Add a ruler tool to calculate distances between 2 points on surfaces in the 3D geometry view
It is often useful to check distance between parts of a 3D geometry you are viewing and processing. This could be achieved with a ruler tool That would give not only the distance magnitude between two points, but also x, y and z distances.
I believe it is Sources -> Ruler.
Cory Quammen commented
This is possible in ParaView 5.4.1. With your geometry source selected, choose Filters -> Ruler. You can move the endpoints of the ruler to different geometries with the mouse cursor. Alternatively, you can snap the end points to the surface. See the instructions in the Pipeline browser that tell you how to pick points on the surface, including snapping to the nearest points on the geometry. After clicking Apply, the Ruler will show you the distance. It does not display the distance in x, y, or z separately, but you can get the endpoint locations from the Pipeline panel to manually compute those.