Why POVRay renders fields and sometimes just doesn’t get displayed?

The reason for the failure of the default export into POVRay might be that the variant of your POVRay is of 3.0 version. The same could be the reason for POVRay not getting displayed without any report of an error. Terraform functions with 3.1 version and if you have a 3.0 version of POVRay, then you should use --pov30 switch for informing about this issue to terraform.

For checking your version of POVRay, you have to just type POVRay and look into output's first line. It will be having the version number in the first line itself.