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FrenchHawk

Cutting system [perhaps FEM working]

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Hi there, I do some R&D for my team graduation movie, dealing with a bunch of food slicing, cutting with knifes, wire cutting and viscosity involved.

I would need some help with the cutting part. The idea is to cut geometry (imported if possible) into multiple SOFT pieces.
For the "juice" in the food it's already ok, but I'm having hard times with the slicing.
 

I'm new to this side of houdini. Trying to find examples or trainings, but aside from Artem Smirnov and Steven Knipping videos (light on houdini nodes explanations), I can't find a way to have at least their results.
What do you think is the best approach to the problem ?

 

https://vimeo.com/79221859
https://vimeo.com/81969172

 

Edited by FrenchHawk

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There are lots of options, such as CMIVFX, or FXPHD, and SideFX themselves has a pretty good collection of training.  But for getting started in Houdini Peter Quint has one of the best tutorial collections: https://vimeo.com/user2030228

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Thanks Sierra62, but finding tutorials is not a tough job, I was talking about a soft geometry slicing system.
Saddly there isn't any tut about it on this Peter Quint collection.

Edited by FrenchHawk

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Sadly there isn't much out there for FEM, you could try using the fracturing for the cut, but it it can be unpredictable and slow.  However the easiest way to do it may be to pre-cut all the pieces before you sim then animate the pieces activation so the soft body sim will interact with the knife but it won't need to worry about really high res FEM sims to get it done. By pre-cutting you will get cleaner shapes and have more control over the final product.  

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So I'm pretty sure someone put out a hip a while back, I was even sure I had downloaded it, though I looked through my demo-file folders now and couldn't find it...

 

But setting something like that up isn't overly complicated, if you create your setup and set the piece to be sliced to be a fracture object, then you can move the create_fractured_groups and rest nodes into a Solver node, then add some kind of slicing setup before that, using volume break or whatever, even the cookie node could probably work, either animated or using a switch and an expression...

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Wasn't there a Pixar paper on this as well? From their work on Ratatouille. Might be something to look into.

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Damn that hip file could have com handy. Still trying to work it out on my side, don't worry.

Yes, I have read the Pixar Paper. Theorically, I get it. It's getting their toughts on H14 as a solver which is pretty tough.

Edited by FrenchHawk

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Hi, Fabien. The system in my video is very old and not valid nowadays. I think now it can be done much more easily with a sort of dynamc fracturing system. I would try using packed prims with bullet  in your case (I use it to have a fast fake of FEM soft body behaviour). Please look at this thread for the reference on fracturing packed prims at the sim time, and also have a look on the attached video for faking FEM with a bullet.

Edited by Artem Smirnov

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I have assembled a simple example for you to start with. For soft body effects you should push it a bit further.

 

Edit. and another example of cutting thin soft body sheets. It is even more simple. 

cuttingSys_1_.hip

cuttingSys_2_.hip

Edited by Artem Smirnov
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great stuff artem , thanks for sharing those very informative hip ...

 

i didn't know that you could use wire solver as a cloth/soft bodie tools ... for an obscur reason i always thought it was for curves only ... :blush: 

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I have assembled a simple example for you to start with. For soft body effects you should push it a bit further.

 

Edit. and another example of cutting thin soft body sheets. It is even more simple. 

WOW, That awsome

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I only checked the second file, it works fine. I have to dive into it later, looks great though. Nice work Artem :)

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I've wondered How to cut geo, wow.... God bless you.

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