Family Matters

It has been hypothesized (by me) that the brunt of the productivity we hit in Revit comes less from the KB reported by Windows and more from the information Revit tries to render on-screen. Re-gen is a beast. Stories are told far and wide about typing 'regen' in the AutoCAD command line and going to grab a cup of coffee, making some phone calls, heading to your daughter's recital, and watching paint dry while your state-of-the-art, AutoCAD desktop crunched the numbers. We make fun of it now and will likewise do so in the future about Revit. But what is it that is making "Revit so slow" NOW?

The Graphix

The debate rages on about the role of the GPU, Open GL, and other current gen compu-speak processes. But right now, what we know is this; the more dense your file (notice I didn't say BIGGER), the more slowly it runs. Density come in a variety of flavors, but the 2 biggest culprits are Data and Model. The "I" and "M", if you will. While data richness is my life's goal and shouldn't be reduced, the Model can (and should) be. One of the the easiest way to control the Model is through the...wait for it...families. Before you think it, this is not a discussion of 2D vs 3D (in my opinion, there is no discussion, but more on that later), but a discussion on View Frugality. That is, showing what is important to you and not showing what's not. While a complex, fully realized 3D family can bulk up your KB, it doesn't have to muck up your view render time. Through a couple of responsible family creation maneuvers, you can have the leanest, meanest, Chuck Norris-est project on the block.


Visibility, Detail Levels, and Symbolic lines...Oh MY!

Long story short...

1. ALL forms to be turned off in Plan/RCP (maybe Front/Back. Left/Right, if your elevations are giving you fits too)


2. The most highly detailed bits (nuts, bolts, washers...j/k) should be set to Fine ONLY!


3. Symbolic Line representation of the family.

What Revit can't see, Revit can't generate. Problem solved.

So stop all this worrying about file size, and focus on better creation. 2D vs 3D is another Red herring. The most highly detailed model and the most generic family of lines are separated by but a few hundred KB. Building Responsible Familes is everyone's responsibility.

Lazy Parsing

When is the right time to break a single model in multiple models?

That is the $25,000 question, isn't it? Do you rely completely on Windows to tell you the size of our Revit database? If so, what size are you afraid of? How is the database compressed?

Most BIMs start as a singe file. Sometimes, you are asked to split out certain parts of our building for others to access (read: structure, medical equipment, etc). But what about the architect's model? You all know by now that there is a connection between the compressed database size (what Windows reports) and the physical memory we have available. You have perfected the 3G switch and maxed out your MoBo with 4gb of the fastest RAM. You have heard and are applying the 10:1 rule (or [10:1]x2 depending on who you ask). You have all increased your virtual memory to be twice the size of our physical. But, with all that in place, what then is the ceiling? What about compresing the file or even re-creating the central file? Sure, your number will drop significantly, but then balloon back up within days. Can you really trust that number?



The obvious answer (which is not an answer at all) is "maybe". Quite honestly, it's the only number we have to go on. There are, however, other things to be considered. How much detail is Revit trying to render onscreen at a time? Is Revit trying to render and\or hide every face of the every family, or have the 3D forms been hidden in plan, leaving the Symbolic lines to represent? How many families are loaded, but unused. Extraneous views, anyone? Embedded jpgs, or, say it ain't so, exploded ACAD! NOOOOOOOOO!!!!! What about other software running at the same time (FOR SHAME!) "File size" is not the only determinate factor in breaking a BIM apart. It is a bit of a red herring. Only through responsible model building and family creation can better performance be achieved. We must all do our part. Tune in later for a look at "Building Responsible Families", where I will try and dissect the family creation process into it's major functional uses, and assess how far is too far enough.

Otherwise, "split the model up when you need to". Unfortunately, there is no magic number.