问JavaScript函数只适用于最后一个元素(Three.js)

EN

function generateFence(nb){
  
  // First we will load the model once, as we want to reuse it.
  // Lets wrap it in a promise so its easier to use later.
  
  const value = -5;
  const fences = new THREE.Group;
  const model = new Promise(function( resolve ){
  
    THREE.ColladaLoader( loadingManager ).load( 'fence/model.dae', resolve );
    
  });
  
  // Use a `let` declaration to ensure that each loop remembers 
  // what the value for i was wen it ran, even if you perform an async operation.
  
  for( let i = 0; i < nb; i++ ){
    
    // The bit after `then` happens asynchronously, waiting until the model is loaded
    // Because of this, we need to ensure we don't rely too much on values defined in the synchronous loop.
    
    model.then(model => {
      
      // Let's clone it so we create copies of the one model
      
      const fence = model.scene.clone();
      
      // Calculate the x position based on value and the current state of i.
      
      fence.position.set( value + i * 3, 0, -5 );
      fences.add( fence );
      
    });
    
  }
  
  return fences;
  
}

// Returns a THREE.Group. When the fences are loaded, they will 
// be added to the group, which is already an invisible part of the scene.
scene.add( generateFence(3) );

function generateFence(nb){
  const loader = new THREE.ColladaLoader();
  loader.load( 'fence/model.dae', function ( collada ) {
    const copy = collada.scene.clone();
    scene.add(copy);
    let value = -5;
    for(var i = 0; i < nb ; i++) {
      copy.position.x = value;
      copy.position.z = -5;
      value = value + 3;
    }
  });
}

generateFence(3);