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cracking a ground


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  • 5 weeks later...



Doing a setup like this in one go will guarantee you getting stuck in tweaking hell, so you'd split it up and do it in "layers". What you split into layers and in what order you simulate it depends on the scene, but here's an example based on the clip you linked to. And for every step here, you'd of course bake the animation/simulation for the previous layer. :)


First you set up your foundation for the ground cracking, moving, be it animation or simulation.


Next you simulate the secondary effects for the edges, etc..


Now you simulate the house on top of that setup.


Finally you simulate additional objects like vegetation and such.

Edited by Farmfield
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Ive been doing this kind of thing at work! I was having difficulty figuring it out as well, I ended up going in the reverse direction of what farmfield said. Although his way is more logical and would work great too! However I found it really difficult to figure out how to simulate the ground falling from changing geometry thats being cracked.


My process was


Make curves for the cracks

Curves activate ground pieces to fall

Convert it to VDB

Convert curves to geo and convert them to VDB

vdb combine and subtract them to create the cracks in the already simulated ground

Convert VDB with using the original geo as the second input so you can keep the sharp features

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Hehe, how can you do that in reverse? The ground movement is what drives the house tearing apart, so you really can't do that backwards, unless I missed a workaround for that type of thing in some temporal mechanics course back in the day... :D


So the curve will create both the cracking and the ground falling down right? Attribute transfer from curve to ground controls the activation of pieces, so you do a certain width transfer and those pieces will fall down. Then that curve is what creates the crack in the geo, offset it by a few frames so the cracking starts first and there you go!


I know it makes no sense real world wise lol. But even with the house thing, I just mean do ALL the simulations first based off curves and then use the same curves just way thinner to crack at the last stage. 

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For the ground breaking, I would go for a non simulated setup as in a real world situation, that's likely something the supervisor/producer/director will want to have complete control over, so I'd go for a map based approach for the growing cracks and for the main pieces I would animate manually. Then I'd do a separate secondary simulation for the crack center and finally a sim for pieces breaking off the edges. 


And I'd have that completely set up, simmed and baked out before I got started on the house, vegetation, etc...

Edited by Farmfield
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