If the default export to POVRay fails or if it just isn't displayed (even though no error is reported), it could be that your POVRay is of version 3.0, while Terraform expects version 3.1. If you are using version 3.0, use the --pov30 switch to inform terraform of this.
Alternativeley you can use the --debug 255 switch to have the actual povray output echoed to the standard output. This output should help you figure out what is being done going and what is going wrong.
To see what POVRay version you have installed, simply type povray and the first line of output displayed will contain the version number.