increase tumble for falling RBD objects that use glue connstraint

[sim]

Hi all,

I have an voronoi fractured terrain and in classic fashion, there's a crack through the middle and the pieces start falling from the central crack down into an abyss.

 

To get the falling propagating outwards from the middle, I'm using a Glue network and dissolving the constraints outwards over time. My object is an RBD packed primitive 

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This all works, but the pieces tend to fall straight down as their constraints dissolve. I'd really like to get the pieces to tumble as they fall. So that just as the piece is about to fall , the exposed side closest to the abyss - starts to tilt down before the whole piece gives.

 

I'm stuck at this. I've tried simple things like increasing friction. I know one way to do this would be to model a lip on the bottom of every piece facing the centre of the terrain. But doing that by hand would be prohibitive.

 

Does anyone know how I could approach this?

 

Sim.

 

 

 

[rayman]

You can convert constraint type (for example to spring) a couple of frames before deleting constraints.

[portdusk]

You could try giving them an noisy point velocity and checking the "use point velocity" parameter.

 

Alternatively you can instance a bunch of noisey cubes directly underneath the fracture geometry and then delete them away slightly slower than you're deleting the glue network. That way the fracture object first collides with the cubes before falling away.

[sim]

Hey those are both great ideas.

 

Pavel,
I tried out your suggestion a few days ago. Thank you. Took me a while to understand how to do it, but I got there and I've definitely learnt along the way.  The results I have are promising.
Though I have to say I can't get the spring constraints to be very stable. I've played with strength, damping and mass. I can only use low values of strength, before pieces start popping to the ends of the universe on frame 2. So I use low strength, and quickly delete the spring constraint before the pieces start looking like they drooping away, and it's enough to start a tumble on most pieces.

 

Travis,

I'm not sure about the noisy point velocities - can't picture how that would give a tumble in the right direction/axis. But the random cubes placed right under pieces and deleted away just slower than the constraints. Brilliant! What a simple, but effective idea.

 

I will post back with more results.

 

Sim.

[rayman]

Yes, there are some problems with strong springs and bullet.

Another way to achieve this is to use hard constraint relationship.

Set s@constraint_type  to  "position"; This way constraints will ensure only positions and pieces are free to rotate. Set connection type of connect adjacent pieces node to adjacent points and create really small max search radius. Then you can modify each primitive so both points are on the same position (this way pieces won`t pop).