PxArticulation::applyImpulse - documentation contradictory

[philipguin]

So looking in PxArticulation at the documentation for methods applyImpulse and computeImpulse, they're described as affecting the "entire" articulation, while also accepting a link parameter described as "the link to which to apply the impulse." What do I expect here? Why does it accept a pointer to link instead of a reference? Can I leave it NULL to affect the entire articulation as desired (e.g. in the case of gravity?) Or can I only affect one link per call?

[kstorey-nvidia]

You must provide a link that the impulse is applied to. The impulse applied to that individual link will be propagated through the entire articulation. This can cause a change in velocity of some or all of the links in the articulation, depending on the degrees of freedom of the articulation and the direction of the impulse.

[philipguin]

I see. So is this is a natural consequence of joints acting as "constraints"? I would normally think of forces as propagating over time via simulation, but I suppose a constraint would mean that the change is propagated instantaneously, by definition. For something like gravity, then, I suppose I would just call "applyImpulse" for each individual link? Sounds like order may be an issue.

[kstorey-nvidia]

If you apply forces on all links, the resulting velocities should be the same regardless of the order in which you apply them