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Houdini 18 rbd material fracture woes - can't keep static


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Hi guys it's been a while since I was on here due to work but I'm digging into Houdini again.

I have a simple scene.. a ball.. I scattered some points on it..  then used those points in the new rbd material fracture tool.  It seems to work..  the points fracture the ball.. giving me smaller pieces in the impact area.. and the rest is bigger chunks.

 

However I can't for life of me get those bigger pieces to remain static!  Is there any sensible way to do this? So far all the pieces fly away.

 

Ideally I want to use this tool because I like the interior detail and edge random features it has.

 

Can anyone help here ? It's probably really simple but I have been trying all day. I'm not great with wrangles either :/

Ta

Anthony 

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34 minutes ago, Noobini said:

works...but how would i know if it works for your scenario ? I simply don't.

 

 

Crumbles.gif

So what did you do exactly ? Are you using a wrangle to pin the other pieces or is there a setting in the rbd material node ?  

I tried a wrangle but for some reason I can't seem to select the packed points I need it's like the node unpacks them or something

The scene is pretty much as simple as you have except i have an object colliding.  I can't share the geo for this scene I'mafraid

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24 minutes ago, anthonymcgrath said:

So what did you do exactly ? Are you using a wrangle to pin the other pieces or is there a setting in the rbd material node ?  

I tried a wrangle but for some reason I can't seem to select the packed points I need it's like the node unpacks them or something

The scene is pretty much as simple as you have except i have an object colliding.  I can't share the geo for this scene I'mafraid

me wrangling ?...pffft couldn't wrangle meself out of a wet paperbag...just pin by bbox...that's the easiest cop out...other ways are groups...slightly more finicky.

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simple_ball_Fracture.hiplc

built a simple scene of a ball being hit by another - i stuck a sticky inside the network... basically i need:

1
the ball to not start falling the second the sim starts - i need it static.

2
only the pieces that were created from my red scattered points to be active - the rest i need static.


I cannot for the life of me understand why this is so convoluted to sort out with that rbd material fracture node - any ideas on approaches to this would be a huge help its really biting me in the neck :(

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2nd obvious point...you haven't used rbdconfigure...should start doing serious RnD on this node...coz it's where you define active/pin/sleep blah blah....you know...all things essential to a sim :blink:

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here's the 1st attemp, it is using the most basic ideas, bbox.

- rbdconfigure:

   tab1 everyone is inactive

   tab2 only the ones in the bbox is active

this is very unsophisticated, as I'm not sure your exact meaning of point 2

The bbox approach is crude...if you look at my Idiotic Jones gifs...the selection cannot be done with bbox but with 'size'...so the smalls have less glue strength while the bigs are stronger.

 

vu_simple_ball_Fracture01.hiplc

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i have a ground plane that i wil add in later but the object is suspended above the floor... i dont need it to fall on the floor and rest... i just need it floating there.. suspended.... then when hit only the pieces fall and hit my ground plane.



not used the rbdconfigure no - can you please help me out here i have no idea how to use that sodding node and all i can find is f**king entagma tuts and varomix with "heres a box i dropped the material fracture node on" - i cant find any vid for using that node especially where it involves using my own custom points

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2 minutes ago, Noobini said:

here's the 1st attemp, it is using the most basic ideas, bbox.

- rbdconfigure:

   tab1 everyone is inactive

   tab2 only the ones in the bbox is active

this is very unsophisticated, as I'm not sure your exact meaning of point 2

The bbox approach is crude...if you look at my Idiotic Jones gifs...the selection cannot be done with bbox but with 'size'...so the smalls have less glue strength while the bigs are stronger.

 

vu_simple_ball_Fracture01.hiplc

cool thanks i'm taking a look now

 

the bbox is crude but might work for what i need

 

point 2 is already fixed in that method you've given me - only the pieces in the bbox are activated - the rest stay static

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2 minutes ago, anthonymcgrath said:

i have a ground plane that i wil add in later but the object is suspended above the floor... i dont need it to fall on the floor and rest... i just need it floating there.. suspended.... then when hit only the pieces fall and hit my ground plane.



not used the rbdconfigure no - can you please help me out here i have no idea how to use that sodding node and all i can find is f**king entagma tuts and varomix with "heres a box i dropped the material fracture node on" - i cant find any vid for using that node especially where it involves using my own custom points

right now, you can set the ground to none in my scene and it will do as you wish...no ground needed.

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9 minutes ago, Noobini said:

here's the 1st attemp, it is using the most basic ideas, bbox.

- rbdconfigure:

   tab1 everyone is inactive

   tab2 only the ones in the bbox is active

this is very unsophisticated, as I'm not sure your exact meaning of point 2

The bbox approach is crude...if you look at my Idiotic Jones gifs...the selection cannot be done with bbox but with 'size'...so the smalls have less glue strength while the bigs are stronger.

 

vu_simple_ball_Fracture01.hiplc

this bounding box method seems to work really well thankyou so much for helping out - i've also found i can take my oriignal points i scattered onto my shape to fracture ...and then copy a sphere... then use those spheres to create my bounding geometry which is equally cool :)

thanks again!

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here's the next level...where if a simple bbox just won't do

the selection here is based on groups

Here's a GOTCHA, say you have mygroup, and in rbdconfigure you want !mygroup.....won't work !!! It need explicit group name. And hence you see in my scene I have largechunks...then I also must have smallchunks (handle it before rbdconfigure). You can't conveniently

say !largechunks in rbdconfigure. (who knows, they could improve on this in future..but for now...you can't use !group)

So now in this scene, the largechunks are inactive, while the smallchunks sleep...until hit by an asteroid.

 

vu_simple_ball_Fracture02.hiplc

Edited by Noobini
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try changing area selection in groupexpression from 0.1 to 0.9 and see the diff. Enjoy foolin' around....it's the only way to learn.

(the next level up is rbdconstraint properties and the likes...which is what I'm doing for the crumbling torus)

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awesome - i haven't took a look at your v02 scene yet but i definitely will - this rbd configure is exactly what i was missing and wondered where it all went to hehehe!  It makes alot more sense now overall.  I'll try the group expression tweaks too!

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22 minutes ago, Noobini said:

here's the next level...where if a simple bbox just won't do

the selection here is based on groups

Here's a GOTCHA, say you have mygroup, and in rbdconfigure you want !mygroup.....won't work !!! It need explicit group name. And hence you see in my scene I have largechunks...then I also must have smallchunks (handle it before rbdconfigure). You can't conveniently

say !largechunks in rbdconfigure. (who knows, they could improve on this in future..but for now...you can't use !group)

So now in this scene, the largechunks are inactive, while the smallchunks sleep...until hit by an asteroid.

 

vu_simple_ball_Fracture02.hiplc

well heeeeeeeeeeeeeeeeeeey, looks like they've improved it.....SNORRRRRT

I just tried !largechunks in tab 2 just for the hell of it...and it worked !!!! FMD.

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