Is there a way to explode your RBD objects using interpenetration?

[magneto]

Hi,

I remember Houdini doing this before but now it seems like the objects do not explode when they are interpenetrating. I assume this is fixed now? I was not keeping track of RBD changes so perhaps someone who does would know more about it?

If you want a similar past behaviour, how would you achieve it? Should I simulate it using the older version of Houdini and save the results on disk, then load into the latest version?

I am not very experienced in RBDs so maybe this is an uncommon thing.

Thanks

[FR3D]

am not sure if i understand but you could use metaballs to blow up an object.

i remember in c4d i use to insert a static sphere in an fractured object to create the first impule(if that is what you are talking about).

here is a simple file using metaball

magnet force.hipnc

[magneto]

Thanks FR3D, that's a very interesting technique.

I was mainly talking about how the previous RBD solver was exploding the pieces if they were interpenetrating each other.

Btw do you know if you would be able to modify your setup so the explosions were timed? For example metaball 1 explodes on frame 10, metaball explodes on frame 20, etc?

[substep]

when I turn geometry representation to "as is" on the RBD fracture object, or turn down the collision padding, and also turn off "split impulse" on the rbd solver or some combination of the above, I get what i think your mentioning.

Edited August 17, 2013 by substep

[cwhite]

Thanks FR3D, that's a very interesting technique.

I was mainly talking about how the previous RBD solver was exploding the pieces if they were interpenetrating each other.

Btw do you know if you would be able to modify your setup so the explosions were timed? For example metaball 1 explodes on frame 10, metaball explodes on frame 20, etc?

You can put an expression in the Magnet Force's "Activation" field (such as $F == 10) to produce a timed explosion.

To answer your original question, the Bullet solver in 12.5 detects initially interpenetrating objects and prevents the Bullet engine from forcing them apart in an explosive manner.

Edited August 17, 2013 by cwhite

[magneto]

Thanks guys.

@substep: I did what you said but it still didn't explode when using Bullet or RBD. I also tried turning on split impulse and setting the threshold to -0.0001 but still the same result.

@cwhite: Gotcha, that's what I was wondering. So I guess there is no way to mimic this behaviour?

[cwhite]

@cwhite: Gotcha, that's what I was wondering. So I guess there is no way to mimic this behaviour?

There's no option to turn off the Bullet Solver's handling of initially interpenetrating objects, but you should be able to produce a similar behaviour using something like what FR3D suggested.

[magneto]

Thanks cwhite, that makes sense. I satisfied my curiosity now

[mawi]

Btw do you know if you would be able to modify your setup so the explosions were timed? For example metaball 1 explodes on frame 10, metaball explodes on frame 20, etc?

Animate the metaball source and set the SOP Geometery-DOP to "set always".

magnetforceAnim.hipnc

[magneto]

Thanks mawi, great trick

[FR3D]

sorry i didnt answer ,i didn't come back early enough.

anyway mawi got it for you