What does CFM and ERP stand for in btConstraintParams enum?

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Wil McV
Posts: 18
Joined: Tue Aug 26, 2014 5:46 am

What does CFM and ERP stand for in btConstraintParams enum?

Post by Wil McV »

Hi all,

I'm new to bullet and i'm some joint related stuff with picking like in the examples. the example contains the following code

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          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 0 );
          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 1 );
          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 2 );
          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 3 );
          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 4 );
          dof6->setParam( BT_CONSTRAINT_STOP_CFM, 0.8f, 5 );

          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 0 );
          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 1 );
          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 2 );
          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 3 );
          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 4 );
          dof6->setParam( BT_CONSTRAINT_STOP_ERP, 0.1f, 5 );
My question is, what does CFM and ERP stand for? I can't find it documented anywhere? What are these parameters?

Thanks in advance
Wil McV
Posts: 18
Joined: Tue Aug 26, 2014 5:46 am

Re: What does CFM and ERP stand for in btConstraintParams en

Post by Wil McV »

So no one knows that they are? they just use them with random values and hope for the best results?
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Erwin Coumans
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Re: What does CFM and ERP stand for in btConstraintParams en

Post by Erwin Coumans »

See the Open Dynamics Manual for CFM and ERP:
http://www.ode.org/ode-latest-userguide.html#sec_3_7_0
Wil McV
Posts: 18
Joined: Tue Aug 26, 2014 5:46 am

Re: What does CFM and ERP stand for in btConstraintParams en

Post by Wil McV »

Beautiful :D

Thanks Erwin
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