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pre-fracture vs dynamic fratured

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Jimbo55
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Hello Houdini users,
Is there a way to bring in your per-fractured object into dops from Sops at the point of impact? The attached images shows the problems with bringing in pre-fractured objects. Before it has hit anything you can tell that it is already shatter.
I want to make a object be RBD like normal(un-fractured) but tell a object that once it has hit something, (in dops) to shatter exactly like the geo has been prefactured in Sops.

the ball on the left is a RBD object that has been made breakable(Via the make breakable tab)
The ball on the right is a object that has been prefractured and then brought into dops.

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Balls_Breck_Glass28.png (457.3 KB)
Balls_Breck_Glass25.png (428.5 KB)

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Jimbo55
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Here is a Hip file with what I am trying to do.

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Pre_Brecking_Test_v01.3.hipnc (1.9 MB)

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rafaels
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You can use a switch SOP to alternate between a whole object and the pre-fractured object upon impact.
You'll can animate the switch by hand, which can be a fast solution for simple cases, OR you can create a network logic to detect the first impact and procedurally switch the geometry in that case. The second option is a bit more elaborate, but not too difficult and you can find examples of that in the forum.

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Jimbo55
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Thanks rafaels,
I have tried to use a switch sop but with no luck. When I make the switch at impact the geo disappears. Could you point me to a forum post where they mention how to do it? Thanks.
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zdimaria
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the idea is to run the sim with the prefractured object all the way. you then use a switch sop to switch between the cached out prefractured sim and a cached out non fractured sim.
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Jimbo55
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Thanks zdimaria for the clarification. That seems to have worked. A video is enclosed showing that workflow.

Is there not a way to do it on DOPS before writing it to disk? Thanks for all your help.

Attachments:
Solid_To_Pre_Fracture.mov (4.9 MB)

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rafaels
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If you start with the solid sphere in DOPs and then use the shelf tool “Make breakable” it does dynamically fracture for you in DOPs. You lose a bit of control over the look of the fracture, but if might work for you.

Cheers
Toronto - ON
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Jimbo55
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Thanks rafaels. that is the way ive been use to doing it. Since experiencing the possible power of pre-fracturing I have been curious if there was a way to take that voronoi fracture configure object1 in Dops, and at the moment of impact have that node look at the voronoifracture sop node and fracture the object identically from that node.
Digital Tutors has a tutorial that kind of does what I'm talking about.

http://www.digitaltutors.com/11/training.php?vid=7098&autoplay=1 [digitaltutors.com]

His approach is to copy the parameters over from the voronoifracture sop into the
voronoi fracture configure object Dop. It gets close to what one has in Sops but its not exact.

Does this make since? Thanks again.
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rafaels
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Yes, the key with dynamic fracturing is that Houdini looks at where the impact occurs and seeds some voronoi fracture points around that area. You'll probably get different chunks every time because it'll depend on the impact location.
If you really want to have control of the chunks and all then you have to kind of scratch the dynamic fracturing workflow and go for your current workflow.
Alternatively you can set up dynamic fracture on top of your pre-fractured pieces for extra randomness…

Cheers
Toronto - ON
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“As technology advances, the rendering time remains constant.”
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Jimbo55
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Ok good to know. Thanks Rafaels and zdimaria! You have been a huge help.
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