60fps is smooth 
no need to interpolate, if it doesnât look smooth something else is wrong.
taken from advanced user doc on physics
Bullet physics runs internally at 60fps by default. This rate is not dependent on the actual framerate and it does not lock the framerate at 60fps. Instead, when the actual fps is higher than the physics framerate the system will display interpolated positions for the physics objects. When the framerate is lower than the physics framerate the physics space will be stepped multiple times per frame to make up for the missing calculations.
hope that helps
instead, when the actual fps is higher than the physics framerate the system will display interpolated positions for the physics objects
I don't believe that happens with character control objects. Infact, I know it doesn't with them, less sure with ridgid body but I believe these are also only updated when they are 'dirty' w.r.t the physics update.
@normen I couldn't agree more. But if I wanted to run my physics as 20fps it isn't so smooth anymore :)
I am currently running at 30fps and it looks fine at this rate, I just wondered if I was missing something obvious. Nothing to worry about, just curious.
Matt
Yeah, youâre right, the character is not interpolated as its a combination of a ghost object and a kinematic body. Using 20fps physics will make the physics as accurate as it looks then I am afraid, really no point in going below 30 fps.