What's the use of tool, 'Sort Elements'?

Question

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.

Leander · Accepted Answer · 2019-08-02T08:28:22.763

3

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.

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.

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]

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.

Here is a gif to reproduce the example.

edited Aug 02 '19 at 08:28

answered Aug 02 '19 at 08:00

Leander

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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? – 나미손 Aug 02 '19 at 08:12
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? – Leander Aug 02 '19 at 08:14
Yes it is. I made two objects as you said, but edges of my objects did not zigzag as yours. – 나미손 Aug 02 '19 at 08:22
I showed the steps in a gif. – Leander Aug 02 '19 at 08:28
You are so kind! Thank you very much. – 나미손 Aug 02 '19 at 08:30
One more question. I want notify you with @Leander, but it seems not to operate correctly. I just typed '@' and 'Leander'. What's the problem? – 나미손 Aug 02 '19 at 08:35
I got notified, so I guess it works. If you don't include an @name ping, then the previous comment's owner gets notified anyway. In this case it wouldn't have made a different. For more info, see this answer. – Leander Aug 02 '19 at 08:47
Thank you. Have a nice day! – 나미손 Aug 02 '19 at 09:11
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It is very useful for the Build Modifier. Set the build to spread from a certain point. – rob Aug 02 '19 at 09:33
@rob That's a great example. Would you like to add a separate answer or should I extend mine? – Leander Aug 02 '19 at 09:40
Please extend yours :) – rob Aug 02 '19 at 09:43
@rob your comment is also very good! – 나미손 Aug 02 '19 at 13:31
@Leander So the Mesh > Sort Elements ... > View X Axis are being sorted ascend over view x? – June Wang Oct 23 '19 at 08:40
Yes the vertices will be sorted in X order of the current viewport display. – Leander Oct 23 '19 at 08:46
@Leander Another question, do you know which sorting algorithm is this using? – June Wang Oct 28 '19 at 15:23
Sorry, no I don't, is it too slow for you? – Leander Oct 28 '19 at 19:23

What's the use of tool, 'Sort Elements'?

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