Gridshells

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My students and I are trying to figure out how to use the wire solver to simulate the construction of a grid shell roof. These types of roofs are often constructed flat on the floor (as a grid of linear elements) and then pushed up at various points to create a curved roof structure.

http://en.wikipedia.org/wiki/Gridshell [en.wikipedia.org]

In houdini, I am starting with just a single wire - i.e. the 2d case. (Once I have that working, I will extrapolate to 3d.) I want to lay my wire flat on the floor and then push it up a bit at the centre.

What kind of force should I use to push up?

See attached attempt that does not work - using the point force. I am not sure how to stop the point force after a certain height…

Attachments:
gridshell_test1.hipnc (121.2 KB)

Patrick
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I have tried applying a mask to the point force - seems to work… Is this a good way to do it?

See attached file.

Attachments:
gridshell_test2.hipnc (133.0 KB)

Patrick
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Here is the 3d version, also using a point force. It seems to be doing the right kind of thing.

But one issue seems to be that once the grid comes out of the force field, the whole thing actually bounces a little… we dont really want this bounce since in reality it would be raised very slowly.

Is there a way to reduce the upward force when it comes close to the end of the force field.

(I guess we could also add more dampening… but this might have other side affects that we don't want.)

Attachments:
gridshell_test4.hipnc (228.1 KB)

Patrick
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Here's another approach to consider using the Spring sop. It's very simple and using grouping to control what is and is not influenced by the Spring forces.

Attachments:
spring_sop.hipnc (40.5 KB)

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