Hello there,
Apologies if this question has been asked before I’m not sure what terminology to use here.
Essentially I’m making an animation of a bottle being smashed using the Cell Fracture Addon. Originally I had this bottle at a realistic size of about 20 cm, but the Cell Fracture process struggled with that size and all the little bits came out weird. So I scaled the entire scene up by a factor of ten, so now according to the scene world this is a 2 meter bottle, but the fracturing works.
The animation is too slow now, because of course everything’s massive, but I’m unsure how to adjust the speed.
I found a forum on filmmaking that stated that when doing physical models such as an exploding house, the framerate needs to be increased by a factor that is the square root of the model scale, so instead of shooting at 24 fps for a 1:10 model you shoot at 24 x sqtr(10) aka 24 x 3.162= 76 (kinda)
So I assumed the rigid bbody World speed has to be 3.162. But It looks off. am I doing maths wrong. Should I rather change something with the gravity setting?
Thanks in advance
So scale it back down again now the fracturing is done.
Have you set the Mass? Object Menu > Rigid Body > Calculate Mass > Try both the solid and broken glass settings…
Set the mass then tweak speed and gravity.
Scaling was kind of a pain because of certain location keyframes. Is there an easy way to scale that accomodates for that?
Uhhh… Probably, but my mind is blank at the moment… 
… long day.
not a pro, but i think the rule in film making was about practical effects, they used to make smaller than scale miniatures and the change in frame rate is to have to best motion blur based on the fact that they will slow the footage or speed it up
in your case, if you scaled your bottle by 10 revert that in the world speed and it must be a factor of 10. or 0.1 not sure which direction you should go
and yes mass and gravity can change accordingly too