Pinching Fabric

Hi Guys,

Trying to reproduce the act of pinching fabric using Kangaroo (file attached and image below for guidance).

source: revolutionthreepointoh.wordpress.com

For the fabric I have defined springs on all the mesh edges and the diagonal of their faces with a restlength equal to their length. For the pinching I have tried the two techniques below so far:

1) Moving pinch points as anchor points towards each other.Result below:

2) Creating springs with rest length of 0 between pinch points.

Result below

In both cases, the mesh stayed flat instead of bending with the pinch which would happen in physical tests. In the first case, the mesh edges also got elongated which would not happen in real life.

Do you have any advice how I could get this to work please?

Many thanks,

Arthur

Attachments:

130217_Springs.gh, 24 KB

Replies to This Discussion

Permalink Reply by Daniel Piker on February 17, 2013 at 5:35pm

Hi Arthur,

If you have some geometry all in one plane, and apply forces in the same plane, then the result will stay in that plane.

In real life, if you compress a sheet in plane, there are always imperfections and asymmetries that cause it to buckle one way or the other, but in the simulation these are missing.

Moving one vertex out of plane by a tiny amount, or adding a small out of plane unary force should solve this.

Permalink Reply by Arthur Mamou-Mani on February 17, 2013 at 6:38pm

Hi Daniel,

Thanks a lot for that, very helpful and interesting!

It does works in 3d with the "imperfection" but I get slightly different results depending on which point I chose to apply a small unary force to (or if i choose more than one points). What do you think would be the most accurate solution?

Also, I get a very different result when I increase the rest length of the mesh edges (image below also has different pinch springs). Strangely, the arch that I am getting is a bit closer to what the fabric that I am using is doing in real life (very thick fabric with resistance).

Here is a result with the "anchor point technique" I guess the problem with this one is that the pinching points stay planar whereas in real life they move in space:

I wonder how I could add some "resistance" to the fabric without adding additional values to rest length. What creates the "sponginess" of a foam like fabric?