Hi,
It looks like your groundplane and drip simulation ended up in two different dop networks. I recommend moving the groundplane+merge+staticsolver set of nodes into the dripflip_sim dop network, wire it up to “merge1” AND move it above the flipsolver in the “Input Operators” list for “merge1”.
Ryan
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Technical Discussion » Drip particle fluid isn't colliding with ground plane?
- rgoldade
- 73 posts
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Technical Discussion » Source Volumes / FLIP - Collision Behaviour
- rgoldade
- 73 posts
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Hi,
I'm not sure I fully understand what you're trying to achieve. The scene file has a sphere of liquid pouring down on the liquid pig that deforms the pig and also pushes it around. What did you want to happen instead?
Thanks,
Ryan
I'm not sure I fully understand what you're trying to achieve. The scene file has a sphere of liquid pouring down on the liquid pig that deforms the pig and also pushes it around. What did you want to happen instead?
Thanks,
Ryan
Technical Discussion » Question about custom wave for flip sim
- rgoldade
- 73 posts
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Hi there,
The Ocean Source node's Falloff is set to Exponential by Frequency. In this state, it expects everything to by at y=0. Which means that the point instances you pass into Ocean Waves needs to be y=0. By setting the “ty” parameter (center-y) in “grid1” to 0, I was able to get the particles to match the preview grid.
Hope that helps,
Ryan
The Ocean Source node's Falloff is set to Exponential by Frequency. In this state, it expects everything to by at y=0. Which means that the point instances you pass into Ocean Waves needs to be y=0. By setting the “ty” parameter (center-y) in “grid1” to 0, I was able to get the particles to match the preview grid.
Hope that helps,
Ryan
Houdini Learning Materials » Question about custom wave for flip sim
- rgoldade
- 73 posts
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Hi,
This issue occurs when Ocean Source's Depth Falloff parameter is set to Exponential by Frequency and your instanced wave source points are not on the y=0 plane. Setting the y-component for center in “grid1” to 0 brings will fix this problem.
Hope that helps!
Ryan
This issue occurs when Ocean Source's Depth Falloff parameter is set to Exponential by Frequency and your instanced wave source points are not on the y=0 plane. Setting the y-component for center in “grid1” to 0 brings will fix this problem.
Hope that helps!
Ryan
Technical Discussion » Crown splash particle fluid unit example
- rgoldade
- 73 posts
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In general it's a good idea to use real-world units so everything plugs together nicely. However, the motivation for this shelf tool was to produce stable, slow-motion behaviour off the shelf. Even gravity was scaled down.
It should be pretty straight forward to modify the setup from the shelf tool to create a crown splash on the order of millimetres if real-world units are needed (NB: you likely will need substeps for stability).
Take care,
Ryan
It should be pretty straight forward to modify the setup from the shelf tool to create a crown splash on the order of millimetres if real-world units are needed (NB: you likely will need substeps for stability).
Take care,
Ryan
Technical Discussion » Drip particle fluid isn't colliding with ground plane?
- rgoldade
- 73 posts
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Hi,
Can you provide an example .hip file? I wasn't able to reproduce this issue on my end.
Thanks,
Ryan
Can you provide an example .hip file? I wasn't able to reproduce this issue on my end.
Thanks,
Ryan
Technical Discussion » surface tension attribute
- rgoldade
- 73 posts
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If you activate the “Add Viscosity Attribute” toggle in the FLIP Object are you able to see the viscosity attribute in the Geometry spreadsheet?
I would try connecting a SOP Solver to the Volume Velocity input in the FLIP Solver and creating the attribute in there.
I would try connecting a SOP Solver to the Volume Velocity input in the FLIP Solver and creating the attribute in there.
Houdini Indie and Apprentice » Disapearing FLIP fluid particles
- rgoldade
- 73 posts
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Hi,
It might be caused by your balloon collision being too thin. The FLIP solver can't properly handle collisions that are too thin. Make sure that your collisions are around two flip-sized voxels thick and that the division size of collision is at least the same size or lower. If the problem still persists, I can try and help further.
Hope that helps,
Ryan
It might be caused by your balloon collision being too thin. The FLIP solver can't properly handle collisions that are too thin. Make sure that your collisions are around two flip-sized voxels thick and that the division size of collision is at least the same size or lower. If the problem still persists, I can try and help further.
Hope that helps,
Ryan
Technical Discussion » Alternate implementation of "Gas Project Non Divergent" node
- rgoldade
- 73 posts
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Okay I see. I believe GT is meant to be the preconditioner matrix. You should be able to pass in 0 for GT's pointer and the solver will default to diagonal jacobi for the preconditioner.
Technical Discussion » surface tension attribute
- rgoldade
- 73 posts
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Hi,
Surface tension is handled as a field, so there is no particle-based attribute. It essentially computes the curvature of the fluid surface at each voxel and scales that value by the global surface tension coefficient in the FLIP solver.
It's possible to achieve variable surface tension by creating your own attribute, stamping it to a new field (using Gas Particle to Field) and scaling the surfacepressure field by this new field.
Hope this helps!
Ryan
Surface tension is handled as a field, so there is no particle-based attribute. It essentially computes the curvature of the fluid surface at each voxel and scales that value by the global surface tension coefficient in the FLIP solver.
It's possible to achieve variable surface tension by creating your own attribute, stamping it to a new field (using Gas Particle to Field) and scaling the surfacepressure field by this new field.
Hope this helps!
Ryan
Technical Discussion » Guided Ocean
- rgoldade
- 73 posts
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Houdini Learning Materials » Problems with flat tank, trying to follow tutorial
- rgoldade
- 73 posts
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Hi,
I would recommend setting the grid scale to 2 in the Ocean Source parameters window. This should fix your problem for the time being. We will fix it on our end for future builds.
I hope this helps,
Ryan
I would recommend setting the grid scale to 2 in the Ocean Source parameters window. This should fix your problem for the time being. We will fix it on our end for future builds.
I hope this helps,
Ryan
Technical Discussion » FLIP Particle Separation meaning?
- rgoldade
- 73 posts
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Hi let me try and answer a few of your questions.
I hope that helps,
Ryan
Does Particle Separation equal to Grid Spacing?The grid spacing is based on the particle separation multiplied by the grid scale. If you want to increase the resolution of the simulation, the particle separation is the most direct way.
Does Particle Separation control the number of particles?Indirectly but yes. If I have a 1x1x1 box and I decrease the particle separation, then I will need more particles to fill that box and still maintain the new interaction distance. You can also think about it as if you're filling the box with a grid and you want to have 8 particles in each voxel.. then if you decrease the grid spacing, you will need more particles to fill the box with 8 particles in each new, but smaller, voxel.
I hope that helps,
Ryan
Edited by rgoldade - May 24, 2017 11:35:51
Technical Discussion » Alternate implementation of "Gas Project Non Divergent" node
- rgoldade
- 73 posts
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What is it that you're looking to do differently at the pressure projection step? I can try and answer your questions.
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
- rgoldade
- 73 posts
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There's no real satisfying solution for upressing something like a droplet. The suction fluid tool might help direct the high res simulation to match the low res. However it tends to behave like an elastic band if the hi res deviates too much from the low res. Adding drag to match the low res velocity might also help. Both of these approaches can get the high res closer to matching the low res but it will require a lot of parameter tuning. Because of this, we only encourage upressing using container boundaries.
Houdini Indie and Apprentice » Suction Fluids, keeping Particles in Shape
- rgoldade
- 73 posts
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Hi Tom,
Can you post the hip file?
Assuming your geometry is wired into the anti-gravity properly, the particles should remain inside the geo unless the suction force is too strong and unstable or there are other forces acting on the particles.
Ryan
Can you post the hip file?
Assuming your geometry is wired into the anti-gravity properly, the particles should remain inside the geo unless the suction force is too strong and unstable or there are other forces acting on the particles.
Ryan
Houdini Indie and Apprentice » Questions about suction fluid tool
- rgoldade
- 73 posts
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It is normal for the particles to fill up the inside volume of the mesh first. Once the inside volume is full, the particles will create a layer outside the mesh depending on the “outside distance” value. It is possible to change this but it would require modifying the VEX code. What type of look are you trying to achieve?
You might find that your particles remain inside the mesh after turning the suction force off if the anti-gravity is still active. You will need to turn the suction strength and anti-gravity strength to zero for the particles inside the mesh to fall properly.
I hope this helps!
Ryan
You might find that your particles remain inside the mesh after turning the suction force off if the anti-gravity is still active. You will need to turn the suction strength and anti-gravity strength to zero for the particles inside the mesh to fall properly.
I hope this helps!
Ryan
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
- rgoldade
- 73 posts
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Could the problem be because the particles is being seeded and then advected directly afterwards
That could definitely cause a problem if your river is flowing fast enough to escape the boundary layer in each frame. The boundary layer acts as a source at the reseed step. This happens before the advection step so in your example it makes sense that using a source shows an improvement.
For slower moving rivers, the source might seed into non-empty voxels and create more particles than necessary, which will then be deleted in the next reseed step. The boundary layer doesn't over populate voxels, making it more efficient, but is susceptible to fast moving simulations.
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
- rgoldade
- 73 posts
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I've attached the .hip files used for the river re-sim. The boundary_layer_river.hip file is the “low res” river, using the boundary layer to maintain the flow rate and water level of the river. The resim_river.hip file loads in the geometry from the boundary layer example and re-sims at a higher resolution, with a collision object and only simulated in a small region of the river.
I've attached an example of using the guiding volume approach instead of the boundary layer. This is for those who are curious about the setup. Again buyer beware here. The tool was designed for use with Oceans in H16 and has the potential to be generalized for many other features. However, we have noticed some instability at the seams so we don't currently endorse using it for this purpose.
Enjoy!
Ryan
I've attached an example of using the guiding volume approach instead of the boundary layer. This is for those who are curious about the setup. Again buyer beware here. The tool was designed for use with Oceans in H16 and has the potential to be generalized for many other features. However, we have noticed some instability at the seams so we don't currently endorse using it for this purpose.
Enjoy!
Ryan
Edited by rgoldade - March 1, 2017 17:51:15
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
- rgoldade
- 73 posts
- Offline
Ah right. I should have anticipated such a question. I will post some example files this afternoon.
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