三塊OBJ加載程序從塊中缺少幾何面

從Google塊中加載一些OBJ我注意到有幾個面遺失。我有平滑的陰影，但不能讓失蹤的臉出現。想法？這是我當前模板：三塊OBJ加載程序從塊中缺少幾何面

mtlLoader.load(mtlUrl, (materialLoader) => { 
     materialLoader.preload(); 

     for (let material in materialLoader.materials) { 
      materialLoader.materials[material].side = THREE.DoubleSide; 
     } 

     let objLoader = new THREE.OBJLoader(); 
     objLoader.setMaterials(materialLoader); 

     let onSuccess = function (object) { 
      var mesh = object.children[0]; 
      mesh.geometry = new THREE.Geometry().fromBufferGeometry(mesh.geometry); 
      mesh.geometry.computeFaceNormals(); 
      mesh.geometry.mergeVertices(); 
      mesh.geometry.computeVertexNormals(); 
      mesh.geometry.center(); 

      this.group.add(object);     
     }; 

     let onProgress = function (event) { 
      if (event.lengthComputable) { 
       let percentComplete = event.loaded/event.total * 100; 
       let output = 'Download of Object: ' + Math.round(percentComplete) + '%'; 
      } 
     }; 

     let onError = function (event) { 
      let output = 'Error of type "' + event.type + '" occurred when trying to load: ' + event.src; 
     }; 

     objLoader.load(objUrl, onSuccess, onProgress, onError); 
    });

工件：