Simulation (cloth) very slow

[Jason Weise]

I am trying to do a small animation in Blender and have gone through all the usual steps to import with this plugin (which works fantastic) but I am getting held up at the cloth simulation step (this is for clothes on the character)

I am finding that after clicking the relevant simulation buttons in the plugin everything appears setup fine but the actual simulation speed is horrible.

I am getting on average 0.05 frames per second and that is with the cloth set to only collide with the special collider that the plugin creates.

How is everyone else doing cloth simulation with these characters? Surely I have missed an important step. Even if I waited 1 second per frame knowing that there are physics calculations needed, but the speed I am getting is crazy slow.

My PC performance I expect is not the problem as I have the following spec:

Intel i9

64GB Ram

Nvidia 3090RTX

[CookItOff]

I use Blender’s cloth simulation which I assume the add-on does too; it just auto sets things for you.

Having slow simulation calculations is the norm for Blender.

Things to help speed things up:

Have the Subdivision Surface and Collision modifiers AFTER the cloth modifier in the modifier stack on both character and cloth, unless you’re needing the extra geometry simulation resolution. More geometry the slower the sims.

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And second use less geometry unless needed.

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[Alessandro Padovani]

daz studio 4.15, blender 2.93, diffeomorphic 1.6

ryzen 2200, gtx 1060

In general dforce will be faster than the blender cloth, because dforce uses the gpu while blender uses the cpu. For example to simulate the bardot skirt on my system it takes 30 seconds with dforce and 90 seconds with the blender cloth, for 60 frames of simulation.

The default values in blender are there to get a similar precision as dforce. That said you can lower the simulation precision from 16 to 8 and it will work fine enough if you don’t have fast movements in your animation. Or remove the self collision if it is not essential for your simulation.

With precision 8 and self collision off I go from 90 to 30 seconds in blender, thus getting a similar speed as dforce. But this will not deliver the same precision of course.

edit. important. the cloth simulation in blender is not multithreaded. That is, blender can use multiple cores but one core per item. So if your scene gets four cloth items then blender will use four cores for the simulation. But if your scene only gets one cloth item then blender will use one core for the simulation.

https://devtalk.blender.org/t/multithreading-where-is-blender-slow/16921/24

steps:

1. import g8f with the bardot skirt
2. make simulation (advanced setup > simulation > make simulation)
3. bake (cloth > cache > bake)

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[Thomas Larsson]

There is a tool that makes a very low-poly cage for the genesis characters. That cage could perhaps be used as a deflection surface to speed up collision detection, see http://diffeomorphic.blogspot.com/2021/04/simulations-moved.html. Alas, it is a different mesh so the collision detection is not perfect.