Hi,

About a month ago i stumbled on this video: http://vimeo.com/11689910 [vimeo.com]

And i thought it would be easy to create this effect in houdini (im using the apprentice version), and also a good way for me to learn about particles.

A month later and im still tearing my hair out on this one - im soon out of hair….

Used the font sop and extruded it. Looks like the 5 in the video. Made it a “static rbd object”. Placed a particle emitter, top side and inside the 5.
Used a copy sop to place random sized spheres on each particle. this works.
But all the balls just flies thru the extruded 5 number.

So i have placed a static ground floor and the spheres happily bounce of that… so somehow the rbd is working … but not on the extruded 5 number.
Tried to reversed the polygon on the 5 - though it was something with normals .. but still no luck.

Any ideas?
Anyone out there who have tried to fill and object with another object, with rbd turned on?

still pulling hairs out ..

Best regards

It's best if you post a file along with a question like this, but the first thing that comes to mind; have you toggled Static Object>Collisions>Volume>Invert Sign? That will invert your collision object so things stay inside it rather than outside.

Using the invert sign only works with the RDB solver, which is impressively slow compared to the Bullet solver. However Bullet doesnt use volumes for collision detection so the invert sign option doesn't work unfortunately.

However using the Bullet solver, check out your static RBD object in DOPS. Collisions—>Bullet Data—> UNcheck “Polygons as convex Hulls”.
This now let's you fill a hollow polygon geometry without volume based detection, and the speedyness of bullet over RBD.

Sorry for the messy file, but this was a quick squeeze in before I go to bed. Should give you an idea to play out.

Hi

Thanks both of you for the provided ideas. They gave me a few new ideas.
For future reference I will remember to post a file with my questions.

Looking at the provided file, that is a very useful way of solving the problem.

Generating points and using the rbd point object works fine, but i was more looking for a way of generating particles from a popnet, and then copying geometry on to those points and then applying rbd to those objects.

I will continue my sidefx documentation reading and see if i cant figure this one out.

best regards

Id not looked at this thread until just know, maybe it was the title ! . Cool challenge

Rob

Yes circusmonkey i agree, it is actually a fun little challenge and so after much reading im getting closer

1) I created a sphere object and a simple particle
2) then i used RBD Point Object to copy the sphere object onto the particles.
3) after this i went inside the particle and put a kill with a $LIFE==0 in the rule.
4) In the RBD Point Object -> Creation Frame i put $F. Also under Collisions i unchecked “Polygon as convex hulls”

After that it was just to play around with settings until it began to work.
Still reading, playing and adjusting.

I think it would be kind of cool if each sphere could give birth to more spheres and so on. Even when they are inside your letter shape > they could push other spheres out of the way. like a growing pile.

Rob

Nice idea Rob. Like it.

Think i will have one grownup sphere start it all, give birth to smaller ones that over time grows and starts to give birth and so on and so on. More life like.

Back to reading again, i guess

Best regards,
Bo

very cool idea