Catenary - failing but appearing - 'for unknown reasons'

Hello everybody,

I am trying to produce a catenary structure which follows a sloping plane.

However when I plug my inputs into the catenary component, I get two runtime errors as follows.

1. Chain computation failed for unknown reasons.

1. Transformation into Catenary solver coordinates failed.

The strange thing is that despite the component turning red, the catenaries do appear and they are semi usable for certain functions (rebuild curves and interpolate), extract control points and even bake! However I am wanting to loft the curves and this comes up with another error

1. The loft failed, possibly because at least one of the sections is invalid

I also have two further questions :

in the rhino file I have baked the catenaries (I have moved them just to remove confusion) and shown the curve start points (using CrvStart - could someone tell me why the curves do not all start at the same side (i have checked the direction of the surfaces (currently hidden) that are used to intersect a curve to get the start and end points of the catenaries, however all these surfaces are all similarly aligned.

Also - what is the best way to 'finish' my loft, i.e. bring the ends down to form a dome like shape rather than a tunnel like shape.

many thanks

J-P

Attachments:

ula 09.3dm, 272 KB
ula 09 - catenary.gh, 11 KB

Replies to This Discussion

Permalink Reply by Hannes Löschke on May 28, 2014 at 6:41am

If something strange happens, most of the time, you are feeding wrong data. Try to verify your data using the Panel, the DataViewer from the View menu or just hover over the out/input.

The intersection returns two points. You're culling one and connect that to both. That's one line across and one with zero length.

That results in one L=0.0 input with a zero length baseline to the catenary. Failing to construct the chain.

Catenary outputs the unmodified zero-length baseline plus the other line that was okay. Loft will fail with zero length segments.

While baking, Rhino will check and remove zero length line.

I have no idea, why the Catenary component decides to flip certain curves but you can realign them easily enough.

Attachments:

ula09catenary_data_revised.gh, 13 KB

Permalink Reply by J-P on June 2, 2014 at 9:19am

Hi Hannes,

Sorry for the late reply, I've been away for a few days. Thank you for your solution, its a very elegant little number, i didnt realise the flip curve had the guide curve input, having read the help i'm still a little confused as to how the guide curve works, but at least its worth giving a go next time i'm having that issue.

Can i ask you one other question, which is (it was mentioned before) how to 'finish' the loft to close off the ends, to produce a dome like structure rather than a tunnel like structure.

I think the reason i'm struggling to manage it, is that i cannot visualise how to go about itor make a plan.

I had got a v complicated method of trimming the base curve (kidney shape) and then omitting the first and last section curve to be lofted and inserted the two trimmed curve as the first and final entry to be lofted

This did work to some degree, but the surface was a little irregular at one of the transitions, its one way to do it but i'm sure there is a better way.

many thanks again

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