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Shatter complex dynamic object after collision with floor

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George Lazarev
Shatter complex dynamic object after collision with floor
on Sep 22, 2016 at 5:34:48 pm

Heya! So I have this piano made of 200 pieces and my idea was to drop it from height but i realized it begins to fall apart before even colliding with floor:



And then it reached the floor and shatters even more:



Which looks odd and not what i thought of and somehow i did find a way to keep it together just until the collision.

Naturally, to make it dynamic i had to apply the rigid body tag to each of 200 pieces, cos it didn't work with parent null and if i connected these pieces into one object and made it dynamic, then it wouldn't shatter. Thrausi is not an option as i want to capture buttons falling apart and i've seen on youtube thrausi falls apart before the collision as well. Any help is appreciated.


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Brian Jones
Re: Shatter complex dynamic object after collision with floor
on Sep 22, 2016 at 7:35:55 pm

with Thrausi type objects (a number objects in a Fracture as Thrausi does) to get something to fall dynamics have to be on but if it's many pieces you have to leave dynamics on but turn off self collision until the first collision of the group with something. Otherwise the self collisions keep separating everything too early as you have seen. Since you have everything with it's own tag that won't work since turning off self collisions doesn't do anything useful.

Place your piano objects in a Fracture object and apply an xpresso tag and feed the fracture object to a Dynamics Collision node as one of the objects then pass the Count from that node to the Dynamics tag/Self Collisions port. That detects the Fracture's (and by extension any part of the piano) collision with anything in the scene that has a dynamics tag but isn't the fracture itself since the other Object port is left empty.
The collision count stays zero until a collision happens so it can be passed directly to the Self Collisions of the fracture's (the piano) dynamics tag and turns it on with the first collision since the Self Collision port is boole and is expecting 0 for 'off' and 1 for 'on'. Fortunately when they were designing xpresso they let you put numbers higher than 1 in (in this case more collisions) and it still interprets it as a 1 so the self collisions stay on and it works like it should.

10610_stopprecollisionseparation.c4d.zip


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George Lazarev
Re: Shatter complex dynamic object after collision with floor
on Jan 31, 2017 at 12:15:37 pm

Thank you so much only recently i got to play around with it, apparently its nearly impossible to get a perfect animation as some piece would spin on nearly light speeds, is there a way to bake it all to keyframes? None i googled or knew worked, functions > bake doesnt seem to work, i guess the problem is fracture and ive no idea how to work with that..


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Brian Jones
Re: Shatter complex dynamic object after collision with floor
on Jan 31, 2017 at 3:28:30 pm
Last Edited By Brian Jones on Jan 31, 2017 at 3:30:04 pm

stopping overly-dynamic dynamics is done by changing settings in the dynamics tags. It's very easy to have too much energy in the system. Lower the bounce, increase friction (where appropriate), increase Linear and Angular Damping. There is a good bit in the help in Dynamics/Tips and Tricks/The Party's Over - it talks about stuff that won't stay still afterwards but it applies to your situation too. I would think higher Angular Damping on the high speed spinning parts would be a start.


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George Lazarev
Re: Shatter complex dynamic object after collision with floor
on Feb 1, 2017 at 5:28:01 am

I understand, but it seems impossible to reduce it without damage to the animation (in my case it looks so at least). I played around a lot from removing jittering to making the bounce 0 and friction 100 and getting the seed looking good to me (it's a part of the scene but i attached the piano solely). What i thought is conversion to keyframes to edit those keys by hand which wouldn't be hard at all i guess, time consuming max. But here is the piano, take a look if you like: 11008_thedroppedpiano.rar.zip


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Brian Jones
Re: Shatter complex dynamic object after collision with floor
on Feb 1, 2017 at 10:29:50 pm

The settings with this object set seem really touchy.

11010_thedroppedpiano2.c4d.zip

-Changed the settings in Mode/Project/Dynamics/Expert to Steps per Frame = 5 and Max Iterations per Step = 10
-Changed floor Plane to a poly object from a parametric - I don't know if that makes a difference at all - and increased it's poly density a bit
-Reduced bounce of the floor plane
-changed piano parts to be Moving Mesh rather than Automatic - automatic just puts a box around all the parts (or a sphere around spheres) so if the automatic box intersects with other parts (if they are not simple enough) then when the dynamics turns on at impact they will want to explode away from the intersecting bits. *** Note here*** the piano keys are intersecting the piano so to make it more predictable you might want to change the design of the keys. ***
-Increased Angular Damping of the piano parts (that's in the Force tab)
-reduced Friction in the piano since 200 is way too much usually.

If you have one of the versions of C4D with only the MoDynamics Dynamics then it might be tougher.


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