How to apply different timestep depending on object

[thorlak]

Is it possible with Bullet to apply different timestep values to different physic objects?

Basically I would like to know if it's possible to enable some kind of Slow Motion effect so that the whole world moves at a slower speed except for specific objects (such as the player), which have a non modified timestep.

Where should I look at in the Bullet Source, or how could I implement such feature?

[thorlak]

Maybe creating two dynamic worlds and updating each one with a different timestep values? But in that case, would the objects of both dynamic worlds be able to collide between each other?