Monday, 18 June 2018

Extrusion Offset properties in Revit CME

Following on from the description of creating extrusions in the Conceptual Massing Environment, here is another subtlety regarding properties of extrusions in the CME.

Offset Properties 

Locked extrusions have 'Positive & Negative Offset' properties, that drive the distance of the end facets from the original profile.  These behave in different ways depending on exactly how the extrusion was created and locked.

Reference Line Extrusions

  • Create Form using reference lines as the profile
  • Creates an extrusion, which is automatically locked
  • The form has Positive and Negative Offsets, relative to the reference lines

  • Select the base facet, drag down

  • Negative offset value
  • Reference lines remain in original position

  • Unlock the extrusion - no offset properties

Model Line Extrusion

  • Create Form using model lines as the profile
  • Extrusion is not locked  automatically
  • Does not have offsets

  • Select the top facet
  • Lock the form to an extrusion
  • Padlock does not appear (unless you reselect the form)
  • It now has Offsets, relative to top facet (not the base, which was the original profile)
  • Drag the top facet up and it shows a positive offset
  • The Negative Offset is the position of the bottom facet relative to the original position of the top when it was locked - there is no visible record of that location.
  • Undo
  • Edit profile
  • It does not ask you which profile to edit (as it is locked)
  • Revit goes into Sketch edit of the top facet (not the base, which was the original profile)

  • Cancel
  • If you were to 'Dissolve' the form at this stage, you would end up with only the top facet, which is in a different location to the original profile.
  • Do not proceed with 'Dissolve'; or Undo, if you did.
  •  Unlock the extrusion form (the Offset properties disappear)
  • This time, select the bottom facet (or a line/edge on it)

  • Lock Form
  • Offsets now relate to bottom facet - more logical in this situation

  • Edit Profile
  • Sketch edit is now the bottom facet (original model line profile)

The moral of this tale is that you need to plan very carefully when creating extrusions - first choose whether to use model or reference lines;  If you chose model lines (which allow easy editing of the profile to add/remove segments) then choose a line/edge carefully before locking the profiles.


A real life example of when this would be important is the creation of a 'context' model for your site:
You want to model adjacent buildings as simple extrusions, and you want to control their height by typing in known RLs, without having to calculate heights.
  • As you probably want to work in context in a project, you might create an in-place mass family;
  • However, it could also be done in an external family, as a generic Adaptive Component (with no adaptive points), changed to a site category;
  • Draw the profiles on a Datum level (or reference plane) at RL zero (or round number, say 100 or 1000 metres)
  • Choose model lines for easy profile editing (or reference lines for stability);
  • Create Form
  • Deselect the top facet
  • Select a line on the base
  • Lock Profiles
  • Select the top facet
  • Type in the RL (in mm) for the building height

  • You could also adjust the base facet height using a minus value in the negative Offset property to represent the RL of the base of the building

Monday, 11 June 2018

Creating Extrusions in Revit Mass - CME Part 1

The previous post introduced the idea of comparing the five traditional form creation tools with equivalent techniques in the Revit Conceptual Massing Environment.  Here we analyse the subtleties of creating forms in the CME.

Part 1:  Extrusions

It might seem to be pretty straight forward creating an extrusion in the massing environment, but it is surprising how many tricks there are to it.  These depend largely on how the profile is created before using it to generate a form.

I have recorded a video description of this process, available on YouTube.

This one is pretty quiet, maybe suitable for an open plan office.

For those who prefer a more old fashioned UX, read on . . .


  • Create a 2d profile (model lines, reference lines, loaded component or select edges of an existing form). NB. The profile cannot contain a loop within a loop
  • Select the profile lines
  • Click on Create Form
  • It will create a solid if the profile was closed, or just some surfaces if it was open 

Model Line Profile

  • If the profile was made from model lines, you need to click on ‘Lock Profile’ – this will ensure that the form remains as an extrusion.
  • You will not be able to add a profile (icon greyed out) 
  • You will be able to add an edge to the sides of the form (perpendicular to the original profile), but not to the ends (parallel to the profile)
  • If you add an edge it changes the shape of the whole extrusion

  • The ‘Edit Profile’ icon will become available – this takes you into a sketch mode for editing the profile like the traditional method; you can add/remove segments from the profile
  • NB. The sketch will be top or bottom depending on which part of the form was selected when it was locked - watch out for this when locking the extrusion.

Reference Lines Profile 

  • If the profile was made from Reference lines, you get an option to create a flat surface or a solid extrusion (unlike a model line profile which only allows solid forms)
  • The profile will already be locked after creating the extrusion;
  • You will not be able to add edges to the form even though the icon is available;
  • You will not be able to add profiles to the form (icon greyed out); 
  • The ‘Edit Profile’ icon will be greyed out so you cannot edit by sketch;
  • You can manipulate the profile by moving the reference lines (limited edit); 
  • If you delete a reference line, the form loses that side face and ends – leaving it as a series of surfaces

  • You cannot add reference lines;  if you try to add a radius to a corner for example, it just breaks the form;

Component Profile

  •  If the profile was made from a loaded component, the profile will already be locked after creating the extrusion;
  • You can manipulate the form by changing the profile parameters;
  • You can sometimes modify the form by reloading an edited version of the profile - it depends on how radical the changes are as to whether it works.

Extrusion Properties

Locked extrusions have 'Offset Properties'.  These behave in different ways depending on exactly how the extrusion was created.  More details in another blog post. . . .

Unlock an Extrusion

Extrusions created from any kind of profile can be unlocked.  Once you do this they have the potential to become some other kind of form, as soon as you make any further changes.  Refer to the other form creation methods for more detail . . . . To be continued

Saturday, 2 June 2018

Creating Traditional Revit Forms in the Conceptual Massing Environment

In my recent presentation at BILT ANZ 2018 in Brisbane - Creating Nurby Forms in Revit, I started off by analysing how the traditional Revit 3D form creation tools can be matched in the Conceptual Massing Environment.

Extrusion in CME

Traditional 3D form creation in Revit has 5 predefined sketch-based tools – these are well understood by most Revit users. They are also very limited when it comes to creating double-curved or organic shapes.

Unlike these, the newer Adaptive/CME form creation methods (from Revit 2010 onwards) are somewhat of a mystery to many users – the logic is completely different, and there is only one ‘Create Form’ command.   However, it is capable of creating much more organic shapes than the traditional tools.

I have previously listed an extensive comparison between the 'Rival Revit Form Creation Environments'.  In this series of blog posts I will go into much greater detail on the subtle inconsistencies between each form creation method.  Understanding these 'exceptions to the rule' make the whole Conceptual Massing Environment (CME) much easier to work with - I use the word 'easier' rather than 'easy', because the CME is never easy!!

One of the big differences between the old and new methods is the ability to ‘Loft’ shapes in the CME, or to use multiple profiles in a swept blend:
  • The traditional environment allows the creation of a ‘Swept Blend’, which creates a single transition from one 2D profile to another – while this does allow some double curved surfaces, the transition between the two is constant along the path of the swept blend;
  • The CME also allows the creation of a Swept Blend along a path, but the big difference is that it allows more than two profiles – this allows the transition to be controlled and changed at any point along its path. There are many ways to achieve this but unfortunately Revit has a number of significant limitations in what kinds of forms it will create (more on this later).
  • The CME ‘Loft’ function allows the use of multiple shapes/profiles to control the transition from first to last, without selecting a path.
 There are many more differences that will be described in the following posts.

CME shape creation methods

The CME Create Form function only has one icon, with no user controlled options - and it works in several different ways, depending on what elements you select:
  • Single shape/profile (chain of arcs/lines/curves) – creates an extrusion of the profile. It can be an open profile that creates a surface, or a closed profile that creates a solid form, in which case it puts end surfaces on the extruded form
  • One profile plus a path - creates an extrusion or sweep (can be multiple segment path for closed profiles) 
  • One profile plus a separate straight line - creates a revolve
  • Multiple profiles plus path – creates a swept blend (single element path only)
  • Multiple profiles without path – creates a loft form
  • By hosting elements along a path then selecting all the elements (but not the path) – it creates a hybrid swept blend / loft 
It is not clear to the user how Revit decides which creation method to use and how it decides which element defines a profile, and which is a path or axis, nor the order of multiple profiles.  This is the crux of the problem - in simplifying the User Interface to a single command icon, Autodesk have robbed the users of predictability and real control over the end result.

Some of the problems could be alleviated by the following two capabilities - please vote for them on the Revit Ideas wish-list if you agree:

Control profile order during form creation

Nominate Path during form creation

Traditional Methods in the CME

Each of the traditional form creation methods (plus lofting) are examined in the Conceptual Massing Environment in the following blog posts (links will be enabled as each is posted):
  1. Extrusion
  2. Blend
  3. Revolve
  4. Sweep
  5. Swept Blend
  6. Loft
  7. Hybrid Swept Blend / Loft


The form creation path (if used) can be model or reference lines or edges of another form or component
  • Path can be a single arc, line or curve (Revit help refers to all of these as a line)
  • Sometimes it can be a multiple chain of elements – for closed profiles on sweeps only
  • It cannot be a ‘divided path’ element


The form creation profiles can be:
  • Model or reference lines (chained) or 
  • Edges of a form or 
  • Loaded components - 2D model lines (planar) within a component (adaptive or traditional of most categories, but not a traditional 2D profile family)
  • Must be a single chain of lines, arcs, curves (open or closed profile);
  • Very occasionally Revit allows a loop within a loop;
Depending on the original profile, the form behaves quite differently - It makes a big difference whether you use Model lines or Reference lines:
  • Model lines are ‘consumed’ by the form and can be edited later (Edit Profile);
  • Reference lines are retained as an underlying rig for the form – and they can be independently edited to change the form (can only be moved/stretched);
  • Reference line extrusion forms are automatically locked; model line extrusion forms are not;
  • Component profiles are not consumed, and can be changed if parametric;
If you host points onto a path, and then host profiles on those points (as recommended by Autodesk), there are differences in behaviour once a form is created from the profiles:
  • Model line profiles – the host point gets consumed too. It cannot be selected or moved; it loses any properties & associations to parameters (eg. for offset from end of host path); to move the profile along the path, you have to select it, not the host point – which has no parametric control;
  • Reference lines – the host point retains all its properties and associations, so it can be moved along the path parametrically (profile goes with it)

There are other subtle differences, to be explained later - in the individual form creation method posts.

Adaptive components 

Adaptive Components are a special kind of Revit family that operate in the CME world (not traditional family editor forms)
  • They are similar to Mass families but can have multiple insertion points
  • They can be of some different categories (but not mass) – somewhat limited
  • Cannot be created in-place in a project


Repeaters are a kind of array, in the CME world
  • Made up of adaptive components hosted on divided paths or surfaces within a mass or adaptive family, which are then arrayed using the ‘Repeater’ function.
  • Profiles within the repeaters can be used to create forms, with some limitations – the Repeater first has to be dissolved; the divided path cannot be used as a form creation path.

Sunday, 20 May 2018

Revit Ideas Wishlist Voting

Autodesk created the 'Revit Ideas Wishlist' a while back - yes I know it is flawed and has a lot of rubbish on it.  However, I know that the Revit Product Managers do actually look at it and monitor the votes.  It is not the only thing that decides what goes into future Revit upgrades but it contributes to the discussion - so I like to support it, in particular the sensible ideas that are posted on it.

I do believe that we should mainly be voting for things to be done to the core software that cannot be done by API, Dynamo or Add-ins - as those things can be done quickly by others (or yourselves).

Here are some of the better ones that I think should be voted up (including some that I have posted):

Please go to the Revit Ideas forum and vote for any of these ideas that you agree with:

Model Stability (& Pins)

Allow us to change 2D extents of pinned sections - just like we can for grids and levels.  Then we could leave those sections pinned all the time and not risk losing attached annotation.

Persistent Pins - pins that reinstate themselves after you have modified the element once


#1 wish regarding parameters is to allow Shared Parameters in Key Schedules  - this would unlock so much potential in Revit, and the API just can't get in there to solve it.

There are several outstanding Global parameter requirements:

The first is oh so simple, but would be a huge deal for us:
Enable global parameters to associate to Floor ‘Height Offset from Level’ system property

Enable global parameters to associate to Array Numbers

Enable creation of an Area Reporting Parameter for use in Global Parameters

For more detail  refer to Global Parameter wishes

Stairs & Railings

There are so many things that need to be fixed on stairs and railings, that I have created a list of requests just for Stairs and Railings.

There are a couple of basic ones that just need to be done to improve stair arrows - not much more than bug fixes:



Are you intensely irritated by the default setting for face-based family placement being 'Place on Vertical Face'?  I think that 99+% of users would like it to be changed (not to mention BIM managers who have to deal with confused users not understanding why they can't place ceiling fittings).
Vote her to  make the default 'Place on Face'


Form Creation

Creating forms in the Conceptual Massing Environment is fraught with problems - some of them could be alleviated by the following two capabilities:

Control profile order during form creation

Select Path during form creation

There are oh so many more things that need to be fixed in Revit - but since Autodesk concentrate on such a few, we need to target which ones would genuinely benefit the most people.  And we shouldn't ask Autodesk to spend time on things that can be done by some other means (API, Dynamo etc).

Have a look at the latest updates to the Autodesk Revit development roadmap to see what is planned or has been recently delivered.