ODE Tutorial 9: ERP (Joint Error Reduction Parameter)

This page was mainly translated from http://demura.net/archives/9ode by Babel Fish Translation.


ODE (Open Dynamics Engine) lecture time it is 9th. This time when using ODE you must remember, it explains the parameter ERP (joint error Error Reduction Parameter) concerning.

As for ERP it is the parameter which corrects the error of the joint. When repeatedly simulation it keeps, the center of the joint keeps slipping in computing error and the like. With ERP it takes the value up to 1 from 0 that it corrects that. As for 0 as for 1 with the following step error is corrected in 0 vis-a-vis not correcting error completely. As for recommendation value is about 0.8, but default value is 0.2. In the present sample program being not to have set, ERP is calculated as 0.2. ERP cannot recommend is set to 1 densely. As for the gap of the joint because of the error to which various approximate calculations depend the thing which is made completely 0 being not to be possible, it does.

When ERP is set, API below is used. Furthermore, this works to global and corrects the error of all joints.

  • dWorldSetERP (dWorldID, dReal erp)
    dWorldID is the ID number of the world, and erp is a real number from 0.0 to 1.0. The default value of erp is 0.2.

So, as a practice of dWorldSetERP; Inserting dWorldSetERP(world, 0.0) under dWorldSetGravity of sample4, please try executing. Furthermore, in order dWorldSetERP (world,0.0) to add, to be easy to seeas for sample4a whichchanges point of view. With this example being not to correct the gap of the joint, as in the figure disjointed incident occurs.

To be continued.