Tuesday, February 28, 2006

BIM Interoperability - Part I

In this post we will focus on taking a simple "Building Information Model" from one software package into another. For this example we will focus on two that most people are having trouble working between; Revit Building and Architectural Desktop (ADT), in a later post we will be working with other file formats and software.

Before we jump into creating geometry we need to review a new file type that you may/not have heard about; IFC. IFC stands for Industry Foundation Classes and is a file format not created by any CAD/BIM vendor (ex. Autodesk, Graphisoft, Bentley, SketchUp, etc...) but instead is a vendor neutral format. Who is responsible for the development of the IFC? Good question, the IFC's were created by the IAI (International Alliance for Interoperability) with the goal of creating a way to exchange BIM type of data. More about the IAI mission can be found here: http://www.iai-na.org/about/mission.php

So what does this mean for those using BIM platforms? Another good question, let's start with a real scenario in which one firm who specializes in design and another that specializes in taking this data through to construction documents. This is becoming more common place as firms and companies specialize in certain niche markets. So Design Company A begins the design of a project using Revit Building. As they reach the submittal date for their portion of the project to be delivered to CD Company B who is using Architectural Desktop.

Disclaimer: Before you begin to rant and tell me how this would not happen and that company B should go ahead and use Revit to complete the project or that company A should have started this in ADT, spend a few months doing BIM consulting with large and small companies across the country and you see things in a whole new light. To clarify both Revit and ADT can create production documentation from start to finish on their own, this scenario is for those who need to blend these together.

At this point Company B has a compressed time schedule ahead of them to finish the CD set of documents. Design Company A has given them the Revit model, exported .dwg files of each sheet (including xrefs, etc...) and a hardcopy set of files. They need to start working, when you export Revit data to .dwg it is exported as simple AutoCAD geometry (lines, arcs, circles, blocks, etc...). CD Company B needs to get started right away, should they just start tracing/converting the cad geometry already provided using AEC objects?

Another approach may be to utilize IFC's. In Revit Building this can be accomplished by exporting to IFC (Ex. File>>Export>>IFC...). When exporting from Revit Building 8.1 it uses the IFC 2x2 format.

At the time of this post (Feb. 2006) the IFC format for IFC 2x Edition 3 (2x3) was just released.

From the ADT side we then need to import the IFC file. Architectural Desktop does not currently have a way built-in to import/export IFC files. To accomplish this we can use a plug-in from Inopso GmbH that will allow use to import/export IFC 2x and 2x2 format. This does have a cost associated with it and only runs on a single computer per license, but it will bring in the exported file as AEC objects.

As it stands now this method is not 100% seamless and there is some clean-up that is still needed. In the next post we will be looking at examples of this process and providing a few files for you to play with.

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