Cut with Voids when Loaded in Revit

When this new feature appeared in Revit about 10 years ago (v2012?), it was always a bit mysterious - it had many confusing restrictions about how and when you could use it

So, what is this family property that shows up in the Family Editor in Revit?

Autodesk Help in v2021:

Autodesk Help

"Cut with Voids When Loaded: When selected, voids created in the family will cut through solids. The following categories can be cut by voids: ceilings, floors, generic models, roofs, structural columns, structural foundations, structural framing, and walls."

That's it - all the help you will get from Autodesk on this one!  It hardly explains much about how to use it.  If you dig deep you might find more information - but there is no link to it.  

It is inaccurate in that it says "voids . . . will cut through solids".  It should say "may cut. . . "
It is also not up to date with its category list.

In Revit the tool-tip is pretty much the same, although it does at least have a diagram that shows why you might want to use it:

This is a classic example of inconsistency in help and tooltips.  I remember during beta testing that we asked for the ability to cut holes in worktops using this new feature - worktops are usually in the "Casework" category, which was not included in the list of cuttable categories.  Luckily it was added as a further enhancement a year or two later - but Casework does not appear in any lists from Autodesk, even though it was used in this illustration.

[Edit] If you dig deeper in the Autodesk Help files under 'Cut Geometry' , it does have an updated list of categories that can be cut by this method:

 "You can cut objects in a project when a family with unattached voids is loaded.

Objects that can be cut include: Walls, Floors, Roofs, Ceilings, and Structural Framing, Structural Columns, Structural Foundations, Casework, Furniture, Specialty Equipment, and Generic Models."

I recently had a requirement to use this "new" feature in a Revit family - but I could not get it to work.  So I decided to revisit exactly how to make it work:

How does it work?

• A void form has to be created in a Revit family

• Tick the "Cut with Voids When Loaded" checkbox in the family parameters
• The category of the family is not relevant to this feature
  

• Load the family into a project

• Place the family in the project in a location where the void intersects with an element in the model

 

• The element will not be automatically cut

• Use the "Cut Geometry" command

• Select the element to be cut, then the family with the void in it

 

• The element may or may not be cut, depending on the following rules:

Rules and Exceptions

• The element to be cut must be of one of the following categories:

• Casework (not listed in the help file or tooltip),
• Ceilings, 
• Floors, 
• Furniture (not listed in the help file or tooltip),
  
• Generic models, 
• Roofs,
• Specialty Equipment (not listed in the help file or tooltip),
  
• Structural columns, 
• Structural foundations, 
• Structural framing,
• Walls

• The void in the family must not be cutting anything in the family - this is the rule that caught me out recently.  To get around it I had to create two voids:

• The first one to cut elements in the family
• The second one to cut elements in the project 
• [Edit]There are two ways to prevent the void from cutting elements in the family:
• 1. You have to create the void in a location where it does not intersect any geometry,
• then move it to the correct location - it will not cut any intersecting geometry;
• 2.  Or create a solid where you want it, and change it to a void - it won't cut unless you tell it to [Thanks to Simon Weel for reminding me of this method]
  

 

• [Edit] I have had problems with saving families that only contain a void element that is not cutting anything - but I think that only happens for in-place families.

• Cutting only happens in a project

• This capability does not work in the family editor - when one (cutting) family is nested into another family.  This is a very frustrating restriction - it means that you have to build additional voids into the parent family, which is a pain if you have complex angled geometry.
  

Once you understand those rules and limitations, you can use this capability to get families to selectively cut elements in a project.  It does have some advantages over 'Face-Based' families that also allow you to cut into a host element:

• You can decide whether you want individual elements to be cut or not
• It does not need to be hosted  - it can be placed directly in the model with its own parametric controls (height etc)
• It can be moved away from or to an element to be cut (it remembers the cutting status if moved away and back)
  
• This can be added to existing families (converting to face-based requires recreating families)
• The void can be anywhere in the family - it does not have to be related to a host face in the family (as face-based families do)
  

I hope this saves time for anyone who cannot get this feature to work properly.  

In this example I have carefully made the void slightly bigger than the basin for clarity in the illustrations - and to make sure that water runs down the side of the basin into the casework and rots the timber.  I suggest that you make it a closer fit or use lots of silicon to seal it.

System Volume Parameter in Generic Category Families

 Here in New South Wales, Australia, we have a planning requirement (SEPP65) to provide a certain amount of storage in multi-unit residential developments.  Some of that storage can be in the apartment itself, and some can be in storage cages/cupboards in the basement.

The storage has to be calculated by volume per apartment - this means that we have to create schedules that combine the storage cupboards in apartments with the cages in the basement.  Thus we need to create objects of different shapes and sizes in the model.

There are several ways to calculate the volumes from these objects, but surely the simplest way would be to use Revit's automatic volume calculation properties?

System Volume Property

You would think that Revit would be able to report back the volume of any object in your model.  It is a database, right?

It turns out that it can do so, to a very limited extent - and of course that leads to restrictions and frustrations.

It seems that only cetain category objects can report their volume, and then there may be further restrictions on scheduling or tagging:

By Category

• Many of the system families do have a "Volume" property

• But you would not want to create storage cages or cupboards by mis-using those categories?  No, you would not!

• Logically you would use the Casework category for cupboards - but sadly that category does not have a volume property.
• The same applies for most loadable family categories.

• You could use the Mass category, but that is not sensible either, because that should be reserved for creating building massing models - if you start mis-using that category it will surely make life difficult (not least with visibility issues).

• Rooms do have volume properties, although that can depend on project settings - see below.
• Rooms are also not an ideal way to model such things as high-level storage cupboards!

•  That leaves us with one last option (that I know of):  the Generic category.

• For many years in Revit, generic families did report a Volume property (automatically calculated from the volume of all solid objects in the family).
• However, it was not originally possible to schedule this property

 

• In Revit 2014, Autodesk enabled the ability to schedule this Volume property.
• This was one of my few successes with lobbying Autodesk to include one small new feature in Revit, that would make a big difference to us.
• Sadly they ignored my pleas to also enable this property to be tagged.

Generic Families

Prior to v2014, we created a range of storage families that did the volume calculations as formulas within the families - so that we could schedule and tag the volumes.

When it comes to basement storage cages, the shapes often become quite complex as they have to wrap around columns or need angled sides.

This led to some quite complex formulas that needed to take into account optional cutouts to the shapes, and to allow for overlapping cutouts.

Fortunately all these calculations became redundant with v2014, as we can now use the system calculated "Volume" parameter to schedule storage volumes.

Except . . . . . When a project requires the storage to be tagged on drawings.

Room Volumes

Rooms do have the ability to calculate and report their volume, and it may be easier to create basement storage cages as rooms with cage walls to enclose them.  This would allow any shaped area without having to create a range of families.

However, this becomes problemmatic when you need to create one schedule that combines the basement storage cages (Rooms) with in apartment storage cupboards (Generic category families).

Room volume calculations also have some quirks, that depend on project-wide settings:

• Rooms have a height property - this is used for the system calculated volume.
• However, it will not work if Rooms are set to only calculate Areas (not Volume)
• This project-wide setting is generally recommended as it makes the project performance noticeably faster - the menu even tells you that (and it is true)

 

• If you enable Areas and Volume calculation you will get the volumes being reported, but a slower project.
• If you need to do this anyway, then it is no extra overhead for calculating room storage.

Room Volumes are calculated at Wall Finish, regardless of the Room Area settings.

• This can be complicated if you need room areas to be calculated to wall centrelines.
• More on this in another blog post . . . .

Architectural Ceiling Plan Hidden Categories in Revit

A while back, someone asked me why some model elements remained visible when they turned off ALL Model categories in Visibility Graphics.

The list of categories that show on the Visibility/Graphic dialog box varies depending on the Discipline filters applied to the dialog box. If you are preparing a set of architectural reflected ceiling plans, you may want to show lights, sprinklers, security etc. However, not all relevant categories are shown if you only have ‘architecture’ ticked.

Watch out for hidden categories in this situation. Each user may have different discipline filters applied on their computer (it is per user in Revit, not per view).

This means that some MEP categories may not be shown in the Visibility/Graphic list – therefore the user will not be able to show/hide or override those categories.

If the user has only the Architecture discipline showing, then clicks on ‘All’, it does not include the hidden MEP categories, including:

• Data devices
• Fire Alarm devices
• Nurse Call Devices
• Security Devices
• Sprinklers
• Telephone Devices

I have encountered situations where frustrated users have turned off all categories, and wondered why the sprinklers remain on.  For this reason I recommend that architects should consider using only  the following categories for Ceiling and Electrical fixtures in their libraries - for architectural Revit models:

• Electrical fixtures
• Lighting Fixtures
• Mechanical Equipment
• Specialty Equipment 

Architecture Discipline Only

However, for multi-disciplinary Revit models you probably need to stick with the correct categories - obviously MEP engineers should use the correct categories for their models, because they have specific behaviour that is important to them.  In the case of separate, linked MEP models, the services engineers may be modelling their own fixtures, and using the architectral model just for coordinating ceiling fixture locations.

All Disciplines

For architects working in multi-disciplinary models, where you do need to use the correct categories for all fixtures, then you need to educate your staff about changing the filter list to show all relevant disciplines. 

What a pity that we don't have all the categories that we need - Signage for example (amongst many others missing).  However we do have at least one redundant category: Roads - we'd like to be able to use it but we have no tools to model roads with.

Reveal Obstacles in Path of Travel - Revit 2020.1

Revit 2020.1 Enhancement

If you place a 'Path of Travel' using the new (in Revit 2020) feature, you may encounter a situation like that shown below, where the path appears to go through an object that should be an obstruction - such as the path through sofa example below:

 

In addition to other Revit 2020.1 enhancements to the Path of Travel feature  - Move Start/End Points, we have a new tool that may help you out:

Reveal Obstacles in Path of Travel -

This is useful for figuring out why your path of travel is not behaving as expected. 

• On the Analyze toolbar, click on 'Reveal Obstacles'

• This temporarily changes the view display to show in orange all categories that represent obstacles to the path.

In the example below (Autodesk sample file), some items are not shown orange

 

• The doors are not obstacles because that category is excluded
• Some furniture is not shown in orange (obstacle) because they are below the cut plane for calculation.  The reason is that the model is split level, and the living area is 500mm lower than the rest of the house - refer to Analysis Zone follow up for more detail on Split Levels and calculation heights.
• In the case of the large sofa family, one part of the component shows orange - this is the high back.  This demonstrates that Revit actually analyses the geometry of elements, not just a bounding box for each component - which is a good thing.

As the sofa is much lower than the main floor level, only the back projects up into the analysis zone.

• If the sofa is raised by 200mm (8"), then the sides of the sofa also project into the zone - they become obstacles, and hence turn orange (it may not be immediate - see glitches listed below).

However, the path itself does not change - you have to select it and click on 'Update Path' for that to happen;  then the path will go around the sides of the sofa.

Obstacle Settings

 

If you go the the Route Analysis Settings, you can add or remove obstacles by category - for example add Furniture and Casework categories to the list that are not obstacles

Initially nothing happens, but when you update the path it will no longer avoid those categories.  These will no longer be highlighted in orange by the 'Reveal Obstacles setting

Furniture no longer an obstacle

Casework category no longer an obstacle - path not yet updated

NB. There is some unexpected behaviour that can occur with the 'Reveal Obstacles' feature:

• If you already have 'Reveal Obstacles' mode on when you go into the 'Route Analysis' settings, then change the categories - Reveal Obstacles does not update the categories displayed orange/grey (you need to turn it off then on again for a refresh).
• If Reveal Obstacles mode is on, and you try to select an element:
• Initially it will highlight all of the obstacles as one item;  select it and you get Analysis results Properties (see below for more details)
• if you tab select, it highlights a component, but still considers it part of the analysis result;  Select it and you get Analysis Result listed but without any properties;
• Tab again and it finally selects just the element - you can then change its properties;  However, the Reveal Obstacles highlighting is not updated even when it should be - eg. if the sofa height is changed to 500mm so that the whole sofa becomes an obstacle, the sofa does not turn orange (when it should).

• If you select the whole analysis result, you get shown properties for the Analysis Result.

• It is not immediately clear what these properties are for.
• If you click on the 'Edit..' button (Results Visibility), as you would be tempted to do, you get some more mysterious properties

•  Make the dialog box a fraction wider, and one of the headings shows in full:  'Analysis Display Style' - it has a hidden button to the right of <By View>

• Click on the hidden button to reveal the Display Style dialog

• You can play around with the text and arrowhead settings

 

• And go to the Legend Tab
• Click on 'Show Legend'
• The end result means not much to me, but I'm sure it has a purpose

Arrowheads and legend displayed

•  You can move the legend on the view, if that is what you need

I am guessing that these analysis display settings are for some other kind of analysis, but have been enabled here too?

• I am not going down that rabbit hole today!

 

Conclusion

Sadly, useful as this new feature is, it does not address fundamental shortcomings - such as what you need to do when Revit fails to generate (or update) a path at all.

We need more help to be able to deal with that situation, as the Warning dialog box is not at all helpful!

Travel Path Update in Revit 2020.1

Following on from my posts about Revit 2020 on Path of Travel and Follow Up :

With the release of Revit 2020.1, we have been given four minor improvements to the new (2020) 'Path of Travel' feature in Revit.  Welcome as they are, these improvements do not address any of the fundamental shortcomings of the tool, which seems like a missed opportunity:

1. Start and End Points of travel paths can be dragged.
2. Reveal Obstacles toggle.
3. To and From Room properties have been enabled (these were previously just blank instance properties in 2020).
4. Two new Dynamo nodes for Travel Paths (presumably new API capabilities allow this?)

Start and End Points

If you select an existing 'Path of Travel' element (which behaves like a polyline detail line) it now displays a blue grip-handle dot at each end.

• Select the grip-handle and drag it to a new location - while doing so, Revit displays a moving straight line directly between the cursor and the other end of the path.

• Once you let go the grip-handle in its new location, Revit recalculates the path of travel

• Associated properties, schedules and tags will also be updated.

This is a very welcome little change to behaviour - if you tried this with the original vesion (2020), it just moved the whole path of travel.  However, this is only a small usability enhancement.

The fundamental issues it does not deal with include:

• Still no ability to choose, change or control where the actual path goes (apart from adding/removing obstacles).  In order to do this, we would need to be able to somehow nominate additional points along the path, which it must go through.
  [Edit. * NB. Revit 2020.2 improves on this]
• No ability to make the path orthogonal (in Australia I have never needed that, but comments on my last blog post indicated a requirement for this in North America)
  [Edit. * NB. Revit 2020.2 improves on this]
• No ability to deal with sloping floors, level changes (split level), stairs.
• No ability to prevent the path going through a very narrow opening (430mm or 1' 5") - more on this in another blog post.

NB. Given that the default selection colour in Revit is dark blue, and the grip-handles are mid/dark blue, it is pretty hard to even notice this new feature.  I would recommend changing your options for selection (and pre-selection) colours to something other than blue. 

Incidentally, which *!@*&#$ at Autodesk thought it was a good idea to make the selection and pre-selection colours the same (both dark blue)!

Reveal Obstacles toggle

This is a useful new tool for figuring out why your path of travel is not behaving as expected.  Again, this does not address fundamental shortcomings - such as:

• What do you need to do when Revit fails to generate (or update) a path at all.

This new feature has a few quirks in behaviour - as detailed in another blog post.


[Edit. Revit 2020.2 further improves on 2020.1]