[1.9.8]Thin rope makes itself explode

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[1.9.8]Thin rope makes itself explode

Postby mori-d » Sat Jul 23, 2011 9:00 am

See below scene.
http://www.algodoo.com/algobox/details.php?id=56409

P.S.
I've reported this issue from bug-reporting function of Algodoo 1.9.8b.
But I couldn't confirm that it had really reached to developers...
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Re: [1.9.8]Thin rope makes itself explode

Postby Kilinich » Sat Jul 23, 2011 9:08 am

I would say - all low density things makes itself explode with new solver :(
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Re: [1.9.8]Thin rope makes itself explode

Postby emilk » Mon Jul 25, 2011 9:32 am

You bug report did indeed come in, and I have answered you by mail (if the new system is working correctly...), but here's my answer so that everyone can see:

Large mass ratios (heavy object interacting with light object) is always a problem in simulations. Algodoo:s new direct solver does an incredible job on this, but it's still not perfect. In particular, stiff ropes still causes instabilities. Right now there isn't much to do about this other than making thicker ropes, heavier ropes, or making the rope softer.

This last options is probably the best one. To change the spring constant of new ropes, set Tools.ChainTool.springConstant to something lower than the default 1e6. For instance, a springConstant of 10000 will make a very stable rope for most situations, but will also make the rope more stretchy. It's a tradeoff.

Maybe the default rope spring constant should be even lower. I lowered it from 1e7 to 1e6 in 1.9.8, but maybe 1e5 or even 1e4 will do? With 1e4 a rope would stretch a meter when holding up 1000 kg.

Tell me what you guys think!
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Re: [1.9.8]Thin rope makes itself explode

Postby Kilinich » Mon Jul 25, 2011 9:50 am

Add rope spring constant into interface and auto-adjust it depending on density (actually was suggested before) :D .
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Re: [1.9.8]Thin rope makes itself explode

Postby motoxlife08 » Fri Nov 04, 2011 3:56 am

if you type in Tools.ChainTool.springConstant = 1e5, 1e4... it fixes the problem when you make a loop out of the rope
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Re: [1.9.8]Thin rope makes itself explode

Postby emilk » Tue Nov 08, 2011 10:31 am

Any chain constant above 10^5 is considered "dangerous". Use with care. If your rope explodes, simply lower its strength.
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Re: [1.9.8]Thin rope makes itself explode

Postby Kitesurfer » Wed Mar 10, 2021 3:24 pm

When I need an ideal rope, that is one that doesn't push and just pull when stretched, and doesn't do anytning else (like bend around a wheel or advanced stuff that real ropes do) I make one in Thyme. It is a spring with a postEvent code that sets the spring constant and damping high when the spring is stretched, and low otherwise. To pull and slacken the rope I change its length in the onKey event.
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Re: [1.9.8]Thin rope makes itself explode

Postby FRA32 » Fri Mar 12, 2021 9:36 pm

Kitesurfer, this thread is almost 10 years old. Replying here wont contribute to any conversation anymore and is considered a massive necropost.
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Re: [1.9.8]Thin rope makes itself explode

Postby Kitesurfer » Tue Mar 16, 2021 12:16 pm

Thank you for the guidance, FRA32.

As a newcomer on the site, I found some of the old posts very useful. Ropes explode, TotImp(3) shows force divided by sim.frequency, objects may be put inside geometries - this and others are insights you don't find in manuals or among the heaps of old help-me-with-this-and-that posts. I thought by pointing out the usefulness in a comment thus giving them a fresh timestamp would make it easier to find the really useful stuff.

But maybe there are better ways? And maybe there is a value in letting what's sleeping be left in peace?
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