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I've had this effect in my head for some time but still unable to think of a possible way to do it. For the sake of simplicity, would there be a practical (time-wise) way to create an effect where the letter A blows up (fractures) and then the pieces recombine to form the letter B?

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    $\begingroup$ You know, often CG is about faking effects. You could break the A in small pieces, tiny blocks, then make them move towards a basic B shape, and then fastly make a hidden real B shape become visible instead of the pieces. $\endgroup$ – m.ardito Dec 1 '15 at 10:29
  • $\begingroup$ Feel free to add that as an answer or a comment with further explanation, I'm not sure how you'd go about doing that. I fracture letter (mesh) A into small pieces, then how would they "get together" to fill a volume similar to the letter B? (which I could then fade into in post processing). $\endgroup$ – Leo Ervin Dec 1 '15 at 17:27
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Another way is morphing objects with Particle Systems

GIF

You can morph shapes of objects and even objects themselves (influnced by Explode modifier) with Keyed Particle Systems.

From wiki:

The particle paths of keyed particles are determined from the emitter to another particle system’s particles. This allows creation of chains of systems with keyed physics to create long strands or groovy moving particles.

You should only setup them in appropriate way so to make particles travel from one emitter to another.

Step 1: Add objects and assign "simple" particles systems

These systems don't do anything but providing particles needed for action. Because we need them to not emit in time, setup this system (as you can link to both objects the same) so to change Number of particles, Start and End time, Lifetime, Velocity.

Step 2: Add Keyed particle system

Add 2 different Keyed Particle systems - 1 per object. As in the gif above, first setup object on the left. Change Number, Start and End, Lifetime to the same values as for the "simple" particle system and set Velocity > Normal to something more than 1.

And the main, in Physics scroll select Keyed. Add 2 keyes (in both setups) and setup them in this way:

  • for object Sphere: - 1-st key: second ParticleSystem of the Suzanne (use slider in the bottom to select Particle System of the object); - 2-nd key: second ParticleSystem of the Sphere.

  • for object Suzanne: - 1-st key: second ParticleSystem of the Sphere; - 2-nd key: second ParticleSystem of the Suzanne.

(in example above I also changed timing in Time and Duration sliders so to make systems not interfere with each other, and materials transparency, in order not to see already broken object etc.)

Now, for both objects add Explode modifier, and move it to the bottom (under both particle systems). Choose Cut Edges for finer result.


Note that this way doesn't provide accurate result and it could be greatly enhanced. Particulalry, here are some disadvantages:

  1. Objects' topology means a lot for this to work. Particles will be emitted taking into account amount and distribution of them on the faces.

  2. Keyed Particles aren't affected by physics (so force fields, gravity and so on). Read more about it in this related question. In order to further improve such animation you may consider using 2 approaches:

    • using simple systems as keys in Keyed Particle System setup (it would involve a lot of cheating to make particles form initial objects)
    • using 3-rd object and 3-rd Keyed Particle system which shold represent "falling particles down" (if simulating gravity).

Although it could be a beginning for some effects.

(note that stripdown version of file is linked; it includes morphing objects, their setup, ground plane and light).


Credits for particle systems setup:

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  • $\begingroup$ good answer. I know about keyed particles but I didn't get the part about using Masks. $\endgroup$ – Leo Ervin Dec 1 '15 at 22:53
  • $\begingroup$ This intended to be starting point for creating workarounds for that unpleasent result in the end. You could duplicate objects, add Object Index for both copies, make copies invisible and in compositing make their alpha masks influence on each other. Thus when particles of the object1 fly over object2, the last one should be revealed. I didin't test that though. $\endgroup$ – Mr Zak Dec 1 '15 at 23:02
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I am quickly adding what I had in mind: mine was just a suggestion, never did anything similar.

You could use a fracture addon (there are 2 in 2.76, I heard of specific builds, too) to obtain several tiny blocks from "A" object, then

  • select all them, and
  • insert keyframes (for their starting point).
  • then, choose a "middle point" between "A" and "B" objects,
  • move all the tiny blocks there, and move to some 40 frames later
  • then key frame them all, there

    then, maybe do "the opposite" for the "B" object

  • move to the "final" frame, maybe other 40 frames later

  • fracture the "B" object with similar ending blocks count/size,
  • keyframe all the "B" blocks in their "final" position
  • then go to the frame of the "middle point" chosen before
  • now move the "B" block just "near" the previous "A" blocks,
  • then key frame the new "middle" position for the "B" blocks.

then you should find a way to hide "A" blocks when they should be replaced by "B" blocks, maybe a high moving speed will help to mask things...

in the end, playing the sequence from 1 to 80, it you should see "A" crash into small pieces moving to a middle point, and then go to the "B" ending point... Ill try to create some simple example, and add it later, maybe in the meanwhile you find some even better way...

[edit] ok, here is a sample .blend, of course the various objects visibility is still to animate, but the general idea is in this file.

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