Is there have tools to create quantized-mesh offline?

I know there has a tools named CTB,but the tools has bug,quantized-mesh created by CTB has no metadata extension.We coding in offline mode,so is there have tools to create quantized-mesh offline?

You can take a look at here
https://portal.terrainserver.com/

Thanks.I’ve visited the sample page,and found the page has some error info. In addition the terrain server need purchase.Is there any open source tools else ?