Implementing STEP/STP File Support in Three.js

Based on the available information, Three.js doesn't have a built-in exporter or loader for STEP/STP files. These CAD formats are not directly supported in the standard Three.js library, which is why you've been having difficulty implementing this feature.

Possible Approaches

Since Three.js doesn't natively support STEP/STP formats, you'll need to use a conversion approach:

1. Convert to an intermediate format: Convert STEP/STP files to a format that Three.js does support (like GLTF, OBJ, or STL)

2. Use a third-party library: Implement a conversion pipeline using external tools

Implementation Considerations

Node.js Approach

If you're considering using Node.js for conversion, be aware that Three.js has some compatibility issues in Node.js environments:

• Three.js depends on browser objects and DOM APIs not available in Node.js
• Some issues can be resolved using libraries like headless-gl
• You'll need to enable ES6 modules in your Node.js project by adding { "type": "module" } to your package.json

Conversion Pipeline

A typical workflow might look like:

1. Use a CAD conversion library (outside of Three.js) to convert STEP/STP to a supported format
2. Import the converted file using one of Three.js's existing loaders
3. Render the model in your Three.js application

Potential Tools

You mentioned pythonocc, which is indeed one option for STEP file conversion. You could create a server-side conversion service that:

1. Accepts STEP/STP files
2. Converts them to a Three.js-compatible format (like GLTF or STL)
3. Returns the converted file for use in your Three.js application

Supported Export Formats

Once you've converted your STEP/STP files, you can use one of these Three.js exporters for further processing:

• GLTFExporter
• OBJExporter
• STLExporter
• PLYExporter
• DRACOExporter
• EXRExporter

The STL format might be particularly suitable for CAD models as it's commonly used in engineering applications.

Since there's no direct implementation guide available in the Three.js documentation, you'll need to create a custom solution combining these approaches based on your specific requirements.