fracture at sim time based on impact data (without prefracture)

[cgp]

Hi!

I need make fracture at sim time based on impact data (without prefracture). The point of impact is not known in advance, and I can't make a prefracture. I can do this during the simulation?

[pxptpw]

you can either add a voronoi fracture configure object after the rbd object for fracture during sim ,

or from the shelf you can select your object rbd object and then select your rbd object and make it breakable from the shelf button to start with and start tweaking your results

houdini help menu , nodes/dop/voronoifractureconfigureobject

Edited September 1, 2018 by pxptpw

[cgp]

Thanks, pxptpw.

Voronoi is more suitable for glass, stone, etc.  But what if I need custom cut lines (long, curved) for my plastic object?

[StepbyStepVFX]

Hi,

I think you should look at how the default shelf tool is making object breakable during the sim : the difficult part is to take off the object from the sim and replace it by a bunch of packed objects (in this case coming from a Voronoi fracture node, using the impact data to distribute the points of fractures). I personally don’t like the voronoi configure object as I have found it sometimes very unstable, with sim times increasing tremendously (even limiting drastically the number of objects created, avoiding very small ones etc.). I really prefer to control the fracture process.

If you don’t like the way Voronoi is fracturing objects, you can still use the same overall setup but replace the voronoi node by another setup to fracture an object. I am thinking for example using Booleans as cutters : you prepare a bunch of grids, all rotated randomly, with a mountain SOP to create sexy fractures shapes, and you instance this bunch of grids on the point issued from impact (you can extract the data impact information), use a Boolean as cutter to break your object with a pre-setup shape, and inject that into your simulation at the time of impact. This should give you lots of control on the shape of fractures of your object, without knowing beforehand where the impact will happen.

By the way, from the references you gave us (the pictures of deformed bumpers of cars), I would say that maybe a FEM sim could give more accurate results rather than breaking an object into smaller chunks of rigid objects (except if you use that to drive the deformation ?).

But once again, have a look to the shelf tool to make object breakable, and see the most difficult part which is how to replace one object in the sim by a bunch of new packed objects.

Hope that can helps you.

 

Edited September 1, 2018 by StepbyStepVFX

[cgp]

Thanks, StepbyStepVFX

I was try to realize your idea. It is not clear how to control the type of colliders (compound for pieces with holes).
Collisions work with bugs, penetrations. I am trying to fix it...

 

 

fracture_test.hip

Edited September 1, 2018 by cgp

[Atom]

Quote

The point of impact is not known in advance

You can do this in a two-step process. Use one simulation to collect impact points so that they exist throughout all of time. Then use another simulation to generate the fracture from those supplied points. The fracture is glued together. Activate the fracture by breaking glue bonds based upon proximity to collisions.

This video shows a way to set this up.

 

Edited September 4, 2018 by Atom

[Jesper Rahlff]

I could probably use this concept to get you started: