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).


Erik said...

Or you could just switch the view's sub-discipline to Mechanical or electrical. It will then show all Mechanical, Electrical, or Plumbing related objects that are within the boundaries of a view.
In other words, the cut plane doesn't do much in a Mechanical or Electrical view.

I'm pretty sure this works for all "flavors" of Revit.

Of course it meanes that all Architectural objects turn halftone and transparent, but hey, small price to pay. ;)

Robert said...

I have no doubt your suggestion will work, but it could cause some heartburn for the Architectural or Interior Design Project Managers... :)