How to Create a Closed Mesh

[SaSa]

• I have the following shape made of two hyperbolic paraboloid umbrellas:
  

  

• I am trying to close it by connecting the corners and make it look like this:
  

  

In other words, I am trying to create a box with two faces having hyperbolic paraboloid geometry. I attached the GH file.

Thanks.

Hypars-closed-box.gh (89.7 KB)

[diff-arch]

Hi,

Try this:

Note that it’s probably not advisable to weld the two vertices at the box center. It might render the mesh invalid. I’ve thus implemented a tolerance value that can be adjusted to offset the points slightly.

Also note that applying an additional vertex force, like I do, is totally optional, but let’s you play with the shape.

hypar-box.gh (21.0 KB)

[mikity_kogekoge]

The Loft on the very end in the below image needs to be replaced with MeshLoft (should be found somewhere. I don’t have one right now)

The MeshEdge->E1 gives you the boundary edges. So, you can simply connect the two boundary edges to close the surface.

[SaSa]

A quick follow-up question: when I try to calculate the volume for the generated shape, GH can’t do that because it’s an open mesh. How can I close the mesh and obtain volume results?

Thanks a lot for the answer by the way.

[SaSa]

A quick follow-up question: when I try to calculate the volume for the generated shape, GH can’t do that because it’s an open mesh. How can I close the mesh and obtain volume results?

Thanks for your reply by the way.

[mikity_kogekoge]

Hey, I think that’s because the two points at the center are touching. When doing Mesh Join, those two points are merged. Except for those two points, the obtained mesh should be topologically equal to a cube and it should be closed. I think the easiest way to avoid this is to shrink the height of the umbrella a little bit before merging them. It will change the geometry slightly though.

[SaSa]

I tried, but it did not work

Hypars-closed-box.gh (36.3 KB)

[diff-arch]

Here’s a fixed version.

hypar-box-2.gh (18.9 KB)

I got rid of the Kangaroo simulation, since it doesn’t do much anyway - hyperbolic surfaces seem already to get approximated by the constructed mesh faces (?) -, and it is the main culprit in making the different mesh parts hard to join and weld.

Another issue was that I overlooked somehow that the lateral box faces somehow don’t have the same amount of subdivisions as the top and bottom faces and hyperbolic ones, and thus can’t be joined properly (cf. section above).

[SaSa]

Got it. Thanks a lot !