Animated colliding objects

[freejonah]

I have a project coming up that will require me to hand animate objects but get them to collide with one another. I'm an experienced Houdini user but setting up DOP simulations has never been my strength. 

I've attached a hip file with the basic situation here: moving_furniture.hip

Furniture will be sliding around, probably animated by hand. The objects need to bump into one another and react naturally while doing their best to follow the target animation. I had assumed that this would be some sort of combination of RBD objects, proxy Geo & pin constraints, but I've been unable to understand how to wire it up. There are so many great examples using this sort of thing but nothing that really explains how to combine following constraints that are animated in world space. 

Thanks so much 

[Midasssilver]

Well, you can certainly sim one object, then convert that cache to a collision object in another sim, so you can mix animated and rbd objects that way. You can also crumble apart an animated object as well, by preserving @animated on the objects you want. Unfortunately what you are describing doesn't seem easy. With a RBD fracture, you are able to distinguish between which pieces are animated and which are simulated over time, but as far as somehow having an object both retain animation, but also dynamically simmed, and seamlessly bridge the gap between the two doesn't seem like an easy feet.

 

I have seen people mention getting mutual feedback between RBD objects, so maybe something like that could be accomplished. My only question for you is why do you need to hand animate the furniture in the first place? Can't you just give it an initial velocity and rotate it in the right direction, to accomplish the same thing?

[freejonah]

Sorry I guess I wasn't clear what I'm talking about. I wanted to just have 3 rbd objects bumping into one another. My thinking was that I could animate the objects and then have pin constraints created based on that animation. Each of the 3 objects would then be attached to their relative constraints. The DOP network would have an RBD object for each piece of furniture that is doing it's best to follow the motion. does that make sense?

Edited April 4, 2019 by freejonah

[Midasssilver]

That doesn't make much sense. The 3 rbd objects bumping into one another is fine. But you said you wanted to animate the objects and have pin constraints based on that animation? Normally you would pin points of an object, not an entire object. You can bring your objects into DOPs with their animation, but then they won't be active objects,  they will be static deforming objects. What I'm trying to say is, it is not easy to blend animation and dynamics. I know it can be done, but not very easily. And, I'm pretty certain that the way that would be accomplished wouldn't be with constraints.

[freejonah]

Hi guys. Thanks for the sidebar help and private messages. I realize now that it was a lot simpler than I was making it  as usual. I found that using more than 4 constraints on a piece of furniture was overkill so I created a string that allows you to easily pick which ones you want to engage the sim while bypassing the ones you don't.

Attached is the demo file we discussed. It's simple but I'm pretty sure some of you guys will know of a cleaner way to do it. If you have something to share that would make this work better I'd be happy to take a look. 

Hip file here bumping.18.hip

 

 

[Midasssilver]

Pretty cool. I didn't know u could do that  I'm going to check it out and hopefully learn some stuff