Instability in run-time joint creation

Gaming and Visualization Technologies APIs Physics Modeling (closed)
1

Hi,

I have recently started working with nvidia physX (SDK PhysX 2.8.3) and am facing difficulties
in getting into the physX mind.

In particular, I am facing problems with stability when joints are created at
run time. For example,when an object is jointed with a single object the
system is stable and clear. However, when a second element is jointed the
system gets highly unstable including,vibration weird jumps and unexpected
movements.

I was wondering what causes such behaviors and what can be done to stabilize
the system. Also, is there any documentation or books you could suggest to
have a better learning process.

All the best and many thanks for a prompt reply

Yaki Setty

2

Hi,
have you tried looking at the documentation? I’m using 3.2.1 and there are examples there, on how to create joints.
Another thing is what is the distance between joined objects? There are several aspects for joining.
And another thing is what kind of joint you are using ?

3

Thanks for your reply, Jaworekplay.

I have looked deeply into the documentation of 2.8.3 and most of the joints I created are based on their examples. They are very basic though.

I am using 6dof joints and control most of the drives using drive position and springs.

The linked object is very small, therefor the joints are very close to each other. could you please explain more about the aspects of the distance between the joints? and how is best to manipulate this?

Thanks much for the help,

Yaki

4

I use PhysX 3.2.1 and haven’t yet used this type of joints. Are the actors that you join a different types like: rigid or static? I’ll have a go at this 6dof joint and get back to you. Meanwhile just keep on trying altering the settings of the joint i.e. breakable force amount and range. Hope that helps.

5

Have you disabled collision between bodies of joints?

6

Thanks jaworekplay , looking forwards to your insights on the matter. I am trying different values for the forces but none is fully stable. I have managed however to reduce the effect by tuning the drives.

MrOleksandr, yes I have disabled the collisions, however, I would have been great if I could sort a way to leave the collision on, in a way the the objects affects each other.

Thanks again guys

Yaki

7

It’s better if you could post a PVD capture (PhysX Visual Debugger) here so we can visualize what’s going on.

The joints work best when the actors’ masses are in the 1 to 10 range. A 1 kg actor will not behave nicely when jointed with a 1000 kg actor, for example.