Dear forum users,

I'm trying to break a relatively thin box with the “make breakable” function in the apprentice edition of Houdini 12. Sadly though, I am running into an issue (or limitation?)

The box stops breaking under a certain thinness. I've attached the project file. It contains an extruded grid (the box that needs to break), made breakable and a small box that's made static. If you play the simulation, the box doesn't break. However, if you dive inside the box and change the Z value of the polyextrude to 1.2 (that's .1 higher) and run the simulation again, it will break.

(a regular box and changing the height instead of a polyextrude gives the same result)

I thought it had something to do with the minimum volume within the fractureparms settings within the Autodopnetwork. However, I can change it as low and as high as I want, but nothing makes it break at a height that is lower than 1.2! Neither do any of the other settings, including density and impact radius.

I've also tried changing the minimum piece volume setting inside the fracture tab of the rigidbodysolver to no avail. It just refuses to break under that thickness! And it needs to be even thinner than 1.1!

I'm wondering if this is just a limitation of the solver, or if I am missing something, because I can imagine it not handling flat planes very well, but the box still has a reasonable depth.

Thanks in advance,
Curb

Maybe it is your answer !

Yes when your Dynamic Engine is set to RBD Engine , you must change Volume Collision parameters regard to thickness !

So why you don't use Bullet Engine ?
It's so simple and faster than RBD for this point !

To do that just set Solver Engine to Bullet in the rigidbodysolver1(Rigid Body Solver) and change Bullet's parameters in the window(RBD Object) if you like !

I did that in attached file for you

Joker386
Maybe it is your answer !

Yes when your Dynamic Engine is set to RBD Engine , you must change Volume Collision parameters regard to thickness !

So why you don't use Bullet Engine ?
It's so simple and faster than RBD for this point !

To do that just set Solver Engine to Bullet in the rigidbodysolver1(Rigid Body Solver) and change Bullet's parameters in the window(RBD Object) if you like !

I did that in attached file for you

i see this project file it's very good like always but i have another example that in this time cube fall on the static grid.
i use bullet and make breakable tools but in this case it's don't work well!!!
but i have question:
if we do this sim with RBD Engine, how can we solve problem in collision moment?because of cube fracture one frame after hitting the grid!!!
i use more substep but with bounce 0 for cube, still i get some bounce for that!!!
so make breakable work well with RBD Engine but how should we use substep to get clean result for collision moment?
i sent bullet engine problem for support team and they said me in H14 we fix this type of problem.
thanks.

About Fracture with Bullet engine , I made some little changes on your project to achieve better result and I think this is good now , But please note that increasing substep is not good always (as I said before) :!:

Also to prevent moving pieces through the grid , you can extrude your grid even with Terrain Object !!!
And you should Set Geometry Representation to Convex Hull too.
Just check attached file.

About your second problem (Collision moment) , the DOP Breakable Object need some little time for computing fractured pieces , So if you fracture your object manually , then your object will break exactly on hitting Time.

So you can fracture your geometry with Voronoi Fracture SOP , then use Glue RBD instead of RBD Fracture .(see Houdini Help)
:wink:

thanks and thanks again you give me best answer.
but i have another question:
what's different between sub steps in DOP network and sub steps in RBD or Bullet engine or even pyro solver?
Thanks.

NimaNolan
thanks and thanks again you give me best answer.
but i have another question:
what's different between sub steps in DOP network and sub steps in RBD or Bullet engine or even pyro solver?
Thanks.

Substep in the AutoDopNetwork is a global substep for all of the Dynamically simulation , But we can increase Substep for just specify solver with it's own substep :wink:

Also You can learn some useful basic things about Dynamics in this page :

http://www.sidefx.com/docs/houdini13.0/dyno/top10_basics [sidefx.com]

thanks you are one of the best friend for me.:wink:
i will read this line to line.
thanks again.

NimaNolan
thanks you are one of the best friend for me.:wink:
i will read this line to line.
thanks again.

:wink: