I've got this scene where I'm trying to get a crowd sim working over a terrain. However the cylinders I'm using as people randomly disappear and I'm not quite sure how to solve the issue. Has anyone had any experience doing this kind of thing with geometry nodes? I don't mind what the solution is it doesn't have to be at all what I'm doing but any help would be appreciated thanks.

Blend file:


  • $\begingroup$ Hi Mitchell, i downloaded your file. But i cannot see any cylinder disappearing!? Did you change something in your blender file? $\endgroup$
    – Chris
    Commented Jul 29, 2021 at 12:25
  • $\begingroup$ Sorry, I meant to say when I move the plane around cylinders disappear $\endgroup$
    – Mitchell
    Commented Jul 29, 2021 at 18:43
  • $\begingroup$ Hello and welcome. While files, images, and external videos or links may be helpful additions they should not be the only way to obtain information about your issue. Don't make understanding your question rely on downloading a file, watching a video or visiting an external site. Use the builtin tools to upload images or gifs, along with thoroughly explaining the problem in written form so it can be indexed and searched for thus helping future visitors with similar issues. $\endgroup$ Commented Jul 29, 2021 at 22:13
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    – quellenform
    Commented Nov 3, 2022 at 9:19

1 Answer 1


Possibly a bit too late for you, but maybe it helps anyway:

The problem is that you first adjusted your grid to the terrain with a Shrinkwrap modifier, and made your point distribution on this deformed grid.

Since the Shrinkwrap modifier obviously changes the mesh in such a way that your point distribution also changes spontaneously in some places, your cylinders temporarily disappeared in some places.

Solution (Blender 3+):

If you do without the Shrinkwrap modifier, and first apply the node Distribute Points on Faces on your unchanged grid in the geometry nodes, the distribution always remains the same.

In the Geometry Nodes you can then use Raycast to find out the position of your randomly distributed points on the terrain and instantiate them there.

enter image description here


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