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From: Stephen
Subject: Bouncing stick.
Date: 27 May 2008 08:42:26
Message: <ub0o34h3cumj76k5tpdu1vqt017dn6s24s@4ax.com>
Can anyone give me a pointer on how to calculate/work out how a stick
would fall then bounce when it hits a sloping floor?
I could do a simple sphere but my brains are wracked with a cylinder
:)
-- 

Regards
     Stephen


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From: Aydan
Subject: Re: Bouncing stick.
Date: 27 May 2008 10:25:01
Message: <web.483c191883d861a21ccf29180@news.povray.org>
Stephen <mcavoysAT@aolDOTcom> wrote:
> Can anyone give me a pointer on how to calculate/work out how a stick
> would fall then bounce when it hits a sloping floor?
> I could do a simple sphere but my brains are wracked with a cylinder
> :)
> --
>
> Regards
>      Stephen

This is non-trivial. You have to keep track of the angular and linear velocities
and be aware of the momentums and forces involved


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From: Stephen
Subject: Re: Bouncing stick.
Date: 27 May 2008 11:20:30
Message: <3l9o3491d2kavbbn33qg70a9puensrirfe@4ax.com>
On Tue, 27 May 2008 10:22:16 EDT, "Aydan" <hes### [at] hendrik-sachsenet>
wrote:

>Stephen <mcavoysAT@aolDOTcom> wrote:
>> Can anyone give me a pointer on how to calculate/work out how a stick
>> would fall then bounce when it hits a sloping floor?
>> I could do a simple sphere but my brains are wracked with a cylinder
>> :)
>> --
>>
>> Regards
>>      Stephen
>
>This is non-trivial. You have to keep track of the angular and linear velocities
>and be aware of the momentums and forces involved
>
Yes Aydan it is non trivial :)
I might look at Mechsim, someone in the Bishop3D group has done some
work with it in MegaPov. Oh! The joy of learning it keeps my mind
supple :) And There is all of 82 days left before the TC-RTC animation
deadline.

Thanks for your reply
-- 

Regards
     Stephen


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From: scott
Subject: Re: Bouncing stick.
Date: 28 May 2008 04:27:12
Message: <483d1760$1@news.povray.org>
> Can anyone give me a pointer on how to calculate/work out how a stick
> would fall then bounce when it hits a sloping floor?
> I could do a simple sphere but my brains are wracked with a cylinder
> :)

Three different methods I can think of (easiest and least realistic first):

1) Assume the stick is two point masses in 3D connected by a (stiff) spring. 
Then, you can just deal with the two point masses by themselves, but add in 
an extra force for the spring connecting them.  If you make the spring stiff 
enough it will look ok, you might need to use quite small time-steps though 
to stop the spring exploding.

2) A kind of half-way stage would be to simulate the stick falling in 2D, 
and assume it's just a line, that might make the maths a bit easier, 
although you'll still need to mess about with moments of inertia and angular 
velocities, just not in full 3D.

3) The more complex and correct way is as Aydan said, you need to also keep 
track of the angular momentum and orientation of the stick (in addition to 
the linear momentum and position) all in 3D.  When either end comes into 
contact with the ground you then need to apply a force and a torque to the 
stick that will keep it above the ground.  You'll need a good knowledge of 
3D kinetics to make this one work - like how torques in 3D affect the 
angular velocity, and how that affects the orientation etc, it's not as 
simple as the linear cases, using quaternions makes things easier.


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From: Thomas de Groot
Subject: Re: Bouncing stick.
Date: 28 May 2008 04:30:05
Message: <483d180d$1@news.povray.org>
"Stephen" <mcavoysAT@aolDOTcom> schreef in bericht 
news:3l9o3491d2kavbbn33qg70a9puensrirfe@4ax.com...
>>
> Yes Aydan it is non trivial :)
> I might look at Mechsim, someone in the Bishop3D group has done some
> work with it in MegaPov. Oh! The joy of learning it keeps my mind
> supple :) And There is all of 82 days left before the TC-RTC animation
> deadline.
>

I have PoserPhysics. I could try this out and see how it goes? Otherwise, I 
suppose Mechsim should be very appropriate. I have no experience with it 
(until now) .

Thomas


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From: Warp
Subject: Re: Bouncing stick.
Date: 28 May 2008 04:31:30
Message: <483d1862@news.povray.org>
scott <sco### [at] scottcom> wrote:
> Three different methods I can think of (easiest and least realistic first):

  The easiest way is to simply use a free physics engine (there are many
available). Someone else has already done the necessary math.

-- 
                                                          - Warp


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From: scott
Subject: Re: Bouncing stick.
Date: 28 May 2008 04:39:36
Message: <483d1a48$1@news.povray.org>
>> Three different methods I can think of (easiest and least realistic 
>> first):
>
>  The easiest way is to simply use a free physics engine (there are many
> available).

I don't think that would be easier than my first suggestion.


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From: Stephen
Subject: Re: Bouncing stick.
Date: 28 May 2008 06:01:30
Message: <q9bq341m12csp7u5c1tj6lb55fuvjqtnrj@4ax.com>
On Wed, 28 May 2008 10:27:11 +0200, "scott" <sco### [at] scottcom> wrote:

>
>Three different methods I can think of (easiest and least realistic first):


Thanks, you and Warp have given me something to think about.
-- 

Regards
     Stephen


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From: Stephen
Subject: Re: Bouncing stick.
Date: 28 May 2008 07:28:50
Message: <cbgq34plqtmqfclugf43th51j3k08r699s@4ax.com>
On Wed, 28 May 2008 10:30:06 +0200, "Thomas de Groot"
<t.d### [at] internlDOTnet> wrote:

>
>I have PoserPhysics. I could try this out and see how it goes? Otherwise, I 
>suppose Mechsim should be very appropriate. I have no experience with it 
>(until now) .

That would be good if you could. If you can get a simple demo to work
I will probably buy <gulp> it :)
-- 

Regards
     Stephen


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From: Thomas de Groot
Subject: Re: Bouncing stick.
Date: 28 May 2008 07:55:00
Message: <483d4814$1@news.povray.org>
"Stephen" <mcavoysAT@aolDOTcom> schreef in bericht 
news:cbgq34plqtmqfclugf43th51j3k08r699s@4ax.com...
>
> That would be good if you could. If you can get a simple demo to work
> I will probably buy <gulp> it :)
> --

Hmm. I am going to try this.How much is the floor sloping?

[My first experiment ended in a crash of Poser...]

Thomas


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