Help How to get collision impulse properly

[josemendez]

I read collision normal impulse, it's said that unit is newtons x time x time, however I am unable to get timestep independent force.
I tried to divide that force by substep time squared or timestep squared, but the value I get is not similar - I would expect to get very similar force whatever the substep count is 4 or 8.

Hi!

Forces are refined over multiple iterations per substep, but they're calculated from scratch for each substep. Callbacks are called at the end of the step after all substeps have taken place, so they only contain data for the most recent substep. This applies to contact impulses as well as all constraint lambda multipliers in Obi.

As a result you won't get the same results with 4 and 8 substeps. This is something I'm actively working to improve in Obi 7.2, by returning the max/average over all substeps.

Also is tangent impulse never set? Or it's set only for particles or mesh colliders (I use SDF)?

Should be set if you're using a collision material with friction greater than zero. Otherwise it's not set, since there's no force being applied in the tangent direction.