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enter image description here

1.Any idea how to filter red faces from model?

2.Below is my settings

3.Example without GN from which I want to filter modules enter image description here

enter image description here

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  • $\begingroup$ go into edit mode and hover over any red face and press L then on the lower left corner select by material. $\endgroup$ Jul 4, 2023 at 12:05
  • $\begingroup$ Sorry but in geometry nodes its made proceduraly so I need to make subdivision on the red faces $\endgroup$
    – Mateusz 88
    Jul 4, 2023 at 12:06
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    $\begingroup$ please provide your node tree (or better: a blend file), because the solution depends on that! we have no idea how you did that. $\endgroup$
    – Chris
    Jul 4, 2023 at 13:05
  • $\begingroup$ oh i didnt read the title lol $\endgroup$ Jul 4, 2023 at 13:29
  • $\begingroup$ It's still unclear what you mean. It's not clear what the last image represents. Based on title I would think you want to get all the external vertical faces as in Chrises answer. But then you mention the color of the faces and in your .blend file you have orientation display enabled, which makes some internal faces red. $\endgroup$ Jul 4, 2023 at 17:42

2 Answers 2

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unfortunately you didn't show us your geometry nodes tree, so we have no idea how you did it.

So i assume you will say: but i have another node tree, it doesn't work. Then my answer will be: so please improve your question and provide your node tree.

and yes, my answer is on your title: how to filter border faces.

Anyway...here is a solution, how you can create such a grid and select the outer faces:

enter image description here


update for your provided blend file:

unfortunately i am still no sure how your end result should look like, so hopefully you want this?

enter image description here

enter image description here

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  • $\begingroup$ Hi, It works (partialy faces on my example are fliped) My setting is different I'm trying to make puzzle modules based from subdivide plane. Different materials will spawn different buildings. Please see my GN. $\endgroup$
    – Mateusz 88
    Jul 4, 2023 at 15:50
  • $\begingroup$ hi Mateusz....i will have a look at it, if you provide your blend file, but i am too lazy now to rebuild yours - sorry. I wasted my time already because you didn't provide enough information. And you want help from us in our free time, right? so pls make it easy for us to help you. $\endgroup$
    – Chris
    Jul 4, 2023 at 16:53
  • $\begingroup$ Hi Chris I appreciate Your time. File is uploaded so If You have time please look at it... Thanks $\endgroup$
    – Mateusz 88
    Jul 4, 2023 at 17:22
  • $\begingroup$ i updated my answer. Please be careful when redoing node trees. My solution had set the sample index to edge - yours was on points. But now i saw your node tree, i set the separate geometry to face and the sample index to point. $\endgroup$
    – Chris
    Jul 5, 2023 at 8:01
  • $\begingroup$ Works, Thank You for solution. $\endgroup$
    – Mateusz 88
    Jul 7, 2023 at 17:21
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This solution is in case you really have a certain material on those faces. If you do not have such special indicator for what you want to select, then it depends on what nodetree you use to create those faces. One way would be Chris' answer. But just for completeness, in this answer let us assume you have faces with a certain material on it and want to select those.

Let's say I have a cube. Most faces have a red or green material. The face on top has a blue material:

base cube

If I would now want to select the blue face in Geometry Nodes for example to delete it, I can do this with a Material Selection node where I choose the blue material and use the Selection output for the Selection of a Delete Geometry node (make sure the Delete Geometry is set to Face):

delete faces with blue material

Note: I have done this in latest officially released Blender version 3.6.0, the Material Selection was in 3.5.1 as well but I don't know when it was introduced.

If instead of deleting the blue face this is the only one you want to keep, you can invert the selection with a Boolean Math node set to Not:

delete all other faces

Other Boolean operations are of course possible, too. Maybe you have five materials and want to delete two of them, you can combine the two material selections with a Boolean And node for example.

Whatever you want to do with the selection instead of deleting faces, the Material Selection node is the one to get this selection.

Another way to do it: The next cube has a blue face on top and a blue face to the right. I want to delete the blue face to the right, but keep the one on top. You could do this by creating two identically looking blue materials and putting them on the different faces. But this is not very comfortable if you want to do changes in the material later, you would always have to change both.

What you can do instead is put two material slots on the object with the same material, and assign the different slots to the different faces.

multiple slots

Now you don't use a Material Selection node, but a Material Index node and with a Compare node you check if a material has the index (= slot) of the face material you want to delete, in this case index 2:

delete by index

Of course you can also invert this by using Not Equal or maybe choosing every material with an index > 1 to delete the second blue and the green etc.

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  • $\begingroup$ i think he wants to filter border faces, not by color, as the title says ;) but i might be wrong... $\endgroup$
    – Chris
    Jul 4, 2023 at 13:07
  • $\begingroup$ Maybe - but then this answer might be helpful to others who want to filter by material :D I actually edit another additional material approach into the answer. $\endgroup$ Jul 4, 2023 at 13:16
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    $\begingroup$ Note: The node Material Selection is available since v3.0: blender.stackexchange.com/questions/273541/… $\endgroup$
    – quellenform
    Jul 4, 2023 at 13:51

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