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I have a little floating robot character, it's just a sphere with an eye and 4 little "nub" sort of feet legs that extend from it's bottom. I want to do keyframe animation on the sphere, and have the little legs swing and bounce around (within limits on their movement), while attached to the sphere.

I have some limit rotation constraints set up on them but I decided I want to just simulate them like a puppet's feet or something, instead of manually animating them. How can I achieve this? The sphere is not yet rigged and neither are the legs, will I need to rig them to do this? Or can I handle the little feet with physics and constraints alone?

I've tried rigid and soft body and setting their parent empty as a constraint target but the feet just fall down infinitely when I bake the simulation. I've never tried to do simulations so I'm not sure where I should be looking to do this. Also at the base of my little feet I have a small colored ring from which they extend, this is animated using a lattice so that when the feet move, this little "rubbery" part deforms a bit as well, and if possible I'd like to preserve that in any simulation, though it's not that important and I could do without it. I should note that I've done a simple character similar to this before but that was without needing any physics.

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I think what you are looking for is called "ragdoll rigging" which uses Rigid Body Dynamics. Blender Cookie recently had a tutorial and you can find several on youtube

Start with the body. You want the body to be a Passive object that is animated, this will allow you to animate the position of the body and have the legs follow.

enter image description here

Then add a leg which will be an active object.

enter image description here

Next you add an empty to be the pivot point. Locate the empty at the top of the leg at the point where you want it to rotate. Make the empty a rigid body constraint, set type to generic with one object being the body and the other being the leg, turn off disable collisions and turn on the x,y,z axis limits and set all to zero.

enter image description here

You will want to setup the parenting to help keep them together. Select the leg then Shift select the empty and press CtrlP, select the empty and shift select the body and press CtrlP.

Adjust the other rigid body properties so that they behave the way you want them to.

Repeat this for each leg.

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  • $\begingroup$ Ahh this sounds like what I'm looking for, I'll give it a try thanks! $\endgroup$ – Kassandra Mar 17 '14 at 4:08
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I think you mean you want the children objects (i.e. the legs) to follow the parent in a delayed way like this:

enter image description here

To do so:

  1. Parent the feet to the body.
  2. Under Relations Extras in the Object Settings, check the Slow Parent checkbox and set the Offset to 10.0

    enter image description here

  3. This next step is optional, but if you want to prevent the feet from ever getting farther than a few units away from the body, you can add a Limit Distance constraint. Go to the constraints tab, add a Limit Distance constraint, set the distance to something around 4.0 units and set the target to the parent object:

    enter image description here

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  • $\begingroup$ Thats very close to what I want but not quite, the feet are attached to the sphere so I don't want them to move around from their locations, I just want them to rotate as if on a loose ball joint from their current locations $\endgroup$ – Kassandra Mar 9 '14 at 22:26

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