RBD concave thin wall collisions not detected

[neurostudio]

hey guys i am having a little bit of an issue with this test.

 

i picked up this setup from another thread on this forum however in this particular scenario it doesn't seem to work as i am probably missing something.

basically the pieces getting activated and falling, do not collide with the inner shrunk body volume i created and - since i am a houdini newbie - i am struggling to figure this out

 

tried to change geometry representation to concave, tried to increase resolution of colliders, but nothing worked so far.

 

i'd be really grateful if anyone could suggest a possible solution.

 

here's HIP and assets in case you want to have a look.

https://www.dropbox.com/s/eush4f5hus2uhwy/fracturing%20animated.zip?dl=0

 

thank you in advance.

[bunker]

You should use convex pieces with Bullet, the convex decomposition SOP can help with that.
convex pieces are slow and (very) buggy.

[neurostudio]

7 hours ago, bunker said:

You should use convex pieces with Bullet, the convex decomposition SOP can help with that.
convex pieces are slow and (very) buggy.

Hey Julien,

I am gonna give that a shot and report back. thank you

 

Edited January 5, 2020 by neurostudio

[neurostudio]

10 hours ago, bunker said:

You should use convex pieces with Bullet, the convex decomposition SOP can help with that.
convex pieces are slow and (very) buggy.

Hey Julien, 

I have been implementing convex decomposition (probably the wrong way), and made a bit of a progress. 

Would you mind having a look at my file? Assets .abc is included.

https://www.dropbox.com/s/eaheclpww2w090l/FRACTURE.zip?dl=0

thank you

 

[bunker]

I had a look at your HIP file, there was a few issues.
- the left side of the body didn't have a name attribute, same of the new faces from the PolyExtrude
- convex decomposition won't be consistent on animated geometry

a much better way is to create all your pieces on frame 1 and pointdeform them to transfer the animation.
for the activation, you can use a wrangle in DOPs and lookup your pointcloud directly.

girl_fracture_05_convex_decomposition2.hiplc

hope that makes sense.
 

[neurostudio]

3 hours ago, bunker said:

I had a look at your HIP file, there was a few issues.
- the left side of the body didn't have a name attribute, same of the new faces from the PolyExtrude
- convex decomposition won't be consistent on animated geometry

a much better way is to create all your pieces on frame 1 and pointdeform them to transfer the animation.
for the activation, you can use a wrangle in DOPs and lookup your pointcloud directly.

girl_fracture_05_convex_decomposition2.hiplc

hope that makes sense.
 

Thank you so much  Gonna dive in now and see if I learn something. Will let you know!

[neurostudio]

1 hour ago, neurostudio said:

Thank you so much  Gonna dive in now and see if I learn something. Will let you know!

i had a look at your setup and certain things definitely make sense, even for a newbie like me! thank you!

however, collisions are still not working and the pieces fall straight through the collision volume. trying to figure it out!

 

 

[bunker]

not sure what the dark blue object is but it should also be a convex packed primitive object.

[neurostudio]

Just now, bunker said:

not sure what the dark blue object is but it should also be a convex packed primitive object.

it's just the collision representation of the inner volume

got it. i'll try to do that now!

[neurostudio]

1 hour ago, bunker said:

not sure what the dark blue object is but it should also be a convex packed primitive object.

julien, i think i am getting there

now  i need to exclude the collider (which is now a packed object) from the activation pop wrangle, but i really can't think of how.

 

 

 

girl_fracture_07_convex_decomposition.hiplc

Edited January 6, 2020 by neurostudio

[bunker]

you can use the name attribute to filter out objects to activate in the pop wrangle:
eg: if your collider is named "collider"

if(s@name!="collider"){
// activate the other pieces

}

Edited January 6, 2020 by bunker

[neurostudio]

2 hours ago, bunker said:

you can use the name attribute to filter out objects to activate in the pop wrangle:
eg: if your collider is named "collider"

if(s@name!="collider"){
// activate the other pieces

}

thanks julien!

now the collider is excluded, however the pieces collisions are not working properly. 

trying to figure this out

alession odforce_01.hiplc

[woodenduck]

The blue collision object you are visualising... is that created using a static object dop? If so, are you visualising the "Collisions/RBD solver/Volume" tab rather than "Collisions/Bullet Data" tab??? I think you may not be seeing what the solver is seeing. 

[bunker]

of cource, you're using volume collision (blue) that's not going to work. Bullet uses Packed primitives only.

[neurostudio]

22 minutes ago, bunker said:

of cource, you're using volume collision (blue) that's not going to work. Bullet uses Packed primitives only.

i am using packed prims now, but still not working correctly.

still trying to figure it out.

[bunker]

you should watch this, it's still relevant: https://www.sidefx.com/tutorials/h13-masterclass-bullet/

[neurostudio]

22 minutes ago, bunker said:

you should watch this, it's still relevant: https://www.sidefx.com/tutorials/h13-masterclass-bullet/

thanks! will do now.

[neurostudio]

10 hours ago, bunker said:

you should watch this, it's still relevant: https://www.sidefx.com/tutorials/h13-masterclass-bullet/

hey julien,

i kinda solved it... i got a little confused along the way, but tidied up things in the end

ended up getting rid of convex decompositions for both collider and rbd object.
used concave representation for both and reduced collision padding and split impulse threshold by a lot.
of course now it's super slow and the result isn't super stable, however it will work for what i need.

 

thanks guys for the help !
 

[woodenduck]

Glad you got it working, and of course whatever gets the job done is great. However, I would encourage you to investigate using convex hulls for all collisions. You will see vast improvements in speed and stability. They can be a little trickier to set up, but the rewards more than worth it. 

[neurostudio]

7 minutes ago, woodenduck said:

Glad you got it working, and of course whatever gets the job done is great. However, I would encourage you to investigate using convex hulls for all collisions. You will see vast improvements in speed and stability. They can be a little trickier to set up, but the rewards more than worth it. 

will do cause honestly the sim is a little jittery and not all collisions are perfect 

maybe i'll try this method next time.

thanks!