NVF Loading Method 
 STEP1 Load NVF to the MhcModule. 
 STEP2 Make the loaded MhcModule active. 
 STEP3 If all MhcModules have been loaded, bind the MhcScene. 
 (However, STEP2~STEP3 MUST NOT be executed in parallel with scene evaluation.) 

  Example: 
    int LoadScene( MhcScene *scene_ptr,
		   MisInput *input_ptr,
		   MifFileParser *parser_ptr )
    {
	mhcModuleLoad( /* Load module 1*/, parser_ptr, input_ptr );
	mhcModuleLoad( /* Load module 2 */, parser_ptr, input_ptr );
	   ....

	/* From here on must not be executed in parallel with scene evaluation */
	mhcModuleActivate( /* Loaded module 1 */ );
	mhcModuleActivate( /* Loaded module 2 */ );
	   ....

	mhcSceneBind( scene_ptr );
    }

  The entire scene does not necessarily have to be loaded at once.  However, once loading has been 
  completed, it is absolutely necessary to call mhcSceneBind() before executing scene evaluation. 

NVF Unloading Method 
 STEP1 Make the loaded MhcModule inactive. 
 STEP2 Unload NVF to the MhcModule. 
 STEP3 If all MhcModules have been loaded, bind the MhcScene.
 (However, STEP1~STEP3 MUST NOT be executed in parallel with scene evaluation.) 

  Example: 
    int UnloadScene( MhcScene *scene_ptr )
    {
	mhcModuleInactivate( /* Loaded module 1 */ );
	mhcModuleInactivate( /* Loaded module 2 */ );
	   ....

	mhcModuleUnload( /* Loaded module 1 */ );
	mhcModuleUnload( /* Loaded module 1 */ );
	   ....

	mhcSceneBind( scene_ptr );
    }

  The entire scene does not necessarily have to be unloaded at once.  However, once unloading has been 
  completed, it is absolutely necessary to call mhcSceneBind() before executing scene evaluation. 

