Retain only a predefined surfaces of a closed parallelepiped

Grasshopper
1

Dear forum members,
I would appreciate some advice.

When importing .IFC files into Rhino, the glass elements of a window are usually represented as closed parallelepiped.

grafik
grafik1265×784 96.9 KB

For simulation purposes, I only need the exterior glass surface and would like to remove the remaining five faces. To avoid exploding and deleting them manually, is there an automatic method to achieve this, possibly using Grasshopper, taking into account that this needs to be done on multiple mesh elements??**

Thanks and best regards

2

Glass part looks like a box.

In case you are using Rhino 8 please share a Rhino file with a few windows.

3

Hallo Martin, yes is a closed mesh
Forum-Window.3dm (865.9 KB)

Thanks for the help

4

And you want just these faces pointing outwards, correct?

image
image2014×1540 104 KB

When you import the *.ifc, is the content a mesh or do you have the option to import the windows as blocks?

5

Right, the face pointing outwards is perfect.
Even if the windows were blocks, I would still need to explode them.

6

Yes you have to explode the blocks.

The benefit of using blocks would be that you don’t need to guess which of the faces are pointing outwards. You could simply evaluate the dot product between the normals of the mesh faces and the block plane.

The U-shaped situation could be the outside of a simple box shaped building or the inside of an O-shaped building.

7

Sorry, I didn’t understand which method you used in Rhino to automatically select the faces shown in yellow in the GIF.

8

I selected manually just to make sure these would be the faces you want.

This is how you can do it in Grasshopper.

image
image3000×718 189 KB

window-sel-outwards-face.gh (13.8 KB)

9

Thanks Martin, this help me lot.