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I'm trying to get something that looks like a cloth object pinned to the wall at the corners and centre using cloth sim. I'm having a few issues (not getting enough wrinkles and creases, etc), but currently the biggest problem I have is that the top edge of the object remains almost perfectly straight, whereas a real cloth object pinned to a real wall would sag a bit. I think getting the correct sagging behaviour would improve the other issues I'm having with lack of creases.

Real life example

I'm starting with a plane object pinned in 3 places, with a simple cube behind it to serve as a wall to collide against.

enter image description here

My cloth sim is configured as such:

enter image description here

When I run it, the results aren't too bad, but as you can see the top edge of the banner is more or less perfectly straight, as if the fabric is being stretched between the pins, where in real life the cloth would sag a little between the pins if it wasn't being pulled taut.

enter image description here

I think if I could get the actual pin position to be slightly closer together than the vertex group pins then that may help produce better results. I've tried messing with weights and having different starting angles for the flag when I run the sim, but the top edge always remains straight.

What can I do to improve the results from my sim?

EDIT: I've tried using the "rubber" preset instead of the "cotton" one, and whilst that does product sags, it also doesn't produce much in the way of wrinkles in the material.

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2 Answers 2

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Default settings, just changed stiffness has indicated below:

enter image description here

enter image description here

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  • $\begingroup$ That seems to work to an extent, but it's not entirely problem-free as it reduces the amount of creasing I get (I want it to look fairly creased), and the bottom edge doesn't seem to exhibit much sag. I'll leave it a while and accept this answer unless something that produces better results comes along. $\endgroup$
    – GordonM
    Nov 30, 2020 at 8:34
  • $\begingroup$ Cloth sim won't really crease (I mean like clothes before iron). Consider sculpt tool to do it: use draw brush with a small strength for instance. And try to lower bending in stiffness to around 0.5 for the other aspects. Tell me if that's what you want. But will depend on the resolution of the inner grid $\endgroup$
    – lemon
    Nov 30, 2020 at 8:44
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    $\begingroup$ By sheer chance Youtube threw up youtube.com/watch?v=h3PIlhh9ruw as a suggestion. He's making curtains in this instead of a wall hung tapestry but there looks like there might be some really useful stuff in there. I haven't tried it yet but I'm thinking using a shape key to slightly narrow the image at the top might be a big help. $\endgroup$
    – GordonM
    Nov 30, 2020 at 19:09
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I think I finally cracked it.

Using the answer provided by lemon along with a couple of additional sources, I worked out that using hooks was the way to go.

My first attempt used the shape key feature as mentioned in the Blender Guru video, which worked pretty well, but had the annoying issue that when I wanted to freeze the results in place by applying the cloth modifier, I'd get an error message saying you can't apply modifiers to meshes with shape keys. I could work around that by deleting the shape keys but this was an extra step that I would rather not deal with.

The second attempt used the technique of hooking vertices to empty objects and manipulating them to control the behaviour of the simulation. This produced results similar to the shape key technique, and I was able to apply the modifier when done without having to delete any shape keys, so this looks like the way I'll be going from now on.

Here's what the final result looks like

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