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I'm trying to animate the opening of a book (especially the pages), and the pages turning. For some reason, I can't add a simulation zone without messing up my current node tree. As if it was cancelling some nodes before it (like Set Position). That's my current problem, but my setup being a bit complex, I have to explain it as below.

The blend file :

First here is the book, before and after opening : Main setup at start of animation

Main setup at end of animation

My geometry nodes are a bit on the heavy side, here are the nodes followed by informations :

Geometry nodes setup


To explain all that, here is an annoted version of my setup with the main steps :

  1. Generate a vertical array of horizontal curves (i.e. the profile of each page)
  2. Move left-most handles to follow the book opening (using a rotating empty)
  3. Trim the curves to keep a given length (here 21cm) Then I want to add on top of that, the animation of pages turning. That would the step 4 which I want to place between 2 and 3 (blue arrow). I'm pretty sure I need to use a simulation zone (indepent animation of each page, animation that must changed along time).

Annoted geometry nodes setup

And then, with only the addition of a simulation zone, the step 2 is completely ignored. But not the step 1.

Adding a simulation zone mess up some other nodes

I've got to say, I have no idea why. I'm used to Blender but I think I'm missing something.

  1. Why is the simulation zone cancelling some nodes but not all ? Am I missing some obvious thing ?
  2. Is my way of doing things wrong ?
  3. Should I put everything inside a Simulation Zone ?

Thanks a lot for reading me :)

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  • $\begingroup$ Could you provide your Blender file using blend-exchange.com ? $\endgroup$ Feb 28 at 16:03
  • $\begingroup$ I edited my post with the blend file. $\endgroup$
    – Lutzi
    Feb 28 at 16:07
  • $\begingroup$ As I understand it, every nodes that are upstream the Simulation Input node and linked to its Geometry socket are executed once (at iteration 0 ?). Then the geometry is recycled inside the Simulation Zone. Every nodes that are downstream the Simulation Output node are executed after each iteration. So to get the curves deformed by the Empty, you have to bypass the Geometry socket of the Simulation Input node. Instead, plug it directly "inside" the Simulation Zone. To start with, plug it directly to the "inside" Geometry socket of the Output and you recover the animation. $\endgroup$ Feb 28 at 16:49
  • $\begingroup$ Merci bien ! I get your point, I will try that. Thanks :) $\endgroup$
    – Lutzi
    Feb 28 at 16:52

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