Creating Blends in Revit Mass - CME Part 2

An earlier post introduced the idea of  comparing the five traditional form creation tools with equivalent techniques in the Revit Conceptual Massing Environment.  Previously we analysed the creation of extrusion forms in the CME.  Now it is the next of the 5 traditional forms:

Part 2:  Blends

In the traditional Revit environment, you have to decide on a blend before you start.  In the massing environment you can do that or decide to create a blend after you have made an extrusion.  The exact method depends 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.  Crank up the volume if you are at home.

Read on if you don't like videos (or you are hard of hearing!).

There are several ways to create a blend form in the CME:

Method A (Unlock Extrusion)

This method assumes that you already have a form created as an extrusion.

• Select the form;
• ‘Unlock Profiles’ (if locked)

 

• This converts the form into a blend, which has a profile at each end (each the same to start with) – they can be edited separately.

If the original profile was model lines:

•  Each profile can be edited in sketch mode (Edit Profile command).

 

If the profile was reference lines:

• The start remains as reference lines, with limited edit capability (move the reference lines) 
• The end profile can be edited in sketch mode

If the original profile was a component:

• you can edit the end profile only, not the start profile
• If the profile family is parametric, you can adjust the form parametrically
• You can edit the profile family, and the form changes when you reload the family - within reason; if the changes are too drastic, it may fail when you try to reload.

Method B (Create Blend)

Create two parallel 2d profiles (model, reference lines or flat components) ;

• Select both profiles; 
• ‘Create Form’

• Revit will create a Blend form

If the profiles were model lines:

• You can edit the profiles of each end 

If they were reference lines:

• You have limited edit capability (move lines)

If the original profiles were components:

• You can change them (if parametric) 

 

• Or you can edit the profile family and reload 

The two starting profiles do not need to be parallel.

Related topics:

• Introduction: the five traditional form creation methods

• Part 1: Extrusion forms

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.

Conclusion

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

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 . . .

Workflow

• 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 Blend form creation methods for more detail . . . . To be continued

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

• Blend in CME

• Revolve 

• Sweep

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 
     Extrusion Offset Properties
2.  Blend
3.  Revolve
4.  Sweep
5.  Swept Blend
6.  Loft
7.  Hybrid Swept Blend / Loft

Path

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

Profiles

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

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.