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Collision Issues with static object

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hopeschroers
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Hi guys,

I'm pretty new to Houdini but I've been working alot with particle fluids. I'm trying to create a water sim that has a sphere dropping into a container of fluid. I have followed the tutorial for floating ball in the flip (that's the idea I'm going for, I know how to make a ball float) but my container is oval and the flip tank bounding box is not round.

I decided to just fill a container with fluid by using a flip fluid object. I made the container a static object and the flip fluid interacted fine. Then I added my sphere (made it a polygon instead of a primitive) and made that an RBD object, when I run the animation, it doesn't hit the water it bounces on this invisble surface.

I turned on my guides to be what's up. The container has the collision padding covering the top where my geometery has a cut out for the sphere to fall into.
I've tried a bunch of things to play around with the static object settings and I cant it to work. I have pictures attached and the file (mind the naming)

How do I fix this so I can have the sphere hit the water so it can float.
Image Not Found

Attachments:
Collision Guide.JPG (170.3 KB)
collisionguide2.JPG (325.0 KB)
shaded.JPG (172.4 KB)
vellumProject - CopyV2.hipnc (3.1 MB)

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BradASchreiber
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Change your Solver type to RBD in DOPs. Still attached.
Edited by BradASchreiber - Dec. 13, 2018 12:42:15

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Image 1.png (361.9 KB)

Brad Schreiber
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hopeschroers
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Thank you! I also found another solution recently where I continued using the bullet data and in Static Object for the fountain> Collisions>Bullet Data>Geometry Representation>Concave
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HammerHeadCat
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I'm new to Houdini.

I'm trying a very simple task of dropping a sphere into a box. I can't figure out why it's not working.

Please have a look at my file if you have time. I've changed the setting to RBD and yes, the sphere falls into the box but then it falls through the bottom of the box. Very strange.

Attachments:
FlipFluid2.hiplc (1.6 MB)

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hopeschroers
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@HammerHeadCat

Make sure your box has thickness. If the bottom of the box is only a flat plane (meaning its infinitely thin) then the solver will not recognize and the sphere will fall through. Extrude the shape to add thickness. If you want a thin surface you can always use “proxy geo” which is creating an object that DOPs can see and produces the interaction you desire, then the geo that is rendered is the thin surface that you want.
Common example to use that trick for is flip fluid in a wine glass.
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michaelh99
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At the risk of resurrecting what some might consider an old post, I'm replying here because the difficulty I'm having is very similar.

Doing a beginner RBD sim with a simple fractured box and box below that with a hole completely through. My goal at the moment is to have half the pieces fall through the hole and the other half settle on the "ground" box. I'm really just working through the process so, baby steps.

It all mostly works except that the pieces settle on the top of the ground box and don't fall through the hole.

Changing the simulation to RBD from Bullet, as recommended above, results in the pieces never breaking, even with glue strength at 1, and the fractured box just sitting there, whole.

I started with this tutorial https://www.sidefx.com/tutorials/houdini-ground-fracture-rbd-tutorial/ [www.sidefx.com]

If you can recommend a different tutorial I'd prefer that, so that I can work through the steps from scratch, though if there's a simple answer, that would be great too.

TIA!

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Fractures.jpg (208.3 KB)

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michaelh99
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Found the answer before my post was approved. Here's a link for the future...

https://www.reddit.com/r/Houdini/comments/kuk0ve/rbdbullet_with_holes/ [www.reddit.com]
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