Export a three js textured model to a .OBJ with .MTL file

Question

I would like to be able to export an obj file just like in this example http://threejs.org/examples/#webgl_exporter_obj

However, i would like to export the .obj file with corresponding textures in the .mtl texture file (i have seen obj files with "usemtl someTextureNameFromMTL")

I have seen this question but the exporter seems to be exporting only mesh. I have also found this question but that discusses importer only.

The thing i wanted to implement is to make a 3d printable editor that would also export textures/colors, as there already is a .stl mesh exporter for 3d printing. however, i have found no mesh+color/texture exporter for three js :(

Answer 1

I have extended the OBJExporter a little bit. It will return an object containing the .obj part and the .mtl part. I just wrote it down without testing, so there are probably bugs, but I hope it is something to start with.

I haven't looked up all the mtl values, I just used some standards values apart from color and texture information. Maybe I will improve it later on. You also need to be aware of the mtl filename. Currently, I'm writing a static name to the obj part. When you save the files the mtl file needs to be the same name as in the obj file declared. Otherwise 3ds max etc. won't read it.

/**
 * @author mrdoob / http://mrdoob.com/
 */

THREE.OBJExporter = function () {};

THREE.OBJExporter.prototype = {

	constructor: THREE.OBJExporter,

	parse: function ( object ) {

	var output = '';
		var materials = {};

		var indexVertex = 0;
		var indexVertexUvs = 0;
		var indexNormals = 0;
      	
	var mtlFileName = 'objmaterial'; // maybe this value can be passed as parameter
	output += 'mtllib ' + mtlFileName +  '.mtl\n';

		var parseMesh = function ( mesh ) {

			var nbVertex = 0;
			var nbVertexUvs = 0;
			var nbNormals = 0;

			var geometry = mesh.geometry;
			var material = mesh.material;

			if ( geometry instanceof THREE.Geometry ) {

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

				var vertices = geometry.vertices;

				for ( var i = 0, l = vertices.length; i < l; i ++ ) {

					var vertex = vertices[ i ].clone();
					vertex.applyMatrix4( mesh.matrixWorld );

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

					nbVertex ++;

				}

				// uvs

				var faces = geometry.faces;
				var faceVertexUvs = geometry.faceVertexUvs[ 0 ];
				var hasVertexUvs = faces.length === faceVertexUvs.length;

				if ( hasVertexUvs ) {

					for ( var i = 0, l = faceVertexUvs.length; i < l; i ++ ) {

						var vertexUvs = faceVertexUvs[ i ];

						for ( var j = 0, jl = vertexUvs.length; j < jl; j ++ ) {

							var uv = vertexUvs[ j ];

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

							nbVertexUvs ++;

						}

					}

				}

				// normals

				var normalMatrixWorld = new THREE.Matrix3();
				normalMatrixWorld.getNormalMatrix( mesh.matrixWorld );

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

					var face = faces[ i ];
					var vertexNormals = face.vertexNormals;

					if ( vertexNormals.length === 3 ) {

						for ( var j = 0, jl = vertexNormals.length; j < jl; j ++ ) {

							var normal = vertexNormals[ j ].clone();
							normal.applyMatrix3( normalMatrixWorld );

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

							nbNormals ++;

						}

					} else {

						var normal = face.normal.clone();
						normal.applyMatrix3( normalMatrixWorld );

						for ( var j = 0; j < 3; j ++ ) {

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

							nbNormals ++;

						}

					}

				}
              
			// material
              
			if (material.name !== '')
				output += 'usemtl ' + material.name + '\n';
			else
				output += 'usemtl material' + material.id + '\n';
              
			materials[material.id] = material;

				// faces


				for ( var i = 0, j = 1, l = faces.length; i < l; i ++, j += 3 ) {

					var face = faces[ i ];

					output += 'f ';
					output += ( indexVertex + face.a + 1 ) + '/' + ( hasVertexUvs ? ( indexVertexUvs + j     ) : '' ) + '/' + ( indexNormals + j     ) + ' ';
					output += ( indexVertex + face.b + 1 ) + '/' + ( hasVertexUvs ? ( indexVertexUvs + j + 1 ) : '' ) + '/' + ( indexNormals + j + 1 ) + ' ';
					output += ( indexVertex + face.c + 1 ) + '/' + ( hasVertexUvs ? ( indexVertexUvs + j + 2 ) : '' ) + '/' + ( indexNormals + j + 2 ) + '\n';

				}

			} else {

				console.warn( 'THREE.OBJExporter.parseMesh(): geometry type unsupported', mesh );
				// TODO: Support only BufferGeometry and use use setFromObject()

			}

			// update index
			indexVertex += nbVertex;
			indexVertexUvs += nbVertexUvs;
			indexNormals += nbNormals;

		};

		object.traverse( function ( child ) {

			if ( child instanceof THREE.Mesh ) parseMesh( child );

		} );
      		
	// mtl output
      
	var mtlOutput = '';
      
	for (var key in materials) {
        
		var mat = materials[key];
          
		if (mat.name !== '')
			mtlOutput += 'newmtl ' + mat.name + '\n';
		else
			mtlOutput += 'newmtl material' + mat.id + '\n';
          
		mtlOutput += 'Ns 10.0000\n';
		mtlOutput += 'Ni 1.5000\n';
		mtlOutput += 'd 1.0000\n';
		mtlOutput += 'Tr 0.0000\n';
		mtlOutput += 'Tf 1.0000 1.0000 1.0000\n';
		mtlOutput += 'illum 2\n';
		mtlOutput += 'Ka ' + mat.color.r + ' ' + mat.color.g + ' ' + mat.color.b + ' ' + '\n';
		mtlOutput += 'Kd ' + mat.color.r + ' ' + mat.color.g + ' ' + mat.color.b + ' ' + '\n';
		mtlOutput += 'Ks 0.0000 0.0000 0.0000\n';
		mtlOutput += 'Ke 0.0000 0.0000 0.0000\n';
          
		if (mat.map && mat.map instanceof THREE.Texture) {
          
			var file = mat.map.image.currentSrc.slice( mat.map.image.currentSrc.slice.lastIndexOf("/"), mat.map.image.currentSrc.length - 1 );
            
			mtlOutput += 'map_Ka ' + file + '\n';
			mtlOutput += 'map_Kd ' + file + '\n';
            
		}
          
	}

	return {
		obj: output,
		mtl: mtlOutput
	}

	}

};