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First time asking a question here ! woo. I've tried to look for an answer.. I must be missing something very basic. I started using Geometry nodes a few days ago (finally)

I'm trying to scatters stuff on instances by vertex group located on those instances

So we have those "building01" and "antenna01" objects

I scattered building01 using a vertex group on the ground plan then random rotation, all good. Now, i want to scatter those antennas on the top of those building01 instances. On the building01 object i defined a vertex group called "roof"

  • First i tried to make it all with one geometry node but i cannot access the "roof" vertex group. -I tried to stack TWO geometry nodes modifiers (one for the first scatter of building01 and a second one for antenna01). But that just... don't work. -I tried to make a geometry node for the building01 object, i can scatter antenna01 but just like shown on my screen capture all the instances are identical. Which of course makes sense...
  • Realize instances doesn't help because i can't access the vertex group on building01 anyway :(

That's it.. actually.

This is a very simple example but then i could have complex buildings bases and scatter/display stuff on them using vertex groups. like antennas on roof , pipes on wall, etc.

Thank you everyone

Blend file :

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  • $\begingroup$ welcome to SE! pls add blend file because you didn't include the gn node group for both modifiers and it is much easier for us understanding and trying out things. thank you! you can upload blend file by opening blend-exchange.com and following instructions $\endgroup$
    – Chris
    Aug 2, 2022 at 8:56
  • $\begingroup$ Thanks and right ! ok i just uploaded the .blend $\endgroup$
    – Kenji
    Aug 2, 2022 at 9:08
  • $\begingroup$ i am not sure what you want to achieve now? more antennas on the roof? just change distribute to this: [1]: i.sstatic.net/bGUGb.png result: [1]: i.sstatic.net/MmRaJ.jpg $\endgroup$
    – Chris
    Aug 2, 2022 at 9:55
  • $\begingroup$ Actually i want to scatter antennas on the roof , of each building... but for every building their numbers and distribution should be different. Also now, the antennas are scaled with the building since i changed their scales. Basically, 1) first scattering : the buildings 2) second scattering : the antennas but only on the roof (defined by vertex group "roof" on the building01 object. Do you see what i'm trying to achieve here ? Sorry if i wasn't clear earlier $\endgroup$
    – Kenji
    Aug 2, 2022 at 10:07

1 Answer 1

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Instances are objects that's share the same object data. In other words, you can't make different instances, because they just the same. Take a look at Alt + D copies. They are linked, they are instances of the same data, and if you change one of them - the second will be changed also.

Instead of making the building and when distribute it on the surface, do the opposite thing: distribute buildings, realize them and put antennas on the top:

enter image description here

enter image description here

Realize instances doesn't help because i can't access the vertex group on building01 anyway

No, you can. In 3.2 there is a Named Attribute node, that allows to get access to vertex groups

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  • $\begingroup$ Thank you !!!! That's exactly what i wanted to have... "Named Attribute node" got it !! yesss ! $\endgroup$
    – Kenji
    Aug 2, 2022 at 12:30

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