Getting It All Together in 3D7 Feb, 2008 By: Scott MacKenzie
Through the use of third-party software, architects and engineers can share and view their work in a 3D model.
As you know, the AEC industry is going crazy for 3D. There are many labels for it: building information modeling (BIM), virtual building design (VBD), and 3D CAD. There is a solution out there for everyone, and because of that everyone is going to use it differently.
So what happens when you are using BIM Brand A, and your consultant is using CAD Brand B? For one thing, you will have to live with files that have been translated from a brand of software you do not have.
What happens if you want to see both brands in 3D in the same file? Well, you turn to a design review program like NavisWorks' JetStream or Ecotect to bring it all together.
I have never used Ecotect, but I am a JetStream user, and let me tell you: it is fantastic. I have been doing 3D CAD and BIM for a while now, and I still get a kick out of navigating through a JetStream model and seeing everything in 3D.
I have worked on many projects with architects, engineers, and planners. One firm does its architecture designs with ArchiCAD, and its engineering is done with Autodesk's Building Systems (now known as AutoCAD MEP).
Currently there is no prudent way to view the engineers' 3D work in ArchiCAD. They needed a way to see everyone's work in 3D, but also navigate and slice up the model in many different ways. So they chose JetStream for their 3D coordination.
Project Team Coordination Meetings
Implementing this procedure adds an additional layer to the project team's workflow, because it encourages team members to pay attention to other disciplines and their work. We used to conduct weekly MEP and architectural coordination meetings in which we all sat down and navigated through the project model. I had a great time driving the navigation while the architects and engineers pointed fingers and gave each other a hard time. It was all in the spirit of teamwork, and it brought us together. I looked forward to these meetings every week.
Setting up a JetStream project needs to be a strategic process. It is a challenge to merge AutoCAD files with the ArchiCAD models because the CAD files typically contain only one story. Therefore, each file needs to be imported separately into the JetStream model. These files should be exported to a JetStream file format, such as NWC or NWD. NWC files created from Revit or ArchiCAD typically contain all the stories in the building, so that part is easy. Shuffling all the CAD (DWG) files into the master JetStream file is more tedious.
Learning to navigate in JetStream is a valuable skill. JetStream contains several different navigation commands, and I believe new users should master three of them before making any presentations. I suggest mastering the Examine, Orbit, and Walk methods.
After you import each CAD file into JetStream, you have to override the z height to put the story at the correct height in the JetStream model. This is not difficult; just get a list of all the story heights, and override the height setting for each CAD file.
Beware of this potential problem, however: New elements in the CAD files come into the JetStream model at 0 feet high, which is most likely the wrong height. See the project setup scenarios below. The first scenario could be considered the standard, or beginner, way to deal with this (which is how I did it on my first two projects). The second is a lower maintenance scenario, but it involves more setup time.
|Scenario A can be considered the standard project setup.|
This can be an ArchiCAD or Revit project, or a true BIM software package that deals with whole buildings with multiple stories. I will use ArchiCAD as an example. The whole model building can be exported to JetStream (or 3D DWG) format, then appended to the JetStream model.
The CAD floors are 3D DWG files of individual stories. This is the traditional method in CAD with each file having a base height of 0".
In the 3D coordination model, CAD and BIM files of different formats are appended into the JetStream model. The Architectural Virtual Building model is inserted to the default of height of 0". Each one of the CAD files is inserted, but they each need to be moved to their appropriate height in the building.
This all works great until new elements are created in the CAD files. The new elements will know what height they should go to, so they show up at a height of 0". So you either need to find all the new elements in the JetStream model and transform them to the correct heights, or delete and re-append the whole CAD file for that story back into the coordination model. This can be a daunting task if you are working with a large project.
Setting Up a Project for ArchiCAD and AutoCAD
You should have the JetStream software installed on you computer in order to create JetStream file formats (NWC & NWD). I like to create NWC files from AutoCAD with the Nwcout command. I also like to use the CadFX Batch Processor program to speed up the creation of NWC files. I use the following script:
This will unload all xrefs and export the remaining drawing to an NWC file, which is a JetStream cache file. The Batch Script Processor suppresses all file dialog prompts (which is good). So the new files should go to the same folder that your open DWG files are. If you manually run the Nwcout command, it prompts you for a destination folder. But every time you use it, it defaults back to the same folder, which is the folder of the currently open AutoCAD file.
From ArchiCAD v10 you do a File / Save As and change the Files of Type: to NWC. If the NWC option is not available, you will need to have the JetStream add-on loaded. Or you can modify the JetStream installation from the Windows Control panel to accommodate ArchiCAD v10. Start / Control Panel / Add or Remove Programs / NavisWorks JetStream / Remove/Modify. Check the box next to ArchiCAD 10 and any other applications you have that are in the list.
|Scenario B is the same as Scenario A except for the way the CAD files are imported.|
MEP 3D CAD Building Model
This file has no live information. It is a conglomeration of all the CAD xrefs. Each xref is placed at its correct story height in this file, and then everything is exported to NWC. Or, you can just append the DWG into your JetStream model and the program will create its own NWC files. This takes care of the issue of new elements ending up with a height of 0" in the JetStream model.
You cannot modify size and shape of anything in JetStream, but any object in the JetStream model can be given a few individual display characteristics including color, material, and transparency. The transparency option is fabulous for using on windows. That is obvious, but it is also good for applying to walls and floors in certain situations. If you are crawling around in a ceiling plenum, you could make the ceiling partially transparent in order to see what is going on below. Keep track of the building’s story heights during the life of the project. Story heights typically will change and it is not always communicated effectively across the project team.
You may like to take some snapshots from the model and paste them on your drawing sheets. There is an issue with that because of the way the architecture displays in a wireframe model. For this you must create 3D DWG files from ArchiCAD v11, instead of a JetStream format export because the JetStream add-on for ArchiCAD v11 has not been released.
The image is cleaner with the NWC export from ArchiCAD. ArchiCAD v10 and previous versions have a JetStream add-on. Saving an ArchiCAD v11 project down to ArchiCAD v10 is not really a workable situation because of how the object libraries work between versions.
At first I assumed that because Autodesk bought NavisWorks they were no longer interested in developing an add-on for ArchiCAD v11. That is, until I heard from a reliable source something contrary. Would you want to share technical information with your biggest competitor?
About the Author: Scott MacKenzie
Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's Tips & Tricks Tuesdays free e-newsletter and we'll notify you every time a new video tip is available. All exclusively from Cadalyst!
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