Friction impulse. Need formula.

Math and Physics Programming

Started by Volgogradetzzz March 24, 2011 08:31 AM

12 comments, last by Volgogradetzzz 13 years ago

wildbunny

550

March 25, 2011 04:13 PM

Ok. I think I got it. Thank you.

Are you working in 3d, or 2d? 3d is slight more complex than 2d, but still doable

Cheers, Paul.

http://www.wildbunny.co.uk/blog
http://twitter.com/paul_m_firth

Volgogradetzzz

1,101

Author

March 25, 2011 06:32 PM

@ wildbunny: 2D.

Simply about complex

Endemoniada

431

March 25, 2011 07:52 PM

Volgo, what formula did you end up using and how is it working out ? I'm thinking about adding friction to my 2D simulator as well.

Thanks.

Volgogradetzzz

1,101

Author

March 26, 2011 07:54 AM

According to Erin Catto presentation GDC2006 and as Bow_vernon said, for 2D friction can be count like this:
1. Get normal impulse - see post #8.
2. Get tangent impulse:

var jTnum:Number = -vab.dot(t);

var jTdenom:Number = bodyA.invMass + bodyB.invMass + rap.cross(t) * rap.cross(t) * bodyA.invInertia + rbp.cross(t) * rbp.cross(t) * bodyB.invInertia;

jT = jTnum / jTdenom;

3. You need to clamp friction impulse:

if(jT < -jN * cof || jT > jN * cof)

{

	jT = jN * cof;

}

4. Get total impulse as:

j = n * jN + t * jT

Simply about complex

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Friction impulse. Need formula.

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