Box2D Forums

Hi,

I have a ragdoll simulation for a physics based character up and running in box 2D. But if I try to run it at low frequencies like 60 Hz ( 240 .. or so doesn't work as well ) joints seem to be very unstable and jitter a lot even when I don't apply any forces on the ragdoll. I have to use really high frequencies close to 5000Hz to get a correct behaviour. I am wondering what I am doing wrong to cause this. My character dimensions are that of an average human body in meters and so is the weight for each body part.

When I try to pull the neck the two small bodies which are connected by revolute Joints get broken and they jitter in various positions. I am not sure if I am supposed to require such high frequency for this kind of simulation to work. I am using the standard position and velocity iterations ( 8 and 3 respectively )



Also as you can see there's a gap between the ground plan and the other bodies. Is that due to skin used as a safety region during collisions for polygons ? I am not sure ....

Thanks !
darkZ

Please read this for tips on building ragdolls: http://code.google.com/p/box2d/download ... gdolls.pdf

Thanks Erin ! I am reading it now and also debugging my code at the same time. Seems like you are suggesting that those neck joints are too small to support that big head. Don't know how I would implement a flexible neck or a flexible spine then. My application isn't just going to produce passive ragdolls, but I would make it do a series of physically "accurate" motions like walking, running, dancing etc.

It is likely that you can get all the neck motion you need with a single joint connecting the head to the upper torso. This is how most ragdolls are created.