question about acceptable meshes (tearable)

[danazoid]

Hi, I was testing out tearable cloth today and got the error "ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection."

I did some testing and this is what I got
1) "thick" mesh (my custom mesh that is 2 vertices thick): error
2) plane mesh (and my custom mesh reduced to 1 vertex in thickness): no error
3) simple cube mesh (in-built unity version, vertices 2 x 2 x 2): no error
4) "thick" plane mesh (essentially a simple cuboid with vertices 4 x 4 x 2): error

It seems to me the error occurs when the cloth is "thick" (ie not just 1 vertex in thickness). I don't know about the cube.
I would like to confirm if Obi Cloth is only designed to handle flat, 1 vertex thick meshes.
I want to be able to cut/tear cloths with a thickness to them, do any of your solutions allow that? (eg softbody)
Thanks in advance.

[josemendez]

Hi, I was testing out tearable cloth today and got the error "ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection."

I did some testing and this is what I got
1) "thick" mesh (my custom mesh that is 2 vertices thick): error
2) plane mesh (and my custom mesh reduced to 1 vertex in thickness): no error
3) simple cube mesh (in-built unity version, vertices 2 x 2 x 2): no error
4) "thick" plane mesh (essentially a simple cuboid with vertices 4 x 4 x 2): error

It seems to me the error occurs when the cloth is "thick" (ie not just 1 vertex in thickness). I don't know about the cube.
I would like to confirm if Obi Cloth is only designed to handle flat, 1 vertex thick meshes.
I want to be able to cut/tear cloths with a thickness to them, do any of your solutions allow that? (eg softbody)
Thanks in advance.

Hi Danazoid,

The limitation for cloth meshes is that they cannot be non-manifold: http://obi.virtualmethodstudio.com/manua...tmlanifold, as stated in the manual:

If you're not sure what "non-manifold"means, see:
https://sinestesia.co/blog/tutorials/non...-fix-them/
https://www.sculpteo.com/en/3d-learning-...-geometry/

I would like to confirm if Obi Cloth is only designed to handle flat, 1 vertex thick meshes.

Not sure what you mean exactly by "1-vertex" thick, but non-manifold meshes can be "glued" to a 2-manifold mesh using proxies:http://obi.virtualmethodstudio.com/manual/6.3/clothproxies.html

This does not work for tearable cloth, though. By definition, tearable cloth must be 2-manifold (which is believe is what you mean by 1-vertex thick).

I want to be able to cut/tear cloths with a thickness to them, do any of your solutions allow that? (eg softbody)

Nope, this is extremely costly to do. The reason is that when you cut a surface, you need to update both its physical representation (in Obi, particles + constraints) as well as its visual representation (triangle mesh). For a volumetric shape to be cut, it must be made of tetrahedrons, which are the volumetric equivalent of triangles.

Your best bet to do what you need is find a tetrahedral FEM (finite-element method) engine. To the best of my knowledge, no existing games do this, and there are no implementations of this in the Asset Store.

kind regards,

[danazoid]

This does not work for tearable cloth, though. By definition, tearable cloth must be 2-manifold (which is believe is what you mean by 1-vertex thick).

Thanks for the fast reply!
Can I just check: do you mean that I cannot use the cloth proxy with a tearable cloth?

[josemendez]

Can I just check: do you mean that I cannot use the cloth proxy with a tearable cloth?

Yes, that's what I meant: proxies work by skinning an arbitrary mesh to a simulated cloth. Skinning cannot work if the cloth modifies its topology (ie, tears).