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[BULLET] Switch constraints during a RBD simulation


Alkyum

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Hi guys,

I'm actually working on a destruction setup but I have some trouble.

 

When my Glue constraint reach an @impact value I change the @constraint_name to "Spring" to simulate some friction.

Then I want to break the Spring constraint based on the @force.
The problem is that the attribute "force" didn't appears when I change it dynamicaly during the simulation, it appears only when I directly start with a Spring constraint.

I just have the Glue attributes staying all the simulation long.

Is it normal?

Thank you in advance.

destruction_detail.hip

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Soooooo weird, I was fighting with that bug last night during 3 hours, I'm not a pro in bullet so I was thinking it was me, maybe restarting Houdini resolved the problem.

Thank you for your help Pavel ! Love your works, all my setup is based on your "Bullet Fracture Control", I'm trying to reproduce the same level of details. :)

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  • 4 months later...

Hey guys,

I am also trying to switch constraint networks based on impact data. In this file I am using a sop solver to detect when the impact happens, and then I switch from glue (which holds everything together as the object falls) to a cone/twist (so that it can bend and break). The main issues I am having right now are:

1) I am losing a buttload of energy when the switch happens. If there were a way to switch before the actual impact I'm sure that would work...

2) The cone constraints are acting funky as hell, whipping random objects all over the place!

3) I have tried many different methods but I cannot seem to get things to come to a complete rest. I have tried artificial dampening, setting objects @active to 0 when below a certain threshold (this works the best) and playing with the collision padding and penetration threshold / substeps to no real avail. 

Any help or ideas on how to switch constraint networks, or even just have the rdb fractured object stay together while falling, would be greatly appreciated! (Apologies if this file isn't notated properly but it is fairly straightforward. There are, however, 2 different networks. The glue connects all pieces but the cone lets some small pieces fly).

clusterConstraints.005.hip

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In case anyone was wondering, just setting the glue strength to 0 and not switching constraints at all seems to work just fine. It should be noted that the bias factor on the cone/twist needs to be at 0 or some weird shit starts to happen.

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