Can any .X (DirectX 3D object) be used as progressive mesh?

I'm learning about Direct3D's progressive mesh. I tried the SDK sample (ProgressiveMesh) and fiddle with the code to replace the default object with some other .X file.

The application works sometimes with some .X files but not all, especially when the file size is big and it crashes.

Can anyway tell me if any .X object can be used as a progressive mesh? Does the example automatically convert the object into a progressive mesh? If not, then how can I obtain a progressive mesh fil开发者_如何学Ce so that I can load it into the SDK sample?

Thanks!

IDK what you plan on doing with your models, but you might want to look into using FBX files using the FBX_SDK.