New issue 1097: [experimental] Default field for use in VR https://bitbucket.org/yt_analysis/yt/issues/1097/experimental-default-field-... Cameron Hummels: When making a VR, it defaults to using the first field in the field_name list if a field is not specified, which almost never gives the desired result. Perhaps just default to ('gas', 'density') like the PW plots do? Implicitly assumed in examples (ie cookbook recipe: camera_movement.py)