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I've looked at various similar questions but ...
a) don't quite understand and
b) they were for older versions of blender.

I'm now on Blender 3.5

I am doing a Rube Golberg machine. First part is a ball rolling down shelves and into a basketball hoop which i've done wiht rigid body. Because it's finally worked i've baked it for frames 1-300 so it doesn't magically stop working. I now want the ball to carry on it's journey and it's going to knock some other things down etc. Can i bake a 2nd sequence of events in the same blender file?

I think i've read somethings about different domains and compositing but if someone could explain in a simpler way that would be brilliant.

Thanks Richard

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  • $\begingroup$ If you want the same object to continue its course you'll need to enable its Animated option, then bake again $\endgroup$
    – moonboots
    Nov 18, 2023 at 8:50
  • $\begingroup$ but that would be "hand animated" as opposed to adding rigid body to any other objects after that? I've found that if i now add other objects to the scene, they interfere with the physics of the original objects (even though they're nowhere near eachother in the scene!!) $\endgroup$ Nov 18, 2023 at 8:53
  • $\begingroup$ Could you please show an example of what you want, as simple as possible, it would make things clearer? $\endgroup$
    – moonboots
    Nov 18, 2023 at 8:58

2 Answers 2

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If you think about it, what baking rigid bodies mean and what the animated checkbox does, you should be able to answer your question yourself.

Baking a rigid body means:

  1. Blender creates keyframes
  2. Blender removes the rigid body

The animated (in rigid body settings of the object) checkbox (checked) means:

  1. The object is still part of the rigid body simulation
  2. The object won't move at all if you don't keyframe it

The animated checkbox (unchecked) means:

  1. Blender "takes" the "velocity" (animated keyframes for location before) of the object and animates the object in its simulation

So if you want an object to be a rigid body after you baked it so that other objects react to it, you have to add the rigid body again and check animated. But be aware that even if it now e.g. crashes against another ball and this ball will move (if it has rigid body) your animated ball will just continue its speed without any effect to the collision because now it only has keyframes.

Note: There is never a "in-between" state for Blender. Either it is animated (it moves via keyframes) or Blender calculates rigid body simulation. But yes, you can change that every frame if you like.

For longer rigid body simulations you would "normally" make copies of all rigid bodies e.g. after 300 frames because you don't wanna start the simulation always from frame 0. So you "bake" all rigid bodies, then copy them, give them all rigid bodies again and check animated on frame 300 and uncheck animated on frame 301.

If you mean the baking of the rigid body world under "cache": AFAIK you can only bake it once.

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    $\begingroup$ I think this is the clearest explanation! thank you so much. Can i just check that i've got it right in my head. I was at frame 1: Added ball and floor etc with rigid body and collisions etc, animated tick box was unchecked. Pressed Play and it simulated the movement etc BUT each stage of the movement is not assigned to a specific keyframe at this stage. At frame 300. i stopped the simulation and baked it. This then stopped the stimulation and essentially locked in each location/rotation etc to a specific keyframe. [like it was almost hand animated] $\endgroup$ Nov 18, 2023 at 12:54
  • $\begingroup$ So now, at frame 301 i check the "animated" box and it restores the rigid body world settings to the ball at surfaces but the ball will only move to where i have animated it to move? $\endgroup$ Nov 18, 2023 at 13:01
  • $\begingroup$ @Chris ... Oh +1 ... now I see I wasted my few hours ... previously your answer confused me, especially first two points, I thought you mixed bake types ... now I realised I was working on version 3.4 ... but 3.6.5 LTS has the operator you mentioned Bake to Keyframes (I'm not sure about OP's 3.5) .... Grrr $\endgroup$
    – vklidu
    Nov 18, 2023 at 17:04
  • $\begingroup$ @BuddingBlenderer: yes, so if you wanna have a start velocity you have to keyframe location 2 times so that Blender takes it into account. And of course you have to keyframe checked animated and later unchecked animated. $\endgroup$
    – Chris
    Nov 18, 2023 at 17:57
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    $\begingroup$ @Chris ... old, slow ... ? :) WIth all the gifs, screens, optimisations, structured text, plus other approaches I wanted to try ... yes a few hours :) My bad. Time to upgrade my home machine :) $\endgroup$
    – vklidu
    Nov 21, 2023 at 8:49
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In this example I split sim into two parts ...

Frames 001-050

  • Scene Properties > Rigid Body World > Cache set Simulation Start 1 / End 50 and Bake cache

enter image description here

  • Select object you want to keep baked as it is and go to 3DView > Object > Animation (or search for) Bake Action operator and enable Visual Keying at frame range 1-50 (it will generate keyframes per each frame).

enter image description here

Frames 051-100

  • Scene Properties > Rigid Body World > Cache set Simulation Start 51 / End 100 and press Delete All Bake
  • for object with keyframed simulation go to Physics Properties > Rigig Body > Settings, check Animated and press "I" to create a keyframe for this checkbox at frame 50 ... go to frame 51 uncheck Animated and create another keyframe for this checkbox

enter image description here

enter image description here

  • now just repeat Bake Cache and Bake Action for these frames as described for first frame sequence

enter image description here

Notes:

  • You can simplify the process bellow by baking entire sim cache and use Bake Action operator for a frame range you set in popup window.
  • Your last paragraph "I think i've read somethings about different domains and compositing ... " Domains are related to fluid physics (volume, liquid) there is cache stored into individual files per frame (can be also saved externaly) and can be combined in various ways since only naming convention matters. Compositing is also possible, but it is based od rendered images.*
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