I need help with a dynamics challenge. Simple concept... can it be done?

[supernovavfx]

I have a complicated visual i want to create that requires me to figure out one ( I thought ) relatively simple dynamics set up.

Here is the set up I tried and hope to find out how to pull off:

I have a simple only 5 elements. 3 chain links and 2 static rings. All 3 links are interwoven with each other like a real chain.

The left and right links are "linked" to the static rings. the MIDDLE link is where the issue is. I am going to have some other elements come falling down onto the chains ( so i guess there will be more than 5 elements, but those dont matter as to this question )

The middle link will be made up of some pieces.... what I want to happen is that when my falling elements hit the chain, the center chain breaks apart ( into its pre cut pieces ) as the falling objects hit the chain.

I've set this up, and with 3 links its simple and easy... set them to dynamic and they fall with gravity and hang their connected to the static rings. BUT... the pieces that make up the link that I want to shatter on impact... begin shattering almost immediately because they 'technically' hit the other links... I dont want this... I want it to hold its shape hanging in there with the other links for the 1 - 2 seconds it takes for my falling objects to hit them. I can't think of a way around this. I want the pieces of the middle link to not shatter when touching the other links.

I put a "dummy" link in the middle links place and parented the pieces to it... so the pieces fall and "hang" with the others, but now I need the middle pieces to react to the falling objects. Im not sure this even can be done. if anyone knows how to pull this off or even IT CANT would be helpful and ill have to re concept the segment....

[S. Houtzager]

It sounds like you know this but not sure.  Do you know about the "activate on hit" check box?  An object can just be floating until it is struck by another object. If the 3 links are just hanging there it might work. Pg 867 in the manual.

[supernovavfx]

yes I do, thank you Steven... the problem is that when the simulation becomes active... gravity takes over and the other links 'touch' ever so slightly the pre cut up link... and it begins breaking apart RIGHT AWAY...  not obviously what I want.  There may be a complex compositing way to do it... but  I have concepted a way around this that I think will look cool... but its a pretty interesting dilemma... I would think there would need to be some kind of parent child ability but I'm not sure.

[AVTPro]

Hi Scott.

I haven't gotten into EIAS Dynamics so this sounds very impressive. I generally use Maya so I was hoping some insight can be transpose across to EIAS. For shattering a breaking stuff I use DMM which comes with a "no break" area. Is there a way that you can set up a "no break" object and scale it back at the time collision object hits? Or is there away to split the animation in to part, the first with not breaking objects and the second where the initiation state of the simulation is just before impact? Lastly, maybe some roughness setting that can be stiff during the first part of the sim, and make the material more breakable at the point of impact?

[supernovavfx]

great to hear from you... I hope your doing well!   Your far more advanced with linkings and intricate motion than I am, but your questions are ones I have thought about.     If Bullet allows for keyframed control 

and more nuance... I have not found it in the manual.  Maybe it exists somewhere but thats why I am asking.   I "KNOW" exactly how to do what I want but the bullet system does not allow for it from what I can tell and that is this.    #1  I make the chain with complete links.... set up the dynamics and let it go... the chain would naturally sag a bit in the middle... perfect.    I would pick which link I wanted to be the weak one and take the

"pre cut up" chain 'link' and make it a child of the non pre cut up link.  I would align it exactly to begin with.    So the sim would run.... the chain would sag but NOT break because its using the dynamics from 

a solid link....  when the object falls on the chain ( and shatters the link ) I would like to be able to take the pieces of the "pre cut up link" and in have the bullet dialog box which already HAS an "ACTIVATE ON HIT" 

check box... to have a SECOND activate on hit check box with a pull down.... where you could pick the layer or object that you are telling the simulation to 'have permission' to dynamically interact with those pieces.

This would technically still call for 2 renders I think.... one would be every frame right up to the very frame that the secondary object touches the first pre cut link piece....  so then the chain would sag a bit naturally

with dynamics... and the pieces would lie dormant... only to respond to a second "level" of interaction.   This is something I can not find or see Bullets interface allowing for.   Im NOT complaining.  Work arounds are part of an animators daily job...    and since this is a personal piece for my new reel... I am adjusting my concept a little to allow for the current Bullet dynamics to work as I know how to use it.    Animating roughness and stiffness is very smart... thank you.... but I do not see that capability... reading the docs I think there are a few animate able settings.... but I'm still in my infancy messing with this.... very fun and cool stuff I plan on using a LOT going forward....  especially now that the speeds of trial and error have gotten to where I can kick out work daily.    Some of my first dynamics laden animation \ motion graphics are finished and ill share them when I'm done in the weeks to come....   :)