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New here, hope this is the proper board for this kind of question.

I'm relatively new to Blender, and I've had cases where I'd like to separate an object that's becoming a bit cumbersome to handle into separate meshes. For instance this, I made a helmet with a rim (or whatever you call the extrusion near the edges) like this:

Extruded rims

Turns out the rims almost needed more vertices than the rest of the helmet, and handling their material etc. would be easier if they were a separate object. I tried keeping the whole thing relatively low poly and achieve the curves etc. by using subdivision surface, like so:

Wireframe before subdivision

My question is, what's the "correct" or most common way to go about this; I could just select the faces near the edge and separate them & fill the missing faces to make them watertight, but then the subdivisions wouldn't make the helmet match the rim's lines etc. exactly anymore and there would be some ugly gaps between the two. I could approximate this by fiddling with edge creases & careful positioning of the vertices that "meet" the other object, but I'm not sure this is the way to go. Is there any way to "match" or attach vertices in an object into ones in another object, so the two would line up perfectly, while still keeping the objects themselves separate?

Or am I just doing it wrong, and keeping it as a single, bigger mesh would be preferred?

This might be a very basic thing, sorry about that - it's just something that's been bugging me and I'd like to learn the correct method instead of having to adjust something I came up with later on. Thanks in advance!

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    $\begingroup$ I don't understand why you need to separate a mesh for the sake of material management. You can have a different material slot for the rim and for the rest of the helmet. Separating objects is useful whenever you want to have separate modifier stacks (and few modifiers support vertex groups), or separate transformation matrices, or separate parents etc. $\endgroup$ Commented Jan 17, 2022 at 22:58
  • $\begingroup$ That's basically why I want them separate - I want to sculpt pretty fine details into the helmet's faces (to be baked into normals later), so I need to subdivide the mesh by a lot to get enough geometry for sculpting without ugly edges etc. I could use dyntopo, but it doesn't support the layer brush. If I have the rims in the same model, subdividing the whole thing by a lot adds way too many vertices / faces & my machine can barely handle it. $\endgroup$
    – Dropboar
    Commented Jan 18, 2022 at 8:47

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Based on my understanding of your problem, you could separate by material slots.

Assign different material slots for the fragments of your mesh you want to separate:

It doesn't matter what materials are assigned to the slots, e.g. a single material can be assigned everywhere and the mesh will still be separated - I use different materials to visualize how I want to split the mesh. The point is to use different Material Slots, not necessarily different materials.

Subdivide:

Add a simple geometry nodes setup:

For the 0 input of the geonodes modifier only the geometry with first (0 index) material slot will be visible:

If you duplicate it, and increase the input to 1, you will get seemingly the old shape, but separated into two objects:

Now you can for example apply the modifiers of one of the parts, subdivide it more, and sculpt it. Just keep in mind to Keep Corners:

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a.Make your selection. Then you can create a vertex group out of your selection. If you miss anything it is easy to edit or reload. enter image description here

b. In edit mode, You can either Press shift+d to duplicate your selection, to leave your model untouched, or skip this step to do a cut and copy

c. Press P and choose selection

enter image description here

You now have a separated part of your mesh. Other more advanced users may have different advice, but to me it is looking fine when you subdivided, so, consider keeping everything the way it is, and saving a selection group so that you can easily change the material of that detail.

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  • $\begingroup$ That's what I ended up doing; just mostly wondering if I could somehow attach the adjoining vertices / edges between the two meshes to each other, since I needed to fine tune some locations so they match better when separated. $\endgroup$
    – Dropboar
    Commented Jan 18, 2022 at 8:48

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