Monday, March 2, 2009

The Devil is in the Details

So you have this great BIM Project that has solid graphics, a respectable level of data and attributes, and all-in-all has saved you time in design. What about the drawing sheets? How much detailing work are you doing manually, and how many of your termination, intersection and other construction details are from the ACTUAL MODEL? Seems like dumping dwgs of manufacturer details onto a drawing sheet is a common practice, rather than creating the sections and drawing in the linework. Why is this? Likely it's because of the lack of detailing that is done in Families and Objects, as well as the lack of attention to materials, which ultimately drive the callouts.

The Details...

This is another issue for my style guide. Detailing associated with families should be a part of the family, so that when it is placed within a wall, the linework in section views will show up appropriately. This in itself has its pitfalls and limitations. The window goes into a wall, and has no knowledge of the type of wall, so how can the detailing be done? There are detail families which can be imported into the project file, and plunked down on the Drawing Sheets which are a good idea, since the detailing really is only important on the drawings not in the model itself... Right???... Not so fast. Yes, the detailing is only viewed on drawing sheets, but the detail should be dependant of the window, not of the wall, since the window is inserted in the wall, the wall is not placed around the window. What happens if someone wants to make a new wall section at a window... You'd need to drop in a new detail family with it as well. An instance parameter of Type - Detail Family could be nested to allow different wall type connections (Wood, Metal Concrete, CMU) to be swapped out on the fly.
I'd love to create hosted families that are more intelligent, like opening family attributes which apply to all openings of Host Type (Wall, Floor, Ceiling, Roof), so if you punch a hole in a roof, it will intuitively place base flashings, or flashing tape associated with a window. These can all be created as "Families of Type" or "Material" Instance Parameters to allow products to be swapped out without swapping out the entire family.

For instance, a window manufacturer requires that Flashing Tape be installed around their windows. If a Material Parameter named "Flashing Tape" is created within the Window Family, you can swap out the type of material by updating the material name, or importing the material from a manufacturer of Flashing tape. This works well, gets the window specified, its installation specified, and opens the door for other manufacturers to be specified alongside the window. Taking it a step further, instead of a material parameter, a Family of Type Parameter can be added to insert an entire piece of graphics and layer of information which applies to the flashing tape. Basically, create a detail family for the Flashing tape, but add the attributes and values for the product itself. Let the detail family carry information as well as graphics for a product. This allows not only a Material to be specified alongside a window, but a Product to be specified. If a competitive product wants to be specified as an equivalent, their detail family can be loaded in the window family, and voila... new options to choose from.

Now this Brings me to Materials...

Materials are the Readheaded stepchild of BIM, and it irritates me to no end. Materials are the common ground of everything built, and every material has it's specific properties that make it what it is... nobody specified "Gypsum" or "Wood". They'll specify [5/8" Type X Gypsum Wallboard meeting or exceeding ASTM Somethingorother] or [3/4" FAS American Cherry S4S] even the finish on the wood or the paint on the gypsum needs to be called out, because Someone makes that product and there are more than one set of performace characteristics for a given product. That's where inferior and superior products come from. a BIM can't calculate the VOC levels of paint if they're not listed in the material... why would anyone want the BIM to calculate VOC's of Paint??? Because it can!

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