View Full Version : Object pieces jumping with collision

05-30-2007, 02:06 PM
I have a couple of objects that I'm using collision to do the dynamics. The collision is set on a cone with the hard object as a ring. The idea is to get the ring to break up into pieces, which it does. The problem that I'm having is that the pieces want to jump a little bit after the impact. Is there a setting that I missed to prevent this?

05-30-2007, 02:30 PM
The short answer is "probably". That is unfortunately one of the problems with LW dynamics-- You read the manual, set it up according to the examples, and it almost works.... You can never be quite sure if the reason is user error or a bug in the software.

You may want to add a null with gravity, if you haven't yet, to help hold the objects in place after the dynamics are spent.

If you want to post your scene or at least some screen shots, maybe we can help more.

05-31-2007, 08:32 AM
You probably want to set your HardFX>Collision>break distance to something other than 0. It's this which determines when sub parts are going to affect each other after something has broken the hardfx object. If it's zero, they try to affect each other immediately after impact, which often means they're overlapping, and thus they 'push' each other away, hence the jump you get. A non zero break distance stops this effect.

05-31-2007, 03:35 PM
Dodgy's idea got me started down the right path. When I changed the HardFX>Collision>Collision by to a sphere is stopped the jumping. I think that gave more space between the hard object and the collision object so it didn't mess up the calculations.

05-31-2007, 03:47 PM
My problem is the Hard FX object is inexplicably jumping BEFORE the collision occurs, even though I've checked the option to have it all start at the collision. Grrrrr

05-31-2007, 03:56 PM
Wanna send me a scene file?

06-02-2007, 08:52 PM
You are too kind! I would love to have you look this over for me, once I get back to it. Another project with a shorter deadline has pushed this one aside for now, but I have no doubt I'll still need help with it when I resume. I'll PM you when I have the files zipped together... thanks in advance!

06-03-2007, 05:38 PM
Update: I stopped the ball from jumping by removing all FX from the ground plane. Sadly, now that is isn't a collision object, I won't be able to use gravity on the ball, but at least I've got it rolling, which is what the scene calls for. Strange that just turning off the FX on the ground plane didn't stop the jumping, I had to remove it completely.