Objects or ‘Content’ used in BIM’s
We have grasped how the actual 3D model of a building is produced from smaller individual 3D models of each element of the building, doors, floors, walls, windows etc, etc, and that individual or manufactured products that will be used in the 3D model are known under various pseudonyms depending on the authoring software. ‘Families’ in Revit, ‘Cells’ in Bentley, ‘Objects’ in ArchiCAD and Vectorworks and that these have become generically known as ‘Content’
There are many producers of Content both within the UK and abroad. Most existing Content is Revit based and varies in quality and usability. In fact, there is a something of a ‘band wagon’ moving with a glut of large unusable files that completely miss the point of producing Content for BIM’s.
The common misconception that Content is about 3D graphic files needs to be dispelled. The only purpose for a detailed graphic file is, for architects (or other users), to produce visual information; usually elevations, sections or perspective views of exteriors or interiors of buildings, generally for presentation purposes. Complex graphic files of any product contained within a BIM serve predominantly to slow down the model and make navigating around the models slow and unwieldy. With complex and large models, navigation becomes almost impossible without splitting the model into more user friendly sub models (see more about this under Issues with BIM). This is because complex graphic files are comparatively bulky in terms of file size. Maybe insignificant in themselves, but every Kb adds up and there can be many thousands of individual items of Content within even a simple BIM. The data contained within the file, on the other hand, can be insignificant in terms of file size.
It is important therefore to understand that the predominant purpose of the BIM is to contain structured data or ‘Information’ (the ‘I’ in BIM) and in reality, much of the data or information associated with a building can be contained within remote databases or websites which can be linked back to the content. As a result, in order to keep the BIM manageable, Content files should be as small as possible. This means limiting the graphic detail to that which is required for the task in hand, and populating the Content with data appropriate to the stage of the project.
The upcoming British Standards 1192 and 8541 parts 1, 2, 3 & 4 address both the issues of Level of Detail in Content and the specific requirements for Content for Construction Product.
The other issue with Content is the exchange of content between authoring packages. Content produced in one authoring package cannot easily be imported into another without loss of functionality or data. This is a particular problem if you are a Product Manufacturer whereby you would be required to provide and maintain Content in the four main authoring or vendor formats to satisfy demand from specifiers.
There is another way of course which is where we come back to producing Content to the common standard, i.e. IFC as a Native file type (rather than as an export from one of the BIM authoring packages).
More of this in Issues with BIM.
