Revit's most hidden commands

Recently I did a Revit demo of divided paths and repeaters.  Afterwards someone said they had spent a day trying to figure out one simple thing I showed - they searched everywhere, including Youtube for videos but could not find out how to control divided path node visibility in a project.  That got me thinking about some really hidden away commands and features in Revit that are not at all intuitive and are not clearly explained in the Wikihelp - so here are a couple of them:

Divided Path & Divided Surface Node Visibility

When you are in the Conceptual Massing Environment (CME) in Revit (Mass family, In-Place mass, Adaptive Component, Pattern-based family), there are two commands for dividing elements:   Divide Path & Divide Surface.
They behave slightly differently but have a common purpose and methodology as well as common problems.

Divided Path

When a linear element (line, arc, spline etc) is selected, a command becomes available: "Divide Path" - this does not affect the original element but places a new element on top, which is divided into a specified number of segments delineated by nodes.

These nodes show as blue dots, and can be used to snap onto.  There is no way to control the size or colour of the nodes - it is hard-coded into Revit.  The visibility of the nodes is also hard to control;  in fact, in the project environment they cannot be controlled at all - if they were visible in the family when it was loaded, then they will always be visible in the project, which can be very frustrating.  Don't waste your time looking for settings in "Visibility Graphics" or anywhere else in the project settings - you have to go back and edit the family to hide them:
In the family environment, select the divided path.  On the menu, it should display a panel called "Path Representation";  on the bottom right corner of the menu panel is a tiny black arrow.

Click on the arrow and it will open a Path Representation dialog box

This is where you can turn on or off the node visibility. Then you can save the family and load it into a project again.

Divided Surface

This works in a similar way and has the same visibility control problems, but of course it is inconsistent with the divided path in several ways:
1.   By default the nodes on a divided path are visible;  on a divided surface they are not, so you have to turn them on to see them!

2.  The number on a divided path refers to the number of nodes;  on a surface it refers to the number of segments - thus the same number would result in one extra node on a surface relative to a path

3. Surface representation has additional options related to grids, lines and patterns.

However, if  all three checkboxes are unticked, it still displays the original surface and it seems that there is no way to turn off its visibility - ie the "Original Surface" checkbox only works when one or both of the other two boxes  are ticked (Nodes or UV Grids and Intersect Lines).  The only way I could figure to hide it is to tick the "Original Surface" checkbox, which enables the material settings so that you can make its material transparent.

Hopefully this will save someone else from spending all day searching how to control node visibility.

Room Area Calculation Height

This one catches me out every time I want to change it - I have to search the internet for clues on how to control what height room area calculations are made.  This might not seem a big deal but when you have a split level building it certainly becomes vital, as room areas can be calculated for the wrong floor, or not at all.  It can also be a problem if some of your walls start or stop at unusual heights.

In this example the room on the left displays its hatching and area correctly.  The one on the right does not - the difference here is that one of the walls on the right has a base offset of 200mm.  By default the room area calculation is done at zero height above the floor level, so Revit considers the room to be not enclosed.

How do you change this?  After much head-scratching you might eventually figure out that the setting is not a project setting, nor a room setting but is in fact a property of the Level that the room is placed on.  If you go to a section or elevation view and select the level, it will display the properties.

One of the properties is "Computation Height".   Change the value of this to 300mm (above the base offset of the wall), and the room is now enclosed properly.

Pretty obscure huh?  You can argue whether this is the right way to control the area calculation as it certainly gives flexibility to have different values for each level.
But there is no doubting that this has to be one of the most hidden away settings in Revit - who would think to look there?  Who would remember this setting without being traumatised by spending hours or days trying to troubleshoot why a room is not properly enclosed?