The view's Discipline property serves three different functions within Revit:
There are six possible view Discipline values: Coordination, Architectural, Structural, Mechanical, Electrical, and Plumbing. The Coordination view will show all elements (un-shaded) and will also allow all elements to be selectable (as it relates to the View Discipline setting). In many cases this will be the simplest way of resolving the issue. As always, consult with your BIM Manager before modifying the Discipline setting for the view.
The View Discipline setting of Structural will only show Walls that are designated (by instance) as Structural. If this is the case, you can resolve the visibility issue by either changing the Discipline of the View from Structural to any other Discipline (Architectural or Collaboration are recommended), OR you can select the Structural checkbox of the wall element, as shown.
View References such as Elevation Markers, Section Marks, or Callouts must reference a View that has the same View Discipline setting as the View in which they are placed in order to be visible. For example, if both the Target View and the View Referenced by the marker are set to Coordination, the reference marker would display, assuming no other reasons are in-play.
Many Revit families have a built-in subcategory called 'Hidden Lines'. The display of elements that utilize this subcategory is controlled at the Object Styles level, in terms of line color and pattern. The visibility of these lines is controlled not only through Visibility Graphics, but also through a View property called "Show Hidden Lines". If you are missing an element that is typically shown with hidden lines, such as Structural Framing or Stairs, then you should review the "Show Hidden Lines" value along with the View Discipline setting.
Revit MEP Elements ignore the cut plane of the View Range when the Discipline is Mechanical, Electrical, Plumbing, or Coordination. For this reason, MEP elements such as light fixtures, conduit, pipes, etc. might be unexpectedly invisible when the Discipline is set to either Structural or Architectural.
Learn more in Revit Help - View Discipline
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