negative velocity isn't removing any fluid particles

[TKT]

I have two fluid grids set up, one to simulate water running over the edge of a wall and then one at the bottom that sims after. it made the grid way smaller and faster to calculate this way but it refuses to drain any water in the second sim so the container is constantly overflowing.

Is the negative not supported in a cascaded simulation?

The example scene for the sink has one source for outgoing velocity with a positive value, the second is negative to drain particles away. I have the same but the outgoing positive is in the first sim, the negative is in the cascaded sim. no matter the value i set, nothing is removed.

[TKT]

remade the liquid source and object, seems to be working now. i guess bugged out?

[Svetlin.Nikolov]

Hmm, do you happen to keep the older version of the scene where the issue happened, so we can have a look?

[TKT]

Hmm, do you happen to keep the older version of the scene where the issue happened, so we can have a look?

I can send the scene, it seems to be acting strange in comparison to the example scene. I'll package it into a we transfer when i get a moment today.

[TKT]

Hmm, do you happen to keep the older version of the scene where the issue happened, so we can have a look?

https://we.tl/t-fOHpJFkquV - max file is here. it was bit of a test scene so i tried to tidy it up a little, its not at origin as it was using location for an actual project.

emitter at the top and then a box to act as a drain in the second part of the sim at bottom.

at one point it just kept overflowing. then the drain started to work but drained much too quickly. now its gone back to not really draining anything as its set much higher than the output from above but still overflows by the end of the frames.

[TKT]

Hmm, do you happen to keep the older version of the scene where the issue happened, so we can have a look?

was there anything in particular to why they wouldnt get removed?

[Svetlin.Nikolov]

Sorry for the late reply! I am looking at the scene and until I find the exact issue, try deleting the LiquidDelete Source and instead from the right click Phoenix Properties of the "Drain" object please make it non-Solid and enable Clear Inside. This way it would start deleting the liquid particles that enter it and you would be able to control how quickly they get deleted by changing the size of the object.

[Svetlin.Nikolov]

Oh, there is something important that you need to do - please change the Scene Interaction rollout's mode of the WaterfallSim to "Include List" and include only the nodes that need to interact with it - I think these need to be PLainForce001, LiquidEmitter and Emitter. Please see this page for the reason why - this is very important for cascade simulations: https://docs.chaos.com/display/PHX4M...een+Simulators

You might also want to exclude the nodes that don't affect the seconds simulator too - this is not a problem currently, but could prevent errors. E.g. the plain force, the emitter source, etc.

[TKT]

Oh, there is something important that you need to do - please change the Scene Interaction rollout's mode of the WaterfallSim to "Include List" and include only the nodes that need to interact with it - I think these need to be PLainForce001, LiquidEmitter and Emitter. Please see this page for the reason why - this is very important for cascade simulations: https://docs.chaos.com/display/PHX4M...een+Simulators

You might also want to exclude the nodes that don't affect the seconds simulator too - this is not a problem currently, but could prevent errors. E.g. the plain force, the emitter source, etc.

I will try the first suggestion for changing the mesh properties to drain in a different way.

I'm a bit confused on this post though, I was reading the page you linked but not sure why the include list is a must? is it purely just so the 2nd simulator doesnt try to do anything with the water as it falls into the overlap section?

[Svetlin.Nikolov]

This is because when both simulators include one another:
1. you simulate the first sim, the second one is empty
2. then you simulate the second sim, it interacts with the first one
3. then you want to simulate the 1st sim again - however, now the 2nd sim is not empty anymore, so it might affect the simulation of the 1st sim as an obstacle or in some other way.

[Svetlin.Nikolov]

Oh, ok, mystery solved in the original scene as well:

Seems like perhaps you copied the LiquidDelete source from LiquidEmitter, and it remained with Polygon ID of 3.

Please reset it to 0 and it would work as expected, otherwise it would delete particles only on one end of the long geometry.

[TKT]

This is because when both simulators include one another:
1. you simulate the first sim, the second one is empty
2. then you simulate the second sim, it interacts with the first one
3. then you want to simulate the 1st sim again - however, now the 2nd sim is not empty anymore, so it might affect the simulation of the 1st sim as an obstacle or in some other way.

ok yeah that makes a bit more sense. will give it a go with these adjustments.

one of the other things I was wondering when it comes to adding splashes, it becomes quite difficult to not have them look a bit strange. they seem to always be perfect spheres and quite large. is this because you need to make sure sim detail is below 1cm so that the splashes can be smaller and do they ever deform or are they always spheres and rely on motion blur to look distorted?

in the examples the splashes look more natural but mine always end up looking like a mass of spheres, like marbles falling down the wall.



as for the drain problem.... yep that would do it! my bad, thats a silly thing to miss. I forgot I did that. so much frustration for such a small thing. I'll avoid copying things.

[Svetlin.Nikolov]

Oh yes, this is how the splash render mode of the particle shader looks up close. See the info here https://docs.chaos.com/display/PHX4MAX/Particle+Shader

It renders the splashes as spheres and if they are too large and unnatural, then the original problem would be that the grid resolution of the Simulator is too low and needs to be increased. The sizes of the splashes reflect the sizes of individual voxels of the grid, so large voxels means large splashes.

If you don't want to change the simulation settings, you could try fixing this at render time instead - the particle shader has a Size Multiplier that you could use to shrink the splash spheres. If they get too few and too far apart, then you could also increase the Count Multiplier option and it would create new particles between the existing ones at render time. Please try that and see if it helps, but if it doesn't look good, I'm afraid you would have to go back to the simulation first.

Cheers!

[TKT]

Oh yes, this is how the splash render mode of the particle shader looks up close. See the info here https://docs.chaos.com/display/PHX4MAX/Particle+Shader

It renders the splashes as spheres and if they are too large and unnatural, then the original problem would be that the grid resolution of the Simulator is too low and needs to be increased. The sizes of the splashes reflect the sizes of individual voxels of the grid, so large voxels means large splashes.

If you don't want to change the simulation settings, you could try fixing this at render time instead - the particle shader has a Size Multiplier that you could use to shrink the splash spheres. If they get too few and too far apart, then you could also increase the Count Multiplier option and it would create new particles between the existing ones at render time. Please try that and see if it helps, but if it doesn't look good, I'm afraid you would have to go back to the simulation first.

Cheers!

ah thank you! i didnt think to check the shader doc page, i was reading through the simulation part of splashes trying to figure out why mine didnt quite look like the examples in documentation. ok some of this makes more sense, will have a play with this.