Is it me or are dynamics still based a little bit on voodoo?


So I have an object with a dynamics tag inside of a null to just react when the null moves or rotates with a little jiggle or delay. Works great as long as the animation is short, like 6 seconds. I extended the animation to 30 seconds and it seems the further along the animation is, it breaks. The dynamics seem to work in the viewport, but break during rendering, and then it will just break altogether. Caching does not seem to help once it’s broken. I can adjust the timeline so it bookends only when the dynamics object is in view, cache it, and then it works again.

As always, it could be I just don’t understand it deeply enough, but dang.


Are your project FPS and your render FPS the same?

If they’re different the dynamics will offset over time.


when you have problems with dynamics it is always a good idea to try and crank up the values for steps and max iterations quite a bit. depending on the amount of objects you can even go to values like 50 and 200.

but even then the dynamics stay a bit unpredictable.

best regards


A dynamic object stops being dynamic if it hasn’t moved for about 2 seconds. You can disable this by setting linear and angular threshold to 0. A collision or force is supposed to ‘wake up’ a switched off dynamic object , but this sometimes does not work.

This behaviour is designed to stop dropped coins etc spinning forever, and can be the reason dynamics breaks after a period of time has elapsed.


Thanks for replies, guys!

They are identical at 24 fps.


Excellent, that’s at least a starting point and good rule of thumb. :slight_smile:


Hmmm. I do have a vibrate tag on the object as well, does that count? Just gives it some random motion instead of being static at any point, like you say. In the image it’s the little ball in the lower left.