Office Web apps server 2013

I am trying to create office web apps server 2013 and installed the service.

But here have some problem when I deploy a single-server Office Web Apps Server farm.

PS C:\Users\Administrator> New-OfficeWebAppsFarm –InternalURL "http://servername" –AllowHttp -EditingEnabl
New-OfficeWebAppsFarm : The operation failed. The server did not meet the following prerequisites:
- The server must be joined to a domain.
At line:1 char:1
+ New-OfficeWebAppsFarm –InternalURL "http://servername" –AllowHttp -EditingEnable ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotInstalled: (:) [New-OfficeWebAppsFarm], InvalidOperationException
    + FullyQualifiedErrorId : PrerequisiteFailure,Microsoft.Office.Web.Apps.Administration.NewFarmCommand

Would I ask the question for the office web server must join to a domain?

Any way can setup success without join to a domain?

Thanks