If you changes the segments of Plane or Cube which I have noticed, the result may have UV mapping error.
I have the following code

              plane = new Plane();
      plane.width = 500;
      plane.height = 500;
      plane.bothsides = true;
      plane.segmentsH = 1;
      plane.segmentsW = 1;
      plane.material = new BitmapFileMaterial(”“);
      scene.addChild(plane);

      StartToRender();
      stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown);
  }

  protected function onKeyDown(E:KeyboardEvent):void{
      if(E.keyCode == Keyboard.F3){
        plane.width += 3;
        plane.segmentsW ++
      }
      if(E.keyCode == Keyboard.F4){
        plane.height += 3;
        plane.segmentsH ++
      }
  }

I think I have found out where caused this problem after a days time reading the source code of Away3d 3.6.
This bug may appear when you use the BitmapMaterial, For the render rendering a triangle face, it calls the renderTriangle
method of the BitmapMaterial. In BitmapMaterial, it used a dictionary called _faceDictionary to store the uvt data of the face , when the uv data changed in the faces, the _faceDictionary did not changes, so it caused the problem. To sets the invalidated property of the _faceMaterialVO in dictionary _faceDictionary may fix this bug. I extends the BitmapMaterial and add a new method to update this, it works.

Great, I’m glad you were able to solve it. If you want to modify BitmapMaterial (or any other part of the engine) to fix this bug, please feel free to file a pull request to the away3d-core-fp10 repository on GitHub and we could potentially merge it.

Sorry for long time to response to you.

I am honored that I was able to have the opportunity to contributing a little to away3d

I have changed two files, BitmapMaterial.asand TransformBitmapMaterial.as, added one function, modified two function.

I have added function:

in BitmapMaterial.as  at line 83, and added one line:

in function updateMaterial of BitmapMaterial and TransformBitmapMaterial.

The attachment comes with the final files.