I realise that their are plenty of posts that talk about leaking glasses and disappearing flip fluids so I'm going to ask a different question.
How can I work out what resolutions I need for collision objects when working with flip fluids?
For example, I have a collision object that is 2.5 centimetres thick (working at 1 unit = 1 metre) and I need to dial the right numbers into the relevant parameters to make it watertight. Also which of the many parameters that may appear to be relevant to this is actually used? I'm looking primarily but not exclusively at these:
particle separation
particle radius scale
grid scale
collision separation
division size
I know plenty of folk will just say make your collision object thicker but that's not possible in some situations which is where I'm starting out from.
thanks,
A>
Tips for working out the right resolutions for colliders
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- Andi Farhall
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- Enivob
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The way I do it is to visualize the actual collision geometry. I take two approaches depending upon the simulation type. For instance if it is just RBD objects then I use the visualizer on the Static or RBD Objects nodes to dial in the resolution.
If the simulation is FLIP based I generally manually create a VDB representation of the collision object and place the Static or RBD Object nodes into Volume Sample mode and reference the VDB representation directly from my SOP network.
For FLIP based simulations you want to make sure you double check your collision geometry using the flipobject visualization options. By default your flip particle separation is the collision resolution. If you need more resolution for your collision geometry you can “decouple” particle separation from collision resolution and set each value separately.
Overall, I just raise the default value of 30 to 96 to start off with.
If the simulation is FLIP based I generally manually create a VDB representation of the collision object and place the Static or RBD Object nodes into Volume Sample mode and reference the VDB representation directly from my SOP network.
For FLIP based simulations you want to make sure you double check your collision geometry using the flipobject visualization options. By default your flip particle separation is the collision resolution. If you need more resolution for your collision geometry you can “decouple” particle separation from collision resolution and set each value separately.
Overall, I just raise the default value of 30 to 96 to start off with.
Edited by Enivob - March 22, 2017 11:54:43
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- Andi Farhall
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- Enivob
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Your sim is leaking out of the collision object because the collision object lacks enough resolution to contain the fluid. Use the flipobject collision visualizer to inspect the final resolution of the collision surface that the flip fluid will encounter. (shown in purple below)
Edited by Enivob - March 25, 2017 23:03:49
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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- Enivob
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By default fluid and collision resolution are linked. You can decouple them and offer more resolution to collisions. Ideally this will produce a collision object with fewer holes. But it is still going to leak a bit at the top.
Edited by Enivob - March 25, 2017 22:59:07
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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- Enivob
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What is typically done is to create a copy of the render mesh and edit it so it presents itself as a thicker collision object. This collision proxy object will not be rendered so feel free to expand the outer edges. Try to keep the inner edges as close to original position as possible.
Having a thicker collision object will also allow you to use a lower collision resolution for faster simulation times. So try both techniques. Thicken up the collision mesh and lower the collision resolution a bit.
Having a thicker collision object will also allow you to use a lower collision resolution for faster simulation times. So try both techniques. Thicken up the collision mesh and lower the collision resolution a bit.
Edited by Enivob - March 25, 2017 23:03:27
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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- Andi Farhall
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Thanks enivob, so many places to set so many values. I've tweaked the collision separation value right down and watched the SIM through and it seems watertight now. Having read about reseeding I realise that particle count isn't an accurate reflection of the amount of fluid. I assume the size at which I working at is also a little problematic given that it's only 2 units. I know people recommend keeping the scale at 1 unit 1 metre but this might be an exception to that rule.
Cheers,
A
Cheers,
A
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- afaria
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Hi
I'm facing similar problems with flip leaks.
I usually follow Enivob advice and edit the outsides of my geo to be thicker. but in this case, It can't be super thick, because then the huge gaps show up in the render as it's a close up shot
What I'm trying to achieve is: I have a bowl of soup and there's a ladle that scoops up the liquid.
I've been tweaking the collision separation , decreasing particle separation. but there's no way the liquid stays in the ladle after it gets scooped.
Even when i increased the laddle tickness by a lot it didn't work
any advice?
Editing post to add the files if it helps
I'm facing similar problems with flip leaks.
I usually follow Enivob advice and edit the outsides of my geo to be thicker. but in this case, It can't be super thick, because then the huge gaps show up in the render as it's a close up shot
What I'm trying to achieve is: I have a bowl of soup and there's a ladle that scoops up the liquid.
I've been tweaking the collision separation , decreasing particle separation. but there's no way the liquid stays in the ladle after it gets scooped.
Even when i increased the laddle tickness by a lot it didn't work
any advice?
Editing post to add the files if it helps
Edited by afaria - Jan. 30, 2019 13:02:06
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