Animate RBD in 2020 (Strict Follow Input-Position)

[m-egger]

Hey,

since I didn't find anything on the matter that's less than 7 years old (And not even the mighy tokeru-cg-wiki having a post about it) I thought I'd ask for some updated insights. 

(I'm currently struggling getting a huge coal plant to fall into a sink hole. Now the ground I just did seperately as a guiding sim and now I want the coal plant to follow this ground in the fall down.)

What I'm trying to do is get the pre-ran RBD sim as collision objects or static colliders and attach the coal plant RBD pieces with constraints to those falling guide pieces. Is there any way to do that? I was just looking around the forums (here and sideFX) and I found really little about the topic.

Doing some RnD I got frustrated quite quickly because after all possible combinations of "animated" & "deforming" attributes set and collision object yes/no and constraints that I could think of for a couple of hours, the best result that came out was this:

 The test scene is attached. rbd_animate.hipnc

And that seems like I'm really not getting behind some science there. Here, I'm updating the position inside the Bullet-Solver-SOP with a POP-Wrangle to the input, but the constraints get screwed up too.

Since I'm trying to stick with the Bullet-Solver-SOP (for a couple of reasons), I'm also having a hard time getting a custom constraint SOP-solver into the mix to update the constraints seperately. I'm sure there must be a cleaner way (with the animated attribute) though. Any leads? The documentation is really sparse on this end.

Thanks,
Martin

Edited June 30, 2020 by tortoise

[Noobini]

try this see if it helps:

 

 

[m-egger]

Thanks noobini, still looking good!!! I will take a look at it first thing in the morning.

But to document/answer my own question from before: I also just found out that it is viable to set the RBD attribute "animated" to 1, however, it will only the effective when "active" is 0. Just that now again, the constraints behave quite uninterested in the animation, haha.

[Noobini]

yes the animated/deform/active combo can sometimes be finicky...tripped me up a few times...

[m-egger]

Yes indeed. But at least analyzing the pre-built Guided Simulation gave me a clue on how to do it properly for myself. I think I'll go the route of soft constraints on the guiding geometry that's now animated. Like invisible tentacles that pull the structure down. Seems the most controllable/natural after first tests.

And just to document another interesting thing with the pre-built guide feature on the Bullet SOP-Solver here: The guiding only works input geometry with primitives. I wrongly assumed it could handle it sort of like a point deform, but it just pulls the pieces apart towards the points in a weird way.