Unexpected additional impulse when simulating with Bullet

[gosch]

Hi, everybody!

I've made a small test of wall destruction using Bullet:Wall Destruction

There is a strange behavior of some of the small pieces, as the get unexpected additional impulse after collision. What is the reason and how to avoid such a strange behavior?

[Netvudu]

It is tough to help without checking the hip file...could you upload it, or at least a simpler version?

Edited July 11, 2012 by Netvudu

[gosch]

Here is the hip file!

wall_destruction.hip

[rafaelfs]

Here is the hip file!

Your drag DOP is making the sim go a bit crazier... now sure why, but it seems to be adding force.

I tested with that node bypassed and it worked as expected.

wall_destruction.hip

I also cleaned up the network a bit, you had some extra nodes that were not needed, plus it was creating SDFs for no reason since you're using bullet.

Cheers

Edited July 11, 2012 by rafaelfs

[gosch]

Thanks, Rafael! So, what is a proper way to dissipate energy when using bullet?

[rafaelfs]

Thanks, Rafael! So, what is a proper way to dissipate energy when using bullet?

I'm confused as well, drag should be your guy, but I don't know why it wasn't working in this case.

Smells like a bug to me. You should send your file to Side Effects and explain the situation.

Cheers

[rayman]

You can use vopforce DOP.

Multiply v by mass to create consistent force for each piece. You can also multiply it by FPS if you need precise control(probably not a good idea when using substeps).

To control the dissipation add another multiplication by -.1 for example. Plug this to output force and you are ready.

Now each frame velocity will dissipate by 1/10 of its mag.

Edited July 16, 2012 by rayman

[old school]

Oh I forgot about the VOP Force DOP and it's internal CVEX context set up for you with nice global input and output VOPs predefined.

With any Force type DOP you can create a Mask Field VOP which in turn can use a SOP Scalar Field or SOP Vector Field DOP or a Copy Data DOP to control where and how strong you want the Force effect to be, or both at the same time.

A Scalar Field gives you:

vector force * float scalar_mask

where the SOP Scalar Field gives you control over the global magnitude of the mask field to control the effect inside DOPs.

while a Vector Field gives you:

vector force * vector vector_mask

where the SOP Vector Field gives you control over the magnitude of the X, Y and Z field to control the effect inside DOPs.

[dark_cry]

Hi, everybody!

I've made a small test of wall destruction using Bullet:Wall Destruction

There is a strange behavior of some of the small pieces, as the get unexpected additional impulse after collision. What is the reason and how to avoid such a strange behavior?

Hi dude, i've dig in your hip and there are some constraints, i guess the constrainting workflow and glue pieces in sop level are built in shelf. Am i right? Could you kick me to the right direction how to the right workflow. I mean glueing peaces manually typing the prim numbers are hard job...

[dark_cry]

Hi dude, i've dig in your hip and there are some constraints, i guess the constrainting workflow and glue pieces in sop level are built in shelf. Am i right? Could you kick me to the right direction how to the right workflow. I mean glueing peaces manually typing the prim numbers are hard job...

i got it

[gosch]

i got it

Yea, it's houdini native Glue Cluster Tool

[gosch]

Rayman, oldschool thanks for tips!

I've made another test of creating complex constraint network (glue, spring, pin) to achieve believable building destruction:

Building Destruction