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I'm relatively new to geometry nodes and have followed several procedural plant tutorials to get me started. I decided to try and make a procedural fir tree and can't figure out why my secondary branches aren't behaving how I would like them to. I've tried searching on youtube and here for any answers but can't find anything.

Basic Setup: Trunk being the trunk, Primary branches being the branches on the trunk, secondary branches being the branches on the primary branches. I've started off with a Bezier curve for the trunk and then made quadratic Bezier curves in the geometry node tree for the branches. Primary Branches

As you can see in the above picture, the primary branches scale to 0 at the end of the curve which is good. However when I attempt to do the same thing for the secondary branches and plug it in, it doesn't scale down at all. It keeps the same scale for the length of the primary branch. Secondary Branches The red X next to the map range node is the node I'm using to scale just like I did for the Primary branches. I think it has something to do with the spline parameter not doing something correctly for the map range node????? Changing any of the values on the primary branch map range node changes the secondary branch scale equally. Which is why I think the spline parameter factor is not doing what I want it to do. What Spline does the spline parameter node use if there is multiple? Does it only do it for the main object your doing a geometry node modifier for? Or does it go forward through the nodes to the spline connected via nodes?

I've tried all variations with the map range node, and the input spline parameter node(changing from factor to length to index) but it doesn't change anything. Adding a different map range node (with spline parameter factor/length/index) doesn't change anything either.

A solution to fix my secondary branches not scaling down over the curve length would be greatly appreciated, also since I'm new any other pointers would be appreciated.

side note: I've changed radius of branches/trunk to be more visible in the pics, don't think this affects anything.

Edit: here is blend file i've done some other tests on here

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  • $\begingroup$ can u pls upload your blend file? $\endgroup$
    – LuckyOne
    Apr 13, 2022 at 4:07
  • $\begingroup$ almost forgot, here you go $\endgroup$
    – Bean
    Apr 13, 2022 at 4:13

1 Answer 1

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you have to use the capture attribute to get the "right" spline factor:

enter image description here

result:

enter image description here

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  • $\begingroup$ Thank you so much, is there a reason I need to capture the attribute of the primary branches curve instead of copying the primary branches? Why is it different? $\endgroup$
    – Bean
    Apr 13, 2022 at 11:46
  • $\begingroup$ Blender has "somehow" to know which spline parameter you mean, as you know, you can have hundreds of spline in your tree. It does this by checking where you plugged the parameter in and follows those noodles. If this is the wrong (or you want to use another one) geometry, you have to "transfer/capture" the value from one geometry to "another"/modified geometry. $\endgroup$
    – LuckyOne
    Apr 13, 2022 at 12:09

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