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Robertochico

No collision between Cloth and Solid

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Hi,

I've been looking for answers for days about that issue but I can't find anything anywhere on that matter. I don't have any collision happening between a cloth object and a solid object but they are both on the same finite element solver, so why doesn't it work ? 
I asked a friend of mine to try and it's the same, he can't have collisions between a solid and a cloth object. Does something changed in v15 ? I've watched tutorials on cloth but they were on v13 so the solver was a bit different and I didn't find any tutorial on cloth for v15.
On a forum a member shared a file that was supposed to work but it didn't, the piece of cloth went straight through the solid, no collision.

Does somebody have information about that issue or do I have to add some node to enable the collision ?

Thank you,
Rob

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share the scene

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Hi Fencer,

To demonstrate the problem I've created a new scene with just a grid, a sphere and a groundplane. The sphere is a solid and the grid is a cloth object. I verified the thickness and everything seems good, but as you can see on the screenshot the cloth object doesn't collide with the sphere.

yf5oCEd.png

 

Rob

ClothSolid_noCollision.hipnc

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The sphere was a bad example because in my real scene it's not a sphere but a structure. And that structure is a solid because it's deformed by another solid and breaks.

I need the collider to be deformed and even fractured and the solid approach worked very well in that case for my simulation, except the cloth doesn't collide with the solid.
What I truly don't understand is why the cloth won't collide with the solid object. It's in the same solver ! It should definitely work, no ?

If my structure was only deforming I could use it as a cloth object with a high stiffness, I've already tried it and it works fine but then I can't fracture it like a solid with tethrahedrons.

qDH51lO.png
 

Cubo_01a.hipnc

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Yeah, it looks like a bug to me too. Maybe nobody use cloth with FEM, because that bug was already in H15 and has not been fixed in H15.5.

I realized the .obj object was missing in the file so I replaced it with a box if you want to try it.

 

wy5TUOz.png

Cubo_01b.hipnc

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If it's not so important you can separate "Cubo" sim with "Cloth".
In first sim save "Cubo" geo to file and then in second use it like ordinary static object.

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I tried it last week but the volume based collision detection is slow and inaccurate even with a lot of substeps, collision passes... I even tried to convert it to a vdb object but it's still very slow. I assumed it would be much faster if the cloth and the solid would collide in the finite element solver directly.

 

Edit : Ok, so I abandonned "volume based collision" because it's bad and slow, the "surface collision" works muck better and is way faster.

Edited by Robertochico

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