement: The system is architected to support ADVANCED_BREP (smooth surfaces/NURBS) in the future by extending the Face definition to support analytic surfaces.
• Assembly Support: We have prototyped the ability to export multiple separate solids in one STEP file, allowing individual parts of an OpenSCAD assembly to be selected in target CAD tools.
• Build System Integration: The project is structured as a standard NPM package, ready to be integrated into CI/CD pipelines or desktop installers.

---

Created as part of the GSoC 3D-CAD initiative.

[t-paul]

I'm not sure what this is targeting, it references issue #111 but does not match with the topic of that issue.