three.js/examples/js/exporters/OBJExporter.js

( function () {

	class OBJExporter {

		parse( object ) {

			let output = '';
			let indexVertex = 0;
			let indexVertexUvs = 0;
			let indexNormals = 0;
			const vertex = new THREE.Vector3();
			const color = new THREE.Color();
			const normal = new THREE.Vector3();
			const uv = new THREE.Vector2();
			const face = [];

			function parseMesh( mesh ) {

				let nbVertex = 0;
				let nbNormals = 0;
				let nbVertexUvs = 0;
				const geometry = mesh.geometry;
				const normalMatrixWorld = new THREE.Matrix3(); // shortcuts

				const vertices = geometry.getAttribute( 'position' );
				const normals = geometry.getAttribute( 'normal' );
				const uvs = geometry.getAttribute( 'uv' );
				const indices = geometry.getIndex(); // name of the mesh object

				output += 'o ' + mesh.name + '\n'; // name of the mesh material

				if ( mesh.material && mesh.material.name ) {

					output += 'usemtl ' + mesh.material.name + '\n';

				} // vertices


				if ( vertices !== undefined ) {

					for ( let i = 0, l = vertices.count; i < l; i ++, nbVertex ++ ) {

						vertex.fromBufferAttribute( vertices, i ); // transform the vertex to world space

						vertex.applyMatrix4( mesh.matrixWorld ); // transform the vertex to export format

						output += 'v ' + vertex.x + ' ' + vertex.y + ' ' + vertex.z + '\n';

					}

				} // uvs


				if ( uvs !== undefined ) {

					for ( let i = 0, l = uvs.count; i < l; i ++, nbVertexUvs ++ ) {

						uv.fromBufferAttribute( uvs, i ); // transform the uv to export format

						output += 'vt ' + uv.x + ' ' + uv.y + '\n';

					}

				} // normals


				if ( normals !== undefined ) {

					normalMatrixWorld.getNormalMatrix( mesh.matrixWorld );

					for ( let i = 0, l = normals.count; i < l; i ++, nbNormals ++ ) {

						normal.fromBufferAttribute( normals, i ); // transform the normal to world space

						normal.applyMatrix3( normalMatrixWorld ).normalize(); // transform the normal to export format

						output += 'vn ' + normal.x + ' ' + normal.y + ' ' + normal.z + '\n';

					}

				} // faces


				if ( indices !== null ) {

					for ( let i = 0, l = indices.count; i < l; i += 3 ) {

						for ( let m = 0; m < 3; m ++ ) {

							const j = indices.getX( i + m ) + 1;
							face[ m ] = indexVertex + j + ( normals || uvs ? '/' + ( uvs ? indexVertexUvs + j : '' ) + ( normals ? '/' + ( indexNormals + j ) : '' ) : '' );

						} // transform the face to export format


						output += 'f ' + face.join( ' ' ) + '\n';

					}

				} else {

					for ( let i = 0, l = vertices.count; i < l; i += 3 ) {

						for ( let m = 0; m < 3; m ++ ) {

							const j = i + m + 1;
							face[ m ] = indexVertex + j + ( normals || uvs ? '/' + ( uvs ? indexVertexUvs + j : '' ) + ( normals ? '/' + ( indexNormals + j ) : '' ) : '' );

						} // transform the face to export format


						output += 'f ' + face.join( ' ' ) + '\n';

					}

				} // update index


				indexVertex += nbVertex;
				indexVertexUvs += nbVertexUvs;
				indexNormals += nbNormals;

			}

			function parseLine( line ) {

				let nbVertex = 0;
				const geometry = line.geometry;
				const type = line.type; // shortcuts

				const vertices = geometry.getAttribute( 'position' ); // name of the line object

				output += 'o ' + line.name + '\n';

				if ( vertices !== undefined ) {

					for ( let i = 0, l = vertices.count; i < l; i ++, nbVertex ++ ) {

						vertex.fromBufferAttribute( vertices, i ); // transform the vertex to world space

						vertex.applyMatrix4( line.matrixWorld ); // transform the vertex to export format

						output += 'v ' + vertex.x + ' ' + vertex.y + ' ' + vertex.z + '\n';

					}

				}

				if ( type === 'Line' ) {

					output += 'l ';

					for ( let j = 1, l = vertices.count; j <= l; j ++ ) {

						output += indexVertex + j + ' ';

					}

					output += '\n';

				}

				if ( type === 'LineSegments' ) {

					for ( let j = 1, k = j + 1, l = vertices.count; j < l; j += 2, k = j + 1 ) {

						output += 'l ' + ( indexVertex + j ) + ' ' + ( indexVertex + k ) + '\n';

					}

				} // update index


				indexVertex += nbVertex;

			}

			function parsePoints( points ) {

				let nbVertex = 0;
				const geometry = points.geometry;
				const vertices = geometry.getAttribute( 'position' );
				const colors = geometry.getAttribute( 'color' );
				output += 'o ' + points.name + '\n';

				if ( vertices !== undefined ) {

					for ( let i = 0, l = vertices.count; i < l; i ++, nbVertex ++ ) {

						vertex.fromBufferAttribute( vertices, i );
						vertex.applyMatrix4( points.matrixWorld );
						output += 'v ' + vertex.x + ' ' + vertex.y + ' ' + vertex.z;

						if ( colors !== undefined ) {

							color.fromBufferAttribute( colors, i ).convertLinearToSRGB();
							output += ' ' + color.r + ' ' + color.g + ' ' + color.b;

						}

						output += '\n';

					}

					output += 'p ';

					for ( let j = 1, l = vertices.count; j <= l; j ++ ) {

						output += indexVertex + j + ' ';

					}

					output += '\n';

				} // update index


				indexVertex += nbVertex;

			}

			object.traverse( function ( child ) {

				if ( child.isMesh === true ) {

					parseMesh( child );

				}

				if ( child.isLine === true ) {

					parseLine( child );

				}

				if ( child.isPoints === true ) {

					parsePoints( child );

				}

			} );
			return output;

		}

	}

	THREE.OBJExporter = OBJExporter;

} )();