Thanks in advance for any help on this. Just playing around with Rigid Body behavior based off/extended from this tutorial, https://www.youtube.com/watch?v=-4uFt0m5I-U

I keep tweaking and tweaking the Rigid Body properties of the 'earths' and the sandbox and just can't seem to get them right, I assume because I really don't understand what each control does.

I want to simply drop these 'earths' into the sandbox and have them bounce around a bit, roll around a little and settle into the low spots, in a natural looking way, perhaps what you would expect if god were playing marbles with planets.

But they either immediately explode outward in all directions too quickly escaping the sandbox OR they descend very slowly and settle too quickly. I've made my test blend smaller and simpler for faster bakes and retries but the iterative process of struggling to find the right settings is time consuming and frustrating. I assume that if I understand the Rigid Body Controls better I can make better decisions -but how to learn them? I think that Friction and Bounciness are probably obvious and while I think I understand margin, I suspect I don't. I keep playing with Friction, Bounciness, Margin, Damping Translation and Rotation, mostly on the earths but also on the sandbox but I just never can get what I am trying for.

In this case I am not looking for help on the right settings, I am looking for help to understand the settings so I can reduce the amount of experimentation/iterations required to find settings I am happy with and when parts of the sim start working as desired I will understand what to change next and what to leave alone. Right now it's all just a crap shoot.

Start Image start -

Initial separation separating in all directions

Sandbox Physics sandbox physics


1 Answer 1


I just tried something similar and it worked OK, I'm guessing your spheres are too close / touching on the initial frame. This will upset things. Here's my result- https://www.dropbox.com/s/cdtnwukjwakg6kc/RigidSpheres.mp4?dl=0

And here's the scene- https://www.dropbox.com/s/aw6pmq5tmis0kee/RigidSpheres.blend?dl=0

If you move my spheres so they're touching/intersecting they repel each other as they start to fall.

Cheers Mark

  • $\begingroup$ Thanks Mark - I have recently learned this too, even if they start out NOT touching, they can fall into each other and explode if the physics are not consistent across the set. The key seems to be to make sure that they don't touch and don't touch too quickly or too much as they fall (due to different physics). $\endgroup$
    – Jon
    Jan 13, 2020 at 11:44

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