BIM Time is Here

[Bill Tillman]

I've been advising clients that sooner or later everything will be done in BIM. At least the bigger commercial projects. Well, this morning I had to watch as a client had to turn down a big contract because no one in his staff has the necessary experience to draft the shop drawings in a BIM compatible format. Okay, now the time has come when I must stop using the excuse of "someday I'll finally learn what I need to know about BIM to do it." So as I start this journey let me ask the following questions:

I've been told that BIM is total 3D. So does that mean the drawings must be produced in 3D models?

As I understand BIM, the models are produced in 3D and a datum point is used as the origin point. This data is then transmitted to the project owners and they import it into their master database. So again, it's a question of 3D or 2D.

I just read an article that you can take your 2D CAD files and using a conversion program to convert them to BIM compatible files. I'm not sure I follow this as 3D models are what the end product is. I don't see how you get a 3D model from a 2D model unless there is a lot of linking and hand holding throughout the conversion process.

IS Revit the only AutoDesk product to work with BIM. I seem to recall a tutorial I did years ago which used ACAD Architecture version. Never got to finish this tutorial so now I guess I'll have to polish it off.

[ReMark]

What is BIM? This article may be of some interest.

https://www.engineering.com/BIM/Arti...-Modeling.aspx

Another article I found interesting.

http://www.graphisoft.com/archicad/open_bim/about_bim/

AutoCAD Civil 3D is also a BIM software platform according to the above article.

[tzframpton]

Bill, BIM is a process and yes it can be 2D. It's a process of embedding information into a model. And yes, Revit is the flagship platform from Autodesk. Bentley and Bricsys, among others, have their versions as well.

[halam]

I agree with Tannar that Bim isn't invented to exclude 2d and certain software. I personally find AutoCAD (DWG if you like) better at this proces than Revit. Because it can combine more and better different sorts of *MEDIA*.(sorry Tannar) And if you like to read a good article about the function of 2d versus 3d you should read..

https://tangerinefocus.com/2017/09/0...ustrys-energy/

And what is your opinion, does the Robot in quantum mechanics have a opinion?

[lrm]

Before ever having used Revit I wondered how it was conceptually different than AutoCAD. I asked some Revit users and they could not really articulate the difference. They said “you can use a library of standard parts”. I said “well, AutoCAD can do that”. They said “Revit let’s you associate miscellaneous data with an object”. I said “well, AutoCAD can do that”. And so the conversation went without me getting a good understanding of the conceptual difference between the two products.

Here then is my brief explanation of the conceptual similarities and difference between AutoCAD and Revit for the AutoCAD user who has never used Revit.

AutoCAD, 3ds Max, and many other traditional 3D CAD systems can be thought of as having a 3D world where geometry is constructed. The 3D geometry may be composed of wires, surfaces (flat or sculptures) and solids. The user can view the 3D model from any orientation. To create an engineering drawing a particular viewing orientation is chosen (front, top, auxiliary,…) and the user adds drafting details like notes, dimension lines, and crosshatching. Additional views are made as needed to provide detail views. I call these drafting additions “cosmetic” graphics. They are not part of the nominally sized geometric model but do provide additional information to help interpret the model. AutoCAD over the years implemented various ways to address the need to make drawings from 3D models. The introduction of “paper space” and the awkward scheme of controlling object visibility via viewports was done to better enable the creation of engineering drawings from a 3D model.

Revit in contrast relies on a series of 2D models and a 3D model that are both independent and dependent on each other. Since architects and civil engineers often use plan and elevation views Revit specifically let’s you create 2D plan and elevation views (models) that are not in the same 2D/3D world of the other views. They are linked to each other behind the scene. This conceptual approach has several advantages. For example, when you look at the front view of a 3D AutoCAD model of a box each edge that you see is actually two lines, the edge in the front of the box and the edge behind it at the back of the box. Revit doesn’t have this problem. In defining standard building components such as a window in Revit you typically define a 2D plan view of the window and one or more elevation views. These are separate graphics that are imported into your Revit file when the window is inserted you’re your file. This approach plus a modern user interface makes many tasks for creating a model of a building and its drawings much easier in Revit than AutoCAD. In addition, whereas AutoCAD is a general purpose geometry modeling system Revit is targeted for buildings, bridges, and other constructed systems. Features such as reflected ceilings and an understanding of the floors of a building are an integral part of Revit. Revit is not well suited for creating a model of a complex 3D manufactured products like a valve or desktop printer.

The real “BIM” aspect of Revit is not so much this separation of drawing views but a much more sophisticated capability to associate non-geometric data (e.g., manufacturer, serial number, service schedule, etc.) with building components.

As Autodesk’s Inventor addressed the need to distinguish between drawings and models via part files, assembly files and drawing files, Revit addressed the difference between these needs for architects and civil engineers.

[tzframpton]

Before ever having used Revit I wondered how it was conceptually different than AutoCAD. I asked some Revit users and they could not really articulate the difference. They said “you can use a library of standard parts”. I said “well, AutoCAD can do that”. They said “Revit let’s you associate miscellaneous data with an object”. I said “well, AutoCAD can do that”. And so the conversation went without me getting a good understanding of the conceptual difference between the two products.

While those answers are certainly correct regarding Revit and BIM, it's not the whole picture.

When it comes to Revit, it expects - almost requires - you to plug information in. Consider the two following screenshots of information population of a fire protection pipe and a duct in Navisworks:

AutoCAD file: FP Piping
BIM-01.png

Revit File: HVAC Duct
BIM-02.png

Now, could you have AutoCAD populate all of this info in the AutoCAD file? Sure. But at what cost? And what about environmental parameters such as what level you're on (2nd floor, mezzanine, roof, etc)? You'd have to, quite literally, manually include all of this information. This is not at all a usable solution. So while you responded that "AutoCAD can do that", you're not wrong, but it's an unreasonable solution (unless of course you're using a vertical product such as ACA or AMEP).

Revit is a platform that gives you a reasonable solution to managing data from a material building perspective. Is it the best at it? Not at all, but it's a solution nonetheless.

AutoCAD gives you "Layer" and "Color" and "Material" by default, and that's about it. Revit at least gives you Categories, and at best gives you robust data managing for your own use. 3D modeling is a side bar, honestly. It's the information. To have it already there, ready to grab if you take a few minutes to add whatever data you want is invaluable and is the true selling point of BIM. I've been on the receiving end of incoming architectural and structural Revit models that are stripped of any and all documentation, and yet I still know exactly what's going on in that building, because of the information embedded into the model elements and environment.

This is my response to the "AutoCAD does that too" response. Logically, yes it can. Reasonably, no it can't.

Hope this helps.

-TZ

[halam]

Notuced you made these screenshots from Navisworks.
The conversion to nwc/nwd from either rvt or dwg only pick up certain parts. Parts of information that Autodesk want you to see in navisworks
Information you refer to is metadata that sticks to 3d forms. Dwg is just as compatible to
A. Model 3d
B. Stick metadata to it
do that as the rvt file. All autocad verticals prove it if you use Navisworks on these.

There is tons of information available if you convert these in navisworks. Not only freaking layers ;-) So there really is no real difference there. For me, still, rvt It just is being marketed as 'bim tool' for us to believe that (.. to buy)
Openbim based IFC is the closest real thing what the idea really is. But ifc development is sooooo slow.

[tzframpton]

There's "no real difference"? Can you elaborate please?

[halam]

To make that more clear, and since this forum is very much for dwg users.
I personally don't see BricsCAD Bim suite (based on dwg) any less or more capable of doing Bim than Revit, Tekla structures, ArchiCAD or Allplan.. Hell, even Sketchup can do Bim these days..

Do you?

[lrm]

tzframpton, It appears I was not clear in my post (#5) regarding the strength of Revit vs. AutoCAD for building design and documentation. I wholeheartedly agree that Revit can be the superior product in many ways for AEC applications.

What I was trying to express in the first paragraph of my post was the frustration and confusion I faced several years ago when I heard many raves for Revit but I had never used it myself. I wanted to know more about Revit but the Revit users I talked to couldn’t articulate what made it so good and how it was different from AutoCAD. The response in my post “well, AutoCAD can do that” was aimed at the non-Revit user who might be wondering how the products differ. The answer is more complex than the superficial comparison of the couple of features I was asking about. In no way was I trying to say that AutoCAD and Revit are equivalent!

Your excellent post (#6) surely address some of the differences. Your example of the information for a fire protection pipe should help the AutoCAD user who is not familiar with Revit gain a feel for one way that the two products differ. As you know, Revit is hard-wired for building design whereas AutoCAD is a general purpose CAD system and as a result the Revit user has many built-in features for building design that are not available in AutoCAD.

I found it useful to me that to understand and appreciate the uniqueness of Revit it was helpful to understand that unlike AutoCAD, Revit does not rely on a single 3D geometric model. The concept of multiple 2D plan views and 2D elevation views tied to a 3D model provide many benefits in ease-of-use and the creation of formal engineering drawings. Of course, the strong database capabilities are also key to Revit's strength. On the downside, I have found it much more challenging to create complex 3D geometry (I am an infrequent Revit user).

My comment “well, AutoCAD can do that” was my way of provoking the reader to ask “How do these products differ?” and “Is Revit something I should consider?”. It is good to see experienced BIM users on this forum detail what they think are the issues and their experience with the technology.

Lee