# Community challenge: Create a sort of rope

### » Sun Jan 11, 2009 9:31 pm

all 3 examples so far have problems when the endpoint is an exact location.

what i had in mind was something like this, but also with the ability to move the endpoints around (as if they were fixed to a moving object).

i assume it is because we're all building a directional rope. it seems like we'll need to do some semi-complex math for the joints to treat both endpoints equally.
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### » Sun Jan 11, 2009 11:08 pm

A quick note: If you just want a curve which is in the shape of dfyb's rope picture, you'll get it using hyperbolic functions (which are somehow similar or analogious to trigonometric functions.) Don't ask me how, cause I heard this from my math teacher in hi school, and he didn't tell me anything more about hyperbolic functions. If some math guru knows more about using them, I'll be interested to hear and learn :D

edit: [quote="Wikipedia":3ecd0dd6]Just as the points (cos t, sin t) form a circle with a unit radius, the points (cosh t, sinh t) form the right half of the equilateral hyperbola. Hyperbolic functions are also useful because they occur in the solutions of some important linear differential equations, notably that defining the shape of a hanging cable, the catenary, and Laplace's equation (in Cartesian coordinates), which is important in many areas of physics including electromagnetic theory, heat transfer, fluid dynamics, and special relativity.[/quote:3ecd0dd6]
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### » Mon Jan 12, 2009 12:23 am

[quote="Ashley":1ldvlzrx]Heh, I like the idea of community challenges. Davo and I came up with this one. You'll need the latest 0.98.4.
It doesn't look as good as Squeemish's, but it uses instances of the same object, instead of a load of clones (which would get kinda annoying in the event sheet editor).[/quote:1ldvlzrx]

For some reason I couldnt load yours, it said it was made in a newer version of construct (but mine is up to date, I clicked the update button and it said it was)
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### » Mon Jan 12, 2009 12:25 am

[quote="Chezzy":1yen6r2g][quote="Ashley":1yen6r2g]Heh, I like the idea of community challenges. Davo and I came up with this one. You'll need the latest 0.98.4.
It doesn't look as good as Squeemish's, but it uses instances of the same object, instead of a load of clones (which would get kinda annoying in the event sheet editor).[/quote:1yen6r2g]

For some reason I couldnt load yours, it said it was made in a newer version of construct (but mine is up to date, I clicked the update button and it said it was)[/quote:1yen6r2g]

You need 0.98.4. The update system won't be telling you about the new version until it's been proven that the latest version is stable enough. You can download .98.4 HERE.
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### » Mon Jan 12, 2009 12:26 am

You're using 0.98.3, update to 0.98.4, it's on the forum but isn't sending update notifications yet.
Scirra Founder
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### » Mon Jan 12, 2009 7:36 am

Thanks, great update btw
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### » Wed Jan 14, 2009 5:40 pm

[quote="Drasa":11en0wky]A quick note: If you just want a curve which is in the shape of dfyb's rope picture, you'll get it using hyperbolic functions (which are somehow similar or analogious to trigonometric functions.) Don't ask me how, cause I heard this from my math teacher in hi school, and he didn't tell me anything more about hyperbolic functions. If some math guru knows more about using them, I'll be interested to hear and learn [/quote:11en0wky]

Ooh, math! I can't wait to take a crack at this after my exam today.

Does Drasa's idea meet all the requirements? Because I'm sure that this is the best way go about this rope business. Wikipedia points out that the equation for a catenary is:

But I think we would need a more general form. Maybe

Then you get the two endpoints for the rope, plug them in for x and y to get values for x0 and y0. That leaves a which will basically determine the stiffness of your rope, so you can set it at whatever looks good.
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### » Sat Jan 17, 2009 11:56 am

that's a nice example of using ropes in game
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