Published on CAD Semplice a blog of Domenico IEVA
BIM models are becoming increasingly common among the files designers exchange in their work.
Not everyone is ready to acquire BIM yet, because either they fail to keep pace with update processes or they are designers whose field of action does not justify the investment in BIM Authoring software. For the latter, CAD products supporting this type of file represent a great asset…
This article will demonstrate us how progeCAD 2021 can handle BIM models also offering tools to generate 2D representations from these models, such as elevations and sections. Viewing the predefined tables and creating ad hoc sections and elevations, designers can easily realize how model geometry is organized.
Furthermore, you can determine which elements to display and which to hide and that helps you reduce geometry complexity. So let’s see in detail: insertion, predefined views display, the creation of sections and elevations from a BIM model in progeCAD 2021.
Insertion of a BIM model in progeCAD
There are two modes of insertion of a BIM model into a DWG file:
The first mode is useful when you need to extract part of the building geometry present in a BIM file so that you could reuse it. 3D objects of a BIM model are therefore converted into 3D Meshes that can be managed with the corresponding commands.
The second mode allows you to link a BIM file to your DWG drawing without embedding it. It is a process similar to that of external references (XREF). The model is a single object, as if it were a block, and it is reloaded at each new opening of a drawing.
The commands for insertion are available in the group “BIM Files” on the ribbon Insert:
The progeCAD BIMIMPORT and BIMATTACH commands prompt you to specify the point where to insert your model and then the units of measurement to be represented with. It is always better to set the units you normally use rather than trust the settings saved in the file.
Managing elements visibility
Once your model is inserted, all its elements become visible on the screen.
The BIM file is not organized in Layers like a common CAD file. Choosing the Attach insertion mode, you will be able to manage the visibility of various elements of your model through the special panel which is displayed using the BIMPANE command. Hiding unnecessary objects helps you get clearer representations. To see the contents of the panel, you need first select the inserted BIM model.
If you have attached a model in the RVT file format (Revit files), the panel will consist of 3 tabs:
This tab offers a list of objects categories as they are present in Revit.
The list contains both 2D finishing objects (labels, construction lines, profiles, grids etc.) and 3D objects such as structural elements, components of engineering systems, terrain shapes, etc.
- The labels of doors, windows, plant elements have a suffix “Tags”.
- The basic two-dimensional profiles for 3D objects creation contain the word “Sketch”.
- Grids referring to columns are called “Grids”.
- Construction lines are called “Center lines”.
- Work plans are called Reference grids.
Then, passing to the elements making up a building, we have:
In the second tab, Hierarchy, the objects are organized according to the tree structure that starts from the Building and branches in various floors(Levels). In the previous picture you can see a list of 4 levels.
It is evident that, if you need to use only one floor, it will be easy to make the others invisible through this tab. Expanding the branch ‘Level’, it is possible to see what types of objects it contains and therefore to perform an even more targeted operation on their visibility.
The third tab, Views, lists views relating to floor plans, sections, elevations, views of details created by the designer in the RVT file.
In the Elevation branch we have elevations, in the Floor plans branch – floorplans, in the 3dview branch – axonometric or perspective views, in the Sections branch – sections, in the Ceiling Plans branch – plans of the suspended ceilings.
To see elevations and sections, you need to position a view perpendicular to the Z axis, then Right, Left, Front or Back.
If you have attached a model in the IFC format (a neutral exchange file format), the three tabs of the panel will display the objects with slightly different specifications compared to those that you saw with the .RVT file attached.
- Categories tab
The Categories tab lists the classes of objects according to the IFC classification, yet the concept does not change… what was earlier called “Wall”, we will find it here as “IfcWall”.
- Hierarchy tab
In this tab, the tree structure develops in Project / Site / Building nodes and then in various Levels.
- Object Properties tab
This tab shows some properties (attributes) of an element selected in the Hierarchy tab.
Make the most of Model Views
If views (plans, elevations, sections) are saved in the BIM model in the Revit format, we will be able to view the one of our interest, listed in the Views tab, double clicking on it. A new representation of the model will appear in the graphics area:
For better objects visualization, you should activate the Hidden visualization style of the window, taking into consideration they are always 3D objects.
If you need to edit the obtained representation, it is better to explode it using the Explode command. Then copy the result into a new file and, finally, go back to the previous file and undo (the Undo command) the effect of the Explode command.
There is no other way to capture a view at the moment. Unfortunately, the FLATSHOT command does not support Polyhedral Meshes resulting from the explosion of a model.
In case an IFC file is inserted, the BIMPANE panel does not show the Views tab for selection of predefined views.
We will have to compose our view by turning on and off the visibility of a series of objects.
For example: if a designer needs only to retrieve the information relating to floorplans and walls, to create executive projects or calculate individual floors, he will concentrate on the desired hierarchies and categories.
However, there is a tool that allows you to save a representation with a name and subsequently recall it.
In the upper part of the panel you can save the current view. The name “State 1” is assigned automatically to the saved view. The next saved view will be called “State 2” and so on.
The “Default” state indicates the initial state as you can see it in the animated picture below:
Also here views can be captured through exploding and copying them into another file for their further processing.
Create your own sections and elevations
If we need different sections and elevations from those present in the Views tab of the BIM panel, then we can make use of the new and powerful commands introduced in progeCAD 2021 which will allow us to generate new sections and elevations.
In the Ribbon menu “View”, there is the command group “Section Elevation”:
This group offers commands that allow you to generate Sections and Elevations from your inserted BIM model.
These specific commands recognize different object types present in a model and generate “intelligent” 2D views which remain linked to the model and so always updated.
Any changes to the BIM model, which is reloaded each time your drawing is opened, also affect your previously generated Sections and Elevations.
For the record, these 2D views are specific objects of the AECobject type that conform with the standard defined by Autodesk for its CAD software dedicated to architecture: AutoCAD Architecture.
The command SECTIONLINE allows you to generate sections of a BIM model.
The command prompts you to specify the points on the plan that define the cutting plane and then to position the section in the drawing.
The section is represented with a specific object type (AEC_2D_SECTION).
The command ELEVATIONLINE allows you to generate elevations of a BIM model. The command prompts you to specify 2 points outside the building that define the width of the view plane, then a point to position a 2D view of the elevation.
The elevation is represented with a specific object type always linked to its generating line.
As it has already been mentioned, there is always correlation between section / elevation lines and generated 2D views contained in the AEC_2D_SECTION objects.
Any changes made in plan to the section line or the elevation line may make it necessary to update the section / elevation object created previously.
To update them, you can use the 2DSECTIONRESULTREFRESH command.
Section and elevation lines are annotative objects, so their symbol size follows the current annotative scale settings. The label (“XX” by default) is an attribute that you can modify through the properties panel. You can explode the objects of section and elevation views (like blocks) if you want to edit them.
Three variables to keep in mind
Working with BIM models, take into consideration these 3 system variables which can be called up from the command line:
AECAUTOUPDATE: if it is ON, it automatically updates the views of sections and elevations when the position or shape of their respective generating lines changes. The action is triggered when you act on the Grips of these objects.
If it is OFF, the update is performed using the 2DSECTIONRESULTREFRESH command.
AECOBJECTS: the value of this variable must be 1, otherwise the views and sections commands are not activated.
IFCOSNAP: if the variable is active, it allows you to select points with osnap modes in the BIM geometry, so it is essential for measuring distances or areas.
In this regard, as we are dealing with 3D objects, it is useful to remember to set the OSNAPZ variable to 1, so as to ensure that the distance measurement takes place between points lying on the same plane.
The set of progeCAD 2021 tools presented in this article offers the first approach to files in the RVT or IFC formats. We do not deal with a simple Viewer (for this purpose there are already freeware Viewers on the Internet), but with a tool giving the possibility to explore a model, extract its parts, display predefined views, determine the visibility of individual objects… all this in the familiar environment of alternative to AutoCAD software.
According to the software developer, this set of commands for management of architectural models will be enriched in the next versions.
Many improvements could be implemented. For example, hiding of an object type selecting its geometry in the model and not searching its name in the BIMPANE panel. Let’s wait for new releases to see what they have in store for us.