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TLDR: I want the subdivides on this to look like this so that it simulates properly

I'm planning to do a thick cloth simulation using mesh deform in a couple of days, and I've been practicing with simple geometries-- the problem is even these simple geometries seem to import horribly with their subdivisions, and when I go to simulate, the messy subdivisions create a mess.

I've inserted a couple images of the messy subdivides, and a gif showing an error of one simulation I did.

here are the messy subsurface divides from today

here are the messy sub divides from yesterday which are even worse

here is the thick mesh i'm simulating, which works perfectly

gif of the simulation error

But THIS type of subdivisioning is what I need! It's from a tutorial I was watching and I'm assuming he built the object in blender which explains the insanely beautiful clean subdivides.

I've tried cleaning up the subsurface through limited dissolve but that doesnt work because the simulation doesn't work on one face and if I try to add a subsurface modifier it becomes very messy again. I basically just need an even square/ rectangular divide which currently is only possible for me to do if I make the original object on blender, which I won't be able to do soon once I need to use some more complex rhino models.

The subsurface divide modifier is just very confusing to me in general because it closes holes in my models, and generally doesn't seem to do what I want if it's not just a rectangle. I might just be confused on how it works though.

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The subdivision surface modifier is optimized for meshes that are entirely (for the most part) constructed of quads. Your CAD imports have a lot of uneven topology and tris. This is inevitable when you are working in CAD programs with NURBS and then are forced to convert them to polygons so you can open in Blender (or other mesh based modeling tools). It's why you are getting ugly results with the subsurf modifier.

Here is how cloth simulation works "under the hood" (Straight from the blender docs):

Cloth Simulation

As you can see from the above, accurate simulations depend on even topology so it can compute springs properly.

Unfortunately there is no magic button or export option that will fix your problem. Blender can't natively import NURBS - at some point in the pipeline you are converting from parametric data to polygons and horrible topology is inevitable.

The closest thing to an "easy fix" would be to import your model into ZBrush, and use ZRemesher.

Beyond that, your only other option is to remodel/retopologize the cloth you want to simulate using traditional subd modeling techniques.

Hope this helps.

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    $\begingroup$ Thanks. Zremesher worked perfectly. I also think this quad remesher for blender would work as well but I didn't want to pay. exoside.com/quadremesher $\endgroup$
    – omid
    Jun 28 '20 at 18:32
  • $\begingroup$ Glad to hear it and happy to help! Quad Remesher actually looks pretty damn good. I didn't realize that auto-retopology tools have come that far. A bit pricey though. $\endgroup$
    – Jay
    Jun 28 '20 at 18:39
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Beyond that, your only other option is to remodel/retopologize the cloth you want to simulate using traditional subd modeling techniques.

Manually remodeling/re-topologizing is not the only other option. You can get surprisingly good results in Blender with the Quadri-flow Remesh tool. I don't know it to have a UI location yet, but you can use the Search function to find it (F3). Make sure you're in Object Mode before performing the search.

I don't know if the button-like objects in the OP's pic are a separate piece from the main mesh or not. But if they are not separate, the OP might want to edge split, and then separate them, before performing the remesh, so that the buttons are not included in the remesh calculation, so that their existing topology will be preserved. Even doing this, however, it could easily be the case that the new surfaces won't have a consistent number of spans for easy rejoining and merging afterwards. So it might be better to just keep them separate pieces, and vertex parent them to the newly regenerated base mesh. Remeshing the base mesh should be relatively straightforward using this tool.

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  • $\begingroup$ thanks. The quadri-flow seems to not be perfect, but I also found a quadremesher for blender that seems to be perfect. exoside.com/quadremesher $\endgroup$
    – omid
    Jun 28 '20 at 18:34

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