Get exterior face of a wall

Hi, this topic isn’t new…
Kulkul answered this question in

but i don’t understand why he gets 8 exterior wall faces…
I only need the 4 exterior wall faces. How do i get them?

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I’m afraid this method actually filters all the vertical faces, which includes the interior faces and also the small faces from the thickness of the wall.
One way to filter only the exterior faces would be something like this:

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Viktor, this looks good. Thx.
Is it possible to get the exterior faces without the gap at the corners?

Well this could be one way:

Although I have a feeling that it might not be the smartest way.

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Yes, this could be a way, but only if the walls are in a rectangle shape.
If there are more than 4 corners this would not work.

I disagree on that point.

Ok your right! thx for help

It worked for me. But now i have a following question.
I want to get the intersection line from every surface with the xy-plane at z=0.
I do this, but now i got 9 instead of 7 intersection…

What im doing wrong?

I got 3 Lines for the middle wall, because i have 2 doors:(

@Hannes Here is another possible way:


see if that topic helps:

Thx for help.
I got a solution for the problem with the doors in the walls.

  1. create boundingbox for every exterior surface
  2. get min and max from every bb
  3. get x,y for every min and max point
  4. create points
  5. create line by start and end point

Well…i still have a mistake in my programm…

Did u see what is wrong?

set the lacing of Geometry.DoesIntersect to cross product and the lacing of Flatten to longest

i did what u say…but the result is not better.
Also try set lacing of Flatten to shortest

change it to L2…but there should be 7 surface, not only 3

Well…i think there are only 3 intersections for the points and surfaces…but why? Is there something wrong with the points?

If that doesn’t work it’s a good idea to drop your files here.

ok, hear are my files…i don’t know…can’t see the mistake:(
17_04_06_1000_Forum.dyn (23.9 KB)
17_04_06_1001_Building_Forum.rvt (1.2 MB)

the point is lying on a window at some places, so it doesn’t intersect

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your are right! thx for your help.
I changed the u v point and now every surface is found.

Thx, and have a nice day:)