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Color propagation drives fracture/cloth

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Hi guys !

I try to achieve this kind of effect : 

Inspired by the growth propagation of Ben Watts (picture below), I now wonder how to drive voronoi and RBD activation by color.

At 0.11 seconds I don't understand how his voronoid/scatter is drived so progressively... Mine is entirely fractured at first frame (I'v just smaller pieces along color progression). 
For the RBD activation I tried a lot of ways proposed here like use active value, sop solver in dop, attributes etc... But my object is directly under gravity, without distinction between pieces colored or not

Maybe some logic escape me but if someone can enlighten me, that would be great ! :)

Screenshot - 05022018 - 11:31:26 AM.png

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One trick really useful is to not use just one noise, but layer multiple noises one on top of another. Different frequencies and delaying them of a few frames works well. With just one gradient/noise is hard to get this effect of propagation.


Using the active attribute from SOP is the quickest option, I think. It needs to be a point attribute and you need to overwrite it every frame using "Overwrite attributes from SOP" in the RBD object so it checks if the piece should be active or not.

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You can definitely get some inspiration from this (I think the hipfile will be available today or tomorrow)

or this great written explanation by @PixelNinja


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Thanks guys for your quickly answer.

@Andrea: the effect of propagation is not a problem, I started with this tutorial (https://www.youtube.com/watch?v=euG933INMTk) and added some randomness. Looks really organic :)

But his simulation is drived by movement while mine is inanimate so I can't use his parameters...
Right now I dropped a wrangle with i@active = 1; after my colored points (deleted from other points to have only my growth) and an another wrangle with i@active = 0; after my packedprims and it's look better but somes pieces stay frozen.. I think this way is the best to go since I tried to set with color attribute in sop and geo context (with attribcreate and group) without success.

What I want is just than my color drives my rbd simulation. I think it's just an incomprehension of how set my active value between color points and fractured geometry. Pretty sure it's amateur mistakes aha. 

@Jesper: yeah, I watched his hipfile, and this way is a bit different but looks great. But maybe that will be more difficult to drive the cloth after with this setup? 
But method by PixelNinja looks really badass, I will try it too. 

Thanks both of you, if I still fight with my color I'll upload a file. That will be more efficient to show my problem. 

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Just a little review of my precedent message: so I was on the right way last time. Just need to tweak the distance threshold parameter of my attribute transfer in DOP to activate frozen pieces. That was effectively an amateur mistake. 

@Jesper: I followed the PixelNinja way for my cloth, it's outstanding !

Just a question now for my initial concept: in fact, elements need to disappear into dust/ash. 
I was thinking about a solution where pieces results from voronoi/cloth will become smaller until disappearing OR combine a blast/delete node to remove activated geo (while keeping a random number of it) with an emission of particle from this same group deleted to simulate a transformation in dust. I don't know if it's understandable...
The problem for these setups comes with creation of group along time (based on "age" of activation). My color spread already drives activation for all these things so maybe it can drive size or delete/emit particles with a delay?

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