View Full Version : Fun Bullet problem: trying to have a suspended object crumble away

09-26-2015, 01:54 PM
The effect I want is for an object that's suspended in the air and that's been Fractured to begin falling apart and the pieces drop out of sight.

Using a changing gradient to control the clue strength of the parts object is easy, it's getting the pieces to drop how I want. Unless the parts object starts out sitting on a collision object it just falls away, but that collision object then blocks the bits from dropping through it.

I did experiment with XSwampyX's tutorial on doing something similar using DP part move and procedurals (instead of Bullet) but I wasn't able to get the blasted-apart bits to then move in a straight line downward, only the entire object layer.

It's a conundrum. Anyone have an idea?

Many thanks in advance!

09-26-2015, 02:20 PM
This is definitely doable. Isn't there an option to make your collision object an event trigger and not an actual colliding object.

09-26-2015, 02:29 PM
Have you tried negative glue strength? I just tried it and it works fine.

And I wouldn't have thought you would need to use a gradient. I'd just use an envelope curve to take the glue from positive to negative.

09-26-2015, 03:19 PM
The negative glue lets them pass through, thanks. The reason for the gradient is I don't want the object to collapse all at once. A null-driven gradient lets me start the crumbling from the bottom and travel up the object.

09-26-2015, 03:57 PM
Intriguing! Can you post the render on Vimeo?

09-26-2015, 04:57 PM
I second that. Or can you post a scene?

09-26-2015, 09:08 PM
Okay, here's a sample scene file that's getting close to what I'm after. Still needs tweaking but it's illustrative.

I never got the junk to fall through the floor object satisfactorily even with negative glue strengths, but I was able to finesse the issue by having the "floor" retract at the proper time so the bits could fall through. The effect would be better with smaller chunks but this was a good mix to get the idea rolling without too much computation time.

One thing I still haven't gotten working how I like is fracturing an object like this one with a hole through it. Fracture fills the hole with junk, and if I fracture first and boolean out the tunnel I get annoying point merge issues so the area around the tunnel becomes one big block and has to be broken up again. I expect one answer would be to boolean the tunnel out, then quarter the object and fracture each quarter separately? This version has a lot of ugly chunky stuff in the tunnel where I manually deleted the crud fracture fills the hole with. I didn't want to spend a lot of time on that aspect, I'm more interested in the crumbling behavior right now.

Hopefully this clarifies what I meant by using the gradient to cause a progressive collapse instead of the object collapsing all at once. I have a render done, I'll post it up in a few.


09-26-2015, 09:31 PM
So here's a quickie render of the sequence as it's set up in that scene I uploaded.


09-27-2015, 12:35 AM
Nifty. Thanks.