To dimension structural rebar, select the Host category (wall, column, beam, etc.) to be included in total measure:
Then, define Structural Rebar dimensioning settings. It's similar to other Categories, but there are a few differences, which are described here.
Rebar visibility - here you can select options that will be applied on the relevant view while you are using Smart Dimensions alone or with Smart Assemblies.
View as Solid - turns ON solid visibility for rebar. Works only in 3D views.
View Unobscured - by default this is turned ON in Revit, but sometimes it needs to be switched OFF so that bars inside of an element will not be visible.
Hide - it will hide rebar in the view if configuration with this option On is used. Use it together with Filter, to hide only selected rebar.
Rebar Set Presentation - you can select to show middle or first and last bars of rebar sets in the view.
These options work even if no dimensioning is selected.
It works with the Filtering options above, so it could be applied only to selected bars. Just check all options that you have in the Dimensioning 1, Dimensioning 2, etc. tabs to make sure settings do not overwrite each other.
Additional options to quickly filter rebar. These will work with the Filtering options above.
All - Dimensioning 1 settings will be applied to all rebar visible in the view (if Filtering options don't dictate otherwise)
Area reinforcement - only bars created with Area reinforcement will be dimensioned
Path reinforcement - only bars created with Path reinforcement will be dimensioned
Single Bar - only bars created as singles will be dimensioned
Rebar sets - only Rebar sets will be dimensioned
Fabric sheets - only Fabric sheets will be dimensioned. (As of 2021 04 13, this option does not yet work, as settings for Fabric sheet dimensioning are still in development.)
Standard or Stirrup/Tie options let you quickly access filtering by Rebar style.
You can use Text Notes as for all the other Categories in Smart Dimensions, as well as Rebar tags.
To use Tags, choose this in the Text Note tab:
And in the Horizontal Elements, Vertical Elements, Element Sections, and Parallel in View tabs, you will find an option to select Rebar Tag Type:
Vertical / Horizontal Elements in view
Bars with hooks are treated as vertical or horizontal.
If it's sketched as bending or hooks, then it will fall into the Parallel in View dimensioning tab.
Element Sections - if we see the end of the bar, then it could be a section or an elevation view, but we're referring here to the circle that you see on-end.
Parallel in View - bars sketched parallel to the view plane