Re: [Algorithms] Formula for Damping f times

[Ola O. <ola...@gm...>]

> x *= 1.0f-(k*deltaTime);
>
> So k = 1 = damped to zero velocity over 1 second at 30fps.

Hm, zero after one second? Really? If we have 30 fps and deltaTime thus is 
1/30 (and k = 1 as stated), then the rhs = 29/30, expanding that would mean 
that x30 = x0 * (29/30)^30 which is approximately x30 = x0 * 0.36

I did get up at 5am this morning so I apologize if I missed/messed something 
here, but that appears a fair way from zero.

cheers
.ola

----- Original Message ----- 
From: <Pau...@sc...>
To: "Game Development Algorithms" <gda...@li...>
Sent: Friday, June 05, 2009 12:31 PM
Subject: Re: [Algorithms] Formula for Damping f times


> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
>> Hi,
>> This is a semi-trivial but I can't quite remember the answer, even
>> though I've done it before.
>>
>> I have an update function sort of like this..
>>
>> void updateX( float deltaTime)
>> {
>>    x = x*k;
>> }
>>
>> k is a constant less than 1.0.
>>
>> Now to do the damping properly I need to perform "x=x*k" deltaTime
>> times, where deltaTime is a fraction.
>>
>> Can anyone help with this please? I recall it just being a log or
>> something.
>
> We just do something very simple:
>
> x *= 1.0f-(k*deltaTime);
>
> So k = 1 = damped to zero velocity over 1 second at 30fps.
>
> Cheers, Paul.
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