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I’m hoping to create a nice music driven animation, that shows an object ‘kicking’ into the air, a bit like a popcorn kernel popping, but in time with the music. What kind of approach would this involve? Physics? Gravity?

I have already experimented with baked F-curves to audio, but it's not quite right. I wondered if it was some kind of turning on/off of a force, to propel the object into the air, and letting it fall down/bounce, before propelling it again. All synced to the beat.

Any ideas much appreciated.

Thanks!

Had some good success with the 'popping plane' approach, using three objects:

  1. The pushed cube
  2. The pushing cube
  3. The floor

Just a single frame of pushing cube Z movement, after experimenting I just need a tiny amount.

I can hide the pushing cube. Boom.

enter image description here

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  • $\begingroup$ every force or even gravity can be turned on and off with keyframes so you can animate it. However I am not sure if physics is what you want if it is supposed to be controlled $\endgroup$
    – MikoCG
    Sep 17, 2021 at 11:38
  • $\begingroup$ Why do you need physics, do you need some kind of collisions between many objects? Otherwise, what you're asking is achieved by Z location defined by a simple curve that starts with a bezier point with a handle going vertically (so the curve is steep at the beginning), and ends with a point having a horizontal handle (so the velocity is lower and lower and gets to zero, then the reverse, with the object falling faster and faster. The curve points also have "Bounce" interpolation type, though I guess then you might indeed need physics for more elaborate movement at the end, based on shape. $\endgroup$
    – Markus von Broady
    Sep 17, 2021 at 11:59
  • $\begingroup$ Thanks everyone. $\endgroup$
    – jameslondon74
    Sep 17, 2021 at 12:18
  • $\begingroup$ I don't want to control the object when it's propelled into the air, I just want to propel it, and let gravity/rigid body physics take over. That's why I thought physics would be involved. So ideally, at each 'beat' in the music, I'd do something to propel the object vertically and let it fall and collide each time $\endgroup$
    – jameslondon74
    Sep 17, 2021 at 12:19
  • $\begingroup$ Possibly related: How can a force be applied not to the center of a rigid body object, but to one specific vertex of the object? $\endgroup$
    – Markus von Broady
    Sep 17, 2021 at 12:34

1 Answer 1

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Here's a semi-controllable manual but simple solution. Use a combination of Rigid Body Physics combined with an animated passive floor plane. The benefit is you have easy control of the speed and height of the object 'kick' by simply changing the floor plane keyframes. The downside is it requires some manual timing to the music.

  1. Add Rigid Body physics to the object.
  2. Add a floor plane with Rigid Body physics set to passive and check 'Animated'. (Disable render to hide.)
  3. Animate the floor plane location up and down to 'kick' the object up in time with the music.

enter image description here

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  • $\begingroup$ This is a nice idea worth trying, thank you. I could hide the popping floor plane, and add a visible floor plane for the floor. This also means I can keep the popping floor plane bumping to the music, constantly effecting all the other rigid body objects that are on top. In my mind, I'm wanting the same effect as flicking something in the air with your fingers, so this is kind of the same thing isn't it. $\endgroup$
    – jameslondon74
    Sep 17, 2021 at 14:43
  • $\begingroup$ Just trying it, it is a little fiddly. Is there a solution there I can use a force to literally push an object in a particular direction, and then turn that force off immediately afterwards? Sort of like a physics force cannon? $\endgroup$
    – jameslondon74
    Sep 17, 2021 at 14:51
  • $\begingroup$ You can use a force and I’ve done that before for animations, (eg animate the gravity direction)… but it’s actually harder to control than this way in my opinion. $\endgroup$
    – Dan
    Sep 18, 2021 at 0:38

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