Soap-film elements example

Attached below is the example file shown in this image I posted a while back:

http://www.grasshopper3d.com/photo/soap-film-elements-and-geodesic-...

The soap-film 2d triangular element properly discretizes the area continuum forces, so they are independent of meshing density, unlike simply using a network of 1d springs.

The warp and weft stresses can also be set separately allowing greater control of the shape (making them equal will give minimal surfaces).

Because the soap film elements alone do not have any in-plane stiffness, it can often be useful to have some spacer elements to keep the nodes well distributed.

Also, if mesh edges follow geodesics on the surface, it helps keep the strips straight when unrolled, allowing more efficient use of material.

The G-string component can be used for both - keeping the nodes well spaced, and aligning edges with geodesics. It pulls each node toward a combination of its neighbours, but taking only the part of the force tangential to the surface, so it does not interfere with the shape of the surface, only affecting how the nodes are distributed on it.

The "GeoIndex" input lets you choose which neighbours will be used here. In this example, a quad mesh is used, and index 0 and 2 give the neighbours in the warp direction, while 1 and 3 are in the weft direction. Note that it is the triangulation of this quad mesh that is used for the actual soap-film elements.

There is also a "spacing" option. If this is true, the nodes will try and space out evenly along the geodesic, while if it is false, only the direction is affected. In this example it is set to false for the warp and true for the weft.

The example also includes use of the stripper and unroller components to get the flat strips. I have shown the result of splitting in either direction, and as you can see, only one of these is straight.

Finally, if all of this sounds overly complex, don't worry - for quick studies you can still use the simpler approach of just turning all edges of a mesh into springs, and provided you have a decent starting mesh, the result will be very similar to using the 2d element method given here. This is just provided for those that want to take things to greater degree of accuracy and further towards fabrication.