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i'm trying to extrude cells top faces using geo nodes to mimic basaltic rocks design.

When i do it on a basic grid it works no problem but when i try to use quick cells addon to generate cells and then add same nodes it seems thats also sides faces are extruded, how can i fix that ?enter image description here

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  • $\begingroup$ Looks like the addon has added extra geometry. Try using a merge by distance node before the extrude and play around with the value. $\endgroup$
    – James Siewert
    Commented Jan 8 at 1:30
  • $\begingroup$ i was thinking the same at first but i think its not extra geo , extrude node is just taking data from sides faces instead of only top faces, and it then scales them up along the Z axis. $\endgroup$
    – ant0
    Commented Jan 8 at 2:40
  • $\begingroup$ Can you upload the file to blend exchange? $\endgroup$
    – James Siewert
    Commented Jan 8 at 2:42
  • $\begingroup$ yes sure ! here is the link <img src="https://blend-exchange.com/embedImage.png?bid=EevA6BkK" /> $\endgroup$
    – ant0
    Commented Jan 8 at 3:11

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It seems like that add on just creates a bunch of extra geometry by default - the top faces are subdivided strangely so even creating an vertex group of only the top faces and using that to select the extrusion still doesn't fix it.

I just ended up scaling the z to 0 and doing a limited dissolve to get a single face per island. Then the geonodes set up behaves as expected. As long as you don't specifically need that extra geo it should be fine right?

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  • $\begingroup$ Thank you for solving it ! i just watched your file but i do not see the disolve by distance node in geo nodes. Can you show me how you proceeded so i can understand and reproduce it myself. thank you ! $\endgroup$
    – ant0
    Commented Jan 8 at 14:09
  • $\begingroup$ oh i think i get it, you just went to edit mode, mesh, dete, and dissolve faces and vertices right ? $\endgroup$
    – ant0
    Commented Jan 8 at 14:19
  • $\begingroup$ Yes - you can do this with geometry nodes but it's harder. The easy thing is to scale the z to 0 and merge by distance - you can do that with a transform node and a merge by distance node. But there are still tris that create edges. You then you need to dissolve coplanar edges. There are a few threads of how to do that with geometry nodes - but the gist its a process of splitting edges only where the edge angle is greater than zero - converting all border edges to curves, filling the curves, putting things back together and merging by distance again - a lot of work for a simple problem. $\endgroup$
    – James Siewert
    Commented Jan 8 at 16:53
  • $\begingroup$ thank you for the explanation , i did it manually as it is easier and works perfectly. Still interesting tho to understand each ways of doing it. Thank you for your help again $\endgroup$
    – ant0
    Commented Jan 11 at 14:46

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