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enter image description here

Because I'm not good at English, no matter how hard I read Blender manual, I don't understand the precise meaning of the tool, 'sort elements'.

What's that tool?

There's no tutorial about that tool in Youtube, so I didn't know When I should use it.

Please show me a example in which 'sort elements' must be used.

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For almost all operations, there is no need to resort the geometry.

In a blender mesh, every vertex has index. The indices are usually set in the order, in which the vertices have been created.

I have created the vertices in this figure in this order.

indices

Executing a short python script, we can confirm find out, that the actual indexed order is different. (When executing the following python scripts, toggle at least once into object mode to update the vertices property.)

import bpy

ob = bpy.context.object

# get x coordinates for every vertex
x = [v.co.x for v in ob.data.vertices]

print(x)
# >>> [0.0, 2.0, -1.0, 1.0, -2.0]

This is the indexed order of the vertices.

indexed order

However, when we select the vertices and execute Mesh > Sort Elements ... > View X Axis, the order has changed and the vertices are sorted.

>>> [-2.0, -1.0, 0.0, 1.0, 2.0]

order has changed

All operations (internal or scripted addons), which are dependant on the index, are affected when resorting the indices.

For example, I executed W > Randomize Vertices on two meshes. The right mesh has been sorted prior. The results are different.

randomized vertices

Here is a gif to reproduce the example.

example

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  • $\begingroup$ thank you,@Leander. But this is hard to be understandable to me. In your example, before you executed randomize, how did you make your two objects? $\endgroup$
    – 나미손
    Aug 2, 2019 at 8:12
  • $\begingroup$ I added a plane and subdivided it, then I duplicated it. Now, I have two subdivided planes. On the right plane, I executed the "sort" command. After that I executed the randomize command on each plane. Is this what you asked? $\endgroup$
    – Leander
    Aug 2, 2019 at 8:14
  • $\begingroup$ Yes it is. I made two objects as you said, but edges of my objects did not zigzag as yours. $\endgroup$
    – 나미손
    Aug 2, 2019 at 8:22
  • $\begingroup$ I showed the steps in a gif. $\endgroup$
    – Leander
    Aug 2, 2019 at 8:28
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    $\begingroup$ It is very useful for the Build Modifier. Set the build to spread from a certain point. $\endgroup$
    – rob
    Aug 2, 2019 at 9:33

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