Rigid Bodies working incorrectly

Hello, everyone:

I apologize for the extremely vague title. However, I’ve been having this issue for a while now and it’s gotten quite frustrating.

You see, I’m trying to create some kind of physics for the hair I have in my model by using rigid bodies and empties. But whenever I add more than one pair of the chains of rigid bodies and empties, everything just falls apart. I’m sorry if this seems very confusing, but I do have a few links to images and files that will (hopefully) help.

Gif #1, of the rigid bodies working as they should:

Gif #2, of the rigid bodies working incorrectly once I insert more than one pair:

And here is the blender file itself:
https://uploadfiles.io/2c3fm (I apologize for the large file as well)

And last, if this helps any, I’m using this tutorial as a guide:

Thank you for reading this incredibly long post. If anyone can help, I would be very much grateful. :slight_smile:

I too am struggling to make rigid bodies behave properly. I’m trying to make some animations using models from the MMD community. MMD is a Japanese animation program, but it’s not as sophisticated as Blender. MMD has it’s own rigid body system, but that’s the extent of its physics simulation, so character models use rigid bodies basically for any loose parts (hair, clothing, soft tissue).
Daniel Kreuter’s videos make me think the same effect can be achieved in Blender. Without more info or a blend file I’m not sure what to suggest.
The basic troubleshooting checklist I’ve put together from many (many many) scattered videos and posts is:

  1. Apply scale to your rigid body meshes, so that “Scale” values in the properties pane all say 1.0.
  2. Increase Rigid Body World Steps per Second and Solver Iterations under Scene properties.
  3. Scale all the objects in your scene to be approximately 1 Blender unit at minumum. The scene unit scale seems to be cosmetic only; the rigid body physics simulation assumes that 1 Blender unit = 1 meter, no matter what your Scene unit scale is. The rigid body sim breaks down at ~0.10 meters from my own tests, and the official documentation recommends no object have a “radius” less than 0.2 meters. (Or, I assume, no edge less than 0.2 m for non-circular meshes. Documentation on the rigid body sim is woefully lacking.)
  4. Set the rigid body world “speed” to be the square root of your scene unit scale. If the scene is scaled up by 2.0, increase speed to ~1.414. If scale is 100, increase speed to 10, etc.)
  5. Use more primitive rigid body shapes for your collision meshes over convex hull or mesh. Use Box or Sphere etc. if you can get away with it. Use convex hull if necessary, and use “mesh” only if absolutely necessary with a concave mesh.
  6. It’s better to use three-dimensional shapes for all rigid body objects. Flat planes are more likely to have collision errors. Using a flat cube for a floor is favored over a plane mesh. (It looks like you don’t have a floor though, so idk.)
  7. Make sure all rigid body object origins are at center of mass for proper simulation.\
  8. Make sure no rigid body objects are intersecting at the starting frame of the RB sim’s frame range.

Best of luck! Blender’s rigid body physics have a lot of poorly documented (or not documented at all) limitations, so unfortunately using them effectively has predominantly been a massive trial-and-error effort on the part of the end users.