Using simulation islands in bullet

[gunner10]

I'm still coming up to speed with everything this library offers, but I had some questions about its implementation of simulation islands that would be helpful to me.

Let's say I have an elevator kinematic object, and I want dynamic objects to be placed on the elevator and have their movements be done relative to the elevator - e.g. they can move around on the elevator, but the elevators movement is also calculated into the overall movement of the dynamic objects.

This sounds to me like some type of constraint that might exist between the elevator and the dynamic objects. Do I use simulation islands directly to make this happen, the dynamic objects and elevator are in the same island and therefore the desire effect happens?

Or do I create a constriant between the elevator and dynamic objects, and this puts them into the same island?

Or perhaps something else. Any insight would be welcome.

[Erwin Coumans]

What are the main reasons you want to do the calculations in the local elevator space? Can't you just simulate using an kinematic elevator as it is?

Simulation Islands are currently just used for body deactivation, and to group solving of constraints. While it is technically possible to simulate each island in its own coordinate system (and adjust transforms and velocities of all involved bodies relative to the transform/velocity of this coordinate frame), this will complicate things considerably.

If you want to try out this concept, we can discuss things further,
Thanks,
Erwin

I'm still coming up to speed with everything this library offers, but I had some questions about its implementation of simulation islands that would be helpful to me.

Let's say I have an elevator kinematic object, and I want dynamic objects to be placed on the elevator and have their movements be done relative to the elevator - e.g. they can move around on the elevator, but the elevators movement is also calculated into the overall movement of the dynamic objects.

This sounds to me like some type of constraint that might exist between the elevator and the dynamic objects. Do I use simulation islands directly to make this happen, the dynamic objects and elevator are in the same island and therefore the desire effect happens?

Or do I create a constriant between the elevator and dynamic objects, and this puts them into the same island?

Or perhaps something else. Any insight would be welcome.

[gunner10]

Sounds like simulation islands are not a mechanism to achieve what I want.

I have a kinematic elevator as you suggest, but unless its movement is very slow, the dynamic objects start to bounce on the elevator as it moves, which is not the effect I want.

I'd like the dynamic object to "ride" on the elevator, adding the movement of the elevator to any of its movement so that it has the effect of staying on the elevator, regardless of the speed of the elevator.

I'm looking at the available constraints in more detailed to see if thats what I need to use. Any suggestions?

[pico]

Hi,

has anyone found a method to do such "elevator" rides without having the top body fall from the elevator? I think any jump-n-run type of game would need that. How could this be done with bullet?

thanks

[ola]

Hi Gunner,

just a quick input: for your kinematic elevator, are you setting it's velocity as well as the position when you update/move it? If the velocity is set to zero it might cause the jumping, I had something similar a while back.

Best regards,
Ola