rbd and softbodys

[bonassus]

I'm trying to understand what is possible in combining  rbd and softbody simulations. Or what the workflow should be to get a fractured object to break apart like in a rigid body sim but also be a bit squishy. Like how a pumpkin might break when dropped from 2 meters off the ground. I haven't been able to get this look with fem and fracturing as the individual pieces kind of stick together on impact and don't break apart the way rbd does. Is there a solution with the multi solver? or some implementation of the grain solver that i can't think of. if someone has a solution for this i would very much appreciate it if you shared it with me. 

thank you. 

B 

[chrisdunham95]

14 hours ago, bonassus said:

I'm trying to understand what is possible in combining  rbd and softbody simulations. Or what the workflow should be to get a fractured object to break apart like in a rigid body sim but also be a bit squishy. Like how a pumpkin might break when dropped from 2 meters off the ground. I haven't been able to get this look with fem and fracturing as the individual pieces kind of stick together on impact and don't break apart the way rbd does. Is there a solution with the multi solver? or some implementation of the grain solver that i can't think of. if someone has a solution for this i would very much appreciate it if you shared it with me. 

thank you. 

B 

I would personally run a RBD simulation get the results I want breaking/fracturing wise then run that through a soft body sim to add the extra wobble/jiggles or even fem perhaps.

OR Fem using the fracture within that to get the break apart - perhaps the best method especially for a pumpkin or something organic (if you do some research I'm pretty sure theirs various ways of controlling the breaking/fracturing within FEM but I'm not certain) - ill post a hip file perhaps when I get chance to take a look

Edited October 19, 2017 by chrisdunham95

[bonassus]

Thanks for the reply Chris. I'm struggling to figure out how to do this correctly. Allow me to describe explicitly what I think you are saying for your first suggestion. Run an RBD sim and cache the results. And then sim the cached geo as a granular solid? I assume that's what was meant by soft body sim (please excuse my ignorance). I have not been able to get this to work. I have attached a hip file softbodytest_grains.hiplc encase you are willing to take a look and possibly point me in the right direction. 

In the houdini docs in the shattering section under tips it says:

Quote

You can set up a hybrid simulation where you use voronoi fracturing to separate "large scale" pieces and then at a certain frame switch the geometry to solid objects. The best way to do this is to simulate the voronoi fracturing, cache the simulated geometry to disk, and then use the cached geometry and switch it to Solid objects at the given frame.

 http://www.sidefx.com/docs/houdini/dyno/shatter

This sounds like what i want to do. but i really don't understand how to set this up. I assume this means start the solid sim on the impact frame of the rbd. would this be done without gravity in the solid sim using the velocity from the rbd sim? Also the solid embed turns the fractured pieces into on tetmesh which wont do a good job of deforming embedded geo.  Is the the solution to use a loop to tetrahedralize each fractured piece and feed them separately into the sim? I'm obviously unclear about how this works and would appreciated any guidance. 

I have also attached my attempts at fem shattering and the rbd fem hybrid approach(neither of which work). I'm hoping you can give me some pointers to get the pieces to break apart. 

Thanks for any help.

 

softbodytest_fem.hiplc

softbodytest_grains.hiplc

softbodytest_rbd-fem.hiplc

[tamagochy]

You are can use switch constraint in rbd sim. And use hard constraints to fake soft body after first impact.

[bonassus]

6 hours ago, tamagochy said:

You are can use switch constraint in rbd sim. And use hard constraints to fake soft body after first impact.

Sounds promising. Any chance you could provide an example? 

thanks!

[fencer]

http://forums.odforce.net/topic/20691-realistic-dynamic-fracturing-with-bullet/

[bonassus]

17 minutes ago, fencer said:

http://forums.odforce.net/topic/20691-realistic-dynamic-fracturing-with-bullet/

Thanks for posting this. It looks like a great example of a bending/denting technique. Very interesting even if there is no explanation of how it was achieved.  What I'm after is a sim that is bouncy after breaking apart. 

Thanks for the reply

[fencer]

20 minutes ago, bonassus said:

Thanks for posting this. It looks like a great example of a bending/denting technique. Very interesting even if there is no explanation of how it was achieved.  What I'm after is a sim that is bouncy after breaking apart. 

Thanks for the reply

Look through the topic, there are some useful examples.