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Prevent "self collisions" before object hits the ground?

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Ryan ConstantinoPrevent "self collisions" before object hits the ground?
by on Feb 10, 2016 at 9:52:36 am
Last Edited By Ryan Constantino on Feb 10, 2016 at 9:53:06 am

I have an object that is made up of a bunch of cubes. Imagine a complex tetris piece. I want it to fall to the ground and crash into a bunch of separate pieces. When I use the rigid body tag, and change the attribute for "individual elements" to "All" it just explodes in place without falling (presumably because some of the cubes are slightly intersecting with each other. The cubes are 100 cm, and I moved them in increments of 100). How do I prevent the pieces from "self colliding" before the whole thing hits the ground?


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Brian JonesRe: Prevent "self collisions" before object hits the ground?
by on Feb 10, 2016 at 3:59:19 pm

you can turn off Self Collision and use expresso to detect collision and then turn on self collision. If you don't control the self-intersection it will still 'explode' when self collision is turned on though. Here's an example with a Thrausi'd cube (Thrausi is not needed it just did the cuts) where there is no intersection but the closeness of the objects does make them start to separate during the fall if self collision is not turned off.

9769_xpressotokeepthrausitogetheruntilimpact.c4d.zip


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Ryan ConstantinoRe: Prevent "self collisions" before object hits the ground?
by on Feb 10, 2016 at 9:14:05 pm

Thank you for the zip file, it works perfectly....I think. Is this particular expression linked to the "thrausi fracture object"? because when I have another fracture object in my scene it doesn't work. But if I "ungroup" and delete the other fracture object it seems to work perfect.

Also, do you know if there is a tutorial out there some where to learn a little bit more about this xpresso command? Thank you for your help!


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Ryan ConstantinoRe: Prevent "self collisions" before object hits the ground?
by on Feb 13, 2016 at 4:38:26 am

Is there a way to program the xpresso to activate the self collisions only if it hits the ground? When the lower most cubes hits the floor it activates self collisions for all of the cubes and the cubes that are still up in the air begin to separate. I want them to separate only when they hit the ground. Is this possible?


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Cassius MarquesRe: Prevent "self collisions" before object hits the ground?
by on Feb 10, 2016 at 4:17:49 pm

can't you scale them down a bit to the point they don't explode, do and cache the simulation then increase them back up?

that and manually turning on colisions when the first piece hits the ground may do the trick.

Cassius Marques
http://www.zapfilmes.com


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Ryan ConstantinoRe: Prevent "self collisions" before object hits the ground?
by on Feb 10, 2016 at 8:23:20 pm

Is there a way to scale all of them down at the same time relative to their individual anchor points? There's nearly 1000 blocks. Scaling them down one by one would be very time consuming.


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