Exports a THREE.js scene mesh to STL, making it suitable for 3d printing

gistfile1.txt

/**
 * Based on https://github.com/mrdoob/three.js/blob/a72347515fa34e892f7a9bfa66a34fdc0df55954/examples/js/exporters/STLExporter.js
 * extended from https://gist.github.com/kjlubick/fb6ba9c51df63ba0951f
 * Tested on r68 and r70
 * @author kjlubick / https://github.com/kjlubick
 * @author kovacsv / http://kovacsv.hu/
 * @author mrdoob / http://mrdoob.com/
 */
THREE.STLExporter = function () {};

THREE.STLExporter.prototype = {

	constructor: THREE.STLExporter,

	parse: ( function () {

		var vector = new THREE.Vector3();
		var normalMatrixWorld = new THREE.Matrix3();

		return function ( scene ) {

			var output = '';

			output += 'solid exported\n';

			scene.traverse( function ( object ) {

				if ( object instanceof THREE.Mesh ) {

					var geometry = object.geometry;
					var skeleton = object.skeleton;
					var matrixWorld = object.matrixWorld;
					var mesh = object;

                    if (geometry instanceof THREE.BufferGeometry)
                    {
                        geometry = new THREE.Geometry().fromBufferGeometry( geometry );
                    }

					if ( geometry instanceof THREE.Geometry ) {

						var vertices = geometry.vertices;
						var faces = geometry.faces;

						normalMatrixWorld.getNormalMatrix( matrixWorld );

						for ( var i = 0, l = faces.length; i < l; i ++ ) {
							var face = faces[ i ];

							vector.copy( face.normal ).applyMatrix3( normalMatrixWorld ).normalize();

							output += '\tfacet normal ' + vector.x + ' ' + vector.y + ' ' + vector.z + '\n';
							output += '\t\touter loop\n';

							var indices = [ face.a, face.b, face.c ];

							for ( var j = 0; j < 3; j ++ ) {
								var vertexIndex = indices[ j ];
								if (geometry.skinIndices.length == 0) {
									vector.copy( vertices[ vertexIndex ] ).applyMatrix4( matrixWorld );
									output += '\t\t\tvertex ' + vector.x + ' ' + vector.y + ' ' + vector.z + '\n';
								} else {
									vector.copy( vertices[ vertexIndex ] ); //.applyMatrix4( matrixWorld );
									
									// see https://github.com/mrdoob/three.js/issues/3187
									boneIndices = [];
									boneIndices[0] = geometry.skinIndices[vertexIndex].x;
									boneIndices[1] = geometry.skinIndices[vertexIndex].y;
									boneIndices[2] = geometry.skinIndices[vertexIndex].z;
									boneIndices[3] = geometry.skinIndices[vertexIndex].w;
									
									weights = [];
									weights[0] = geometry.skinWeights[vertexIndex].x;
									weights[1] = geometry.skinWeights[vertexIndex].y;
									weights[2] = geometry.skinWeights[vertexIndex].z;
									weights[3] = geometry.skinWeights[vertexIndex].w;
									
									inverses = [];
									inverses[0] = skeleton.boneInverses[ boneIndices[0] ];
									inverses[1] = skeleton.boneInverses[ boneIndices[1] ];
									inverses[2] = skeleton.boneInverses[ boneIndices[2] ];
									inverses[3] = skeleton.boneInverses[ boneIndices[3] ];

									skinMatrices = [];
									skinMatrices[0] = skeleton.bones[ boneIndices[0] ].matrixWorld;
									skinMatrices[1] = skeleton.bones[ boneIndices[1] ].matrixWorld;
									skinMatrices[2] = skeleton.bones[ boneIndices[2] ].matrixWorld;
									skinMatrices[3] = skeleton.bones[ boneIndices[3] ].matrixWorld;
									
									var finalVector = new THREE.Vector4();
									for(var k = 0; k<4; k++) {
										var tempVector = new THREE.Vector4(vector.x, vector.y, vector.z);
										tempVector.multiplyScalar(weights[k]);
										//the inverse takes the vector into local bone space
										tempVector.applyMatrix4(inverses[k])
										//which is then transformed to the appropriate world space
										.applyMatrix4(skinMatrices[k]);
										finalVector.add(tempVector);
									}
									output += '\t\t\tvertex ' + finalVector.x + ' ' + finalVector.y + ' ' + finalVector.z + '\n';
								}
							}
							output += '\t\tendloop\n';
							output += '\tendfacet\n';
						}
					}
				}

			} );

			output += 'endsolid exported\n';

			return output;
		};
	}() )
};