Wednesday, September 30, 2009

Invisible to be Visible?

This is what I would I consider to be an "old technique" but it has come up recently around the firm. How to make objects that are above the view's cut plane (in plan) visible (I suppose it might work in section/elevation, but I never tried).

If you've read the wonderful Revit series "Introduction to Revit Arch" & "Mastering Revit Arch" (both solid books, thanks to the authors, whom I've been meaning to blog about), you should already know that certain objects will show-up, even if they are above the cut plane of the view. All of the categories are categories that are "cut" in plan and it mostly has to do with architectural convention about showing some stuff in a plan, even if it is not "technically" visible in the plan.

So that works really great, for those categories. However, what if you have a light fixture (say a wall sconce) that you also want to show in your plan, but of course it is mounted at 5'-6" or 6'-0", what do you do! Even if you put in symbolic geometry it won't help, as the view is not cutting the object, or the object is not below the cut plane. One solution would be a plan region, but they can be wonky at best, and would you really want to do a plan region for every wall sconce...? Or meven worse, modify the cut plane for the whole view? More then one view ! What we really need, is way to convince Revit that it is "cutting" through the object, even when its not.

Enter the Invisible line, an unseen friend! Take your wall sconce family, and you'll note that among the various Line Types (really subcategories) available to you with which to draw lines is "". Now, simply draw a line from the reference level to your wall sconce geometry (you can do some align/locks if you so choose). Pop the family back into your project, and viola! You're sconce will show up in your plan, with no extra effort.

Now wait! You might say, what is going on. Quite simply Revit is obeying its own rules (kinda like Kirk in the Kobayashi Maru, but not really), while we can not "see" the invisible line, when Revit's view cuts through the line, its there, and it "sees" it, which means it sees the object. Since a light fixture is a "non-cuttable" category, that means Revit must render the fixture in projection, since this is a plan, that means to render the light fixture in projection would require that the "top" of the fixture be shown in the view. Therefore, the light fixture is displayed in plan the way you want it to, all because of a simple invisible line.

I've not done an exhaustive review, but I beleive invisible lines are only availble in families that belong to categories that do not cut (which would make sense), I'm also not sure if the line style shows up if you make a family first with a generic template, then change the category. I'll leave it up to you the reader to explore and learn on your own. I do know it works for light fixtures and speciality equipment (the two I deal with most often, and where the issue is most likely to crop up).

Friday, September 25, 2009

Classic Roman Architecture anyone...?

This started as a little "show & tell" to Zach, and now its a movie... (mine didn't work nearly as well as his).

I think this goes further to suggust what you can do with these tools to handle complex geometry we just could not model before. Easy? No! Cool? Yes!

Further disclaimer - Zach made the video, not me. I just got the conversation started..... (my panel didn't work nearly as well as his)

Thursday, September 24, 2009

When E is not... E?

I was working on a family here at the company, and it turned out we need to use a formula that involved using a Log function (you remember Calculus right? Cause I don't.....). In excel the Natural Log (that is the log taken of e, your handy dandy mathematical constant) is notated with the function ln(). Which is fine and dandy. If you look in Revit help under valid syntax, is conveniently says that the "log" can be taken of any number, what they fail to mention is the base the Revit log function operates in, which is 10, not e (bummer :( )

But....! If you do enough research (or remember enough Calculus) you find out that Logs in base 10, can be converted to Logs in another base, by some simple alegabra. (hooray!) Even better, Revit help clearly states that the function exp() will raise e to the specified power, so therefore we could write:

= log()/log(exp(1))

and we would get the result we need, since a number raised to the power of 1, will simply be the original number. This is good, because theoretically this means that Revit (and or your computer) will use e calculated to the most accurate value the program (Revit) will accept (you're still with me, right?).

Yet, for some reason, Revit's result did not agree with Excel . With a little more help from some friends (read the whole AUGI thread here) it was discovered that the function exp() resulted not in raising e to the specified power, but 10!!! So, exp(1) = 10 in Revit, contradicting Revit's own help documenation!

Now I ask, why would we ever need a function that raises 10 to a power? I can always write: 10^2, 10^2..... I can even use parameters for both values if I need to, 10 is a number, not too hard to deal with. I would much rather have access to e particularly since I need it!

For now, we're using a truncated value for e in our formula, and its close enough, but I would say, with relative certainty that somewhere (quite a long time ago) someone made a mistake...

Not that too many people are running around using Logs and e in their Revit formulas, but with the advent of the new massing tools, it could become a possibilty. Besides, its the principal of the matter, right, we should have access to our standard mathematical functions, and the documentation should be correct!

Tuesday, September 22, 2009

Streaming Revit!?

Autodesk Labs has come out with something new and interesting. The ability to test drive and stream apps from their servers:

Project Twitch

This is really interesting to me, as it means that potentially we could do something very similiar internally, or, eventually, like many "cloud computing" applications, we need only pay for how much access we require to applications like Revit, Maya, Autocad, and our IT deptartment does not have to worry about maintaing the high powered comptuers or software.

Now, I realize that likely in the short to medium term server side apps will not replace the functionality of having something like Revit or Maya local on your computer, however, with a decreasing need for 2D Autocad, I could see high value in being able to "buy direct" from Autodesk, how much, and when we need access.

Wednesday, September 16, 2009

The future really is coming...

Steve Stafford recently had a really good post about "the future" here is another.

Indiana University has released BIM standards for project delivery, to be followed by BIM contracts. They cite a number of sources I'm familiar with, including the State of Wisconsin, which has also released BIM standards.

These standards are real, and they're detailed. Generally I don't take much issue with them, and most of them assume you're working Revit. However, I did note in IU's standards they require all wall finishes and materials to be included... paint anyone? It will be interesting to see how all this plays out. I have to assume that any of these organizations are willing to negotiate once you get to the table, since most of them require some sort of "plan" with regards to how the design team and contractors will work together, and the required model deliverables.

Tuesday, September 15, 2009


We apologize for the lack of posting recently. For those who don't know .... you guessed it ......


Some of you who come to Boston RUG meetings will know this but we've moved to Boston!

And in case you didn't know this is Robert's wife Krista posting because I got tired of waiting for him to "get around to it". Thanks for the patience and we hope to get back to our regularly scheduled Revit posting soon.