integrated bullet questions...

hi I have a few quick questions mostly about the bullet physics… but also blender in general.

1, Is there any way use a negative margin for collision, or is that absurd? I want to use rigid body physics with a softbody mesh, meaning I need the equivalent of having a rigid body margin around -0.2 to give the softbody some room to work and yet have it deform well.
2, If I scale an animated rigid body from very small to very big and THEN activate the animation… the friction seems to be effected somehow, it makes the mesh very slippery even if both meshes have a surface response friction of 1. I am aware that scaling rigid bodies is a bit of a nono but its seemingly the best way of doing what I need.
3, on creating rigid body contraints, where exactly is the origin of a generic or generic spring joint, located. should i be using empties for these?
4,if i constrain a long chain of rigid bodies, such as a ragdoll setup or even a simple rope, i see twitching… the whole rigid body rig seems to twitch around when the joints reach their limit, increasing physics settings in the world tab doesn’t really help, I also disabled collision between all constrained bodies. even using split impulse didn’t help :frowning:
5, (non bullet related)
I need a way to use something like and xbox controller to drive keyframable attributes… please help… does anyone know of such an addon, even a different build if-needs-be.

I hope someone may be able to shed some light on these questions, as I’m having a hard time with the scene I’m making, which I would upload, but its nearly 500mb and is commercial so I’m not really allowed anyways :frowning:

  1. No, instead you can have a smaller rigid body and use it as a parent for a larger object.
  2. Scaling should be avoided if possible, best to apply scale.
  3. The constraint pivot is at the origin of the constraint object. If you want to place it between objects use an emply (use the connect tool for convenience).
  4. That’s too vague to tell what’s goint on, make sure that the individual links are connected to each other and don’t connect them all to the first object.
  5. Don’t knon about that.

thanks that explains some stuff,
1, i think that could work for what i need.
2, unfortunately i need to animate the scale as part of the work, is there any way to fake the effect of an “animated” “active” rigid body, scaling up just prior to the “animated” property being turned off and rolling/bouncing into the physics world? I suppose i could use a pre scaled “proxy” object.
3, that’s a useful snippet of info, as a natural motion, euphoria user I was looking for a “pivot” XYZ input box but using empties seems much simpler…
4, the use of empties has all but irradicated this problem, so I assume it must have been an issue with having the constraints on the rigid bodies themselves and not separate (properly located) objects thus using the origin of the objects as a pivoting point.
5, that was always wishful thinking I suppose :D, but it would be extremely useful to me for performing puppeteering style animation in realtime.

Regarding the keyframe controller, you probably want to start a new thread for that. There are some examples around of blender animation being used to drive some physical servos via serial communication with an arduino microcontroller. It is done with a plug-in. This is more or less the reverse of what you want, but perhaps whoever wrote that plug-in has others or might be willing to help out.