# Physics Simulation Forum

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 Post subject: Friction soundPosted: Wed Feb 01, 2012 7:51 am

Joined: Wed Jan 25, 2012 6:32 pm
Posts: 16
I've managed to do simple contact sound effects (iterating over contact points every simulation tick and taking m_appliedImulse). But how can I implement friction sound (e.g. when vehicle tires slide or a crate being dragged)?

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 Post subject: Re: Friction soundPosted: Wed Feb 01, 2012 3:06 pm

Joined: Sun Jan 01, 2012 7:37 pm
Posts: 55
I think the source engine detects a dragging motion, and then periodically checks if its still dragging or not, so its not a continuous detection, but only once every 200ms or so.

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 Post subject: Re: Friction soundPosted: Thu Feb 02, 2012 3:13 am

Joined: Mon Jul 19, 2010 3:11 am
Posts: 49
I have implemented basic physical sounds effects (impact, scratching), You can find mini tutorial here http://szamq.wordpress.com/2011/09/18/physical-sound/ The frictional sound method is done in the same way like yours - iterating over contacts, but with different condition

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 Post subject: Re: Friction soundPosted: Sat Feb 04, 2012 6:45 pm

Joined: Wed Jan 25, 2012 6:32 pm
Posts: 16
Thank you, it gave me a direction to think on.

And how do you handle rolling objects? They may have opposite velocities, but every contact point will be fixed in objects' local space (if there is no slipping).

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 Post subject: Re: Friction soundPosted: Sun Feb 05, 2012 1:38 am

Joined: Mon Jul 19, 2010 3:11 am
Posts: 49
i haven't implement rolling sound jet, but i believe it can be done like other two sounds by adding another condition which compares angular velocity of two objects body->getAngularVelocity(). Like this:

Code:
if(enough impulse and penetration) impact_sound();
else if(contact point distance < small value && linear velocities difference > small value 2)
{
if(angular velocities difference < some value) rollingSound();
else slidingSound();
}

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