Simple STL utils

Currently, just an STL parser and writer. It handles the most popular ASCII and binary formats. It can read an entire buffer synchronously, or read a stream on-the-fly. It writes via a transform stream.

Reading

Synchronous immediate

var data = fs.readFileSync('gear.stl');
var stl = STLParser.parse(data [, options] );

stl = {
	format: ...,
	header: { ... },
	triangles: [{ normal: vector, vertices: [vector, ...] }, ...]
};

Pseudo-asynchronous steam

fs.createReadStream('gear.stl')
	.pipe(new STLParser.ParseStream( [options] ))
	.on('format', function (format) {
	})
	.on('header', function (header) {
	})
	.on('data', function (triangle) {
	})
	.on('error', ...)
	.on('finish', ...);

I called this "pseudo" asynchronous because the actual parsing is done by JS code, so is blocking and synchronous. The stream wrapper provides an asynchronous transform-stream interface around the parser, allowing sockets and files to be easily streamed through the parser.

If you're reading from a stream, but want the entire STL object, the transform stream has a construct method which will stream in the entire model and give a single result in the same format as the non-streaming method:

fs.createReadStream('gear.stl')
	.pipe(new STL.ParseStream())
	.construct()
	.on('data', function (chunk) {
		/* Callback only called once */
		/* chunk is entire STL model in same format that STLParser returns */
	})
	.on('finish', function () {
	});

Result formats

• format is either binary or ascii.

• header is either:

  • ascii format: { name: 'solid name' }

  • binary format: { data: <80-byte buffer>, count: number }

• triangles is an array of triangle.

• triangle is:

   {
       normal: [nx, ny, nz],
       vertices: [
           [v1x, v1y, v1z],
           [v2x, v2y, v2z],
           [v3x, v3y, v3z]
       ]
   }
  

  For binary format, each triangle also contains an attr property containing a 16-bit integer value which has no standardized meaning.

Notes

The parser strictly enforces syntax, and disallows unfamiliar tokens. It does not however perform any validation on the geometry data, including:

• Winding direction of vertices

• Normal agreeing with direction implied by vertices

Some parse errors can be disabled by setting lax: true in the parser options. With lax mode enabled, the following deviations from the standard are permitted:

• Non-positive values are permitted in vertex vectors

• Tabs may also be used as whitespace in ASCII format

• Garbage at end of lines is ignored

• name after endsolid does not have to match name after solid

Writing

Streaming

The writer is a transform stream. Initialize it with header data and triangle count, then stream the triangles in:

/* AsciiWriter requires solid name and triangle count */
var writer = new STL.AsciiWriter('name', numTriangles);

/* BinaryWriter requires header buffer/string and triangle count */
var writer = new STL.BinaryWriter(null, numTriangles);

/* Either/both of the following may be called multiple times */
writer.write(individualTriangle);
writer.write(arrayOfTriangles);

All at once

When initialized without header data, then writer will accept the entire STL object (including headers) in one call to write:

/* No parameters */
var writer = new STL.AsciiWriter();

/* One write call, with the entire STL object */
writer.write(parsedStlObject);
	.pipe(...);