Any X3D scene can be integrated into the Scene by using the <inline> node. The X3D model has be be stored on a web server. The X3D file should be optimized using aopt. It is not necessary, but usually improves performance a lot.
<html> <head> <title> External File e</title> <script type='text/javascript' src='http://www.x3dom.org/download/x3dom.js'> </script> <link rel='stylesheet' type='text/css' href='http://www.x3dom.org/download/x3dom.css'></link> </head> <body> <X3D id="shapedata"> <Scene> <background transparency='0' skyColor='1 1 1'></background> <inline url="HFT_Bau1_0.x3d"></inline> </Scene> </X3D> </body> </html>