offroad

[super gnu]

seems in the new nightly build i need to set the z axis to -jammed to stop the fluid falling out of the bottom when the sim starts! (it does come back again later in the sim, the issue is a large area sim with a shallow fill.. the sudden drop in level at the start of the sim causes the whole lot to dissapear out of the bottom of the grid.

[Ivaylo Katev]

unlike the official build in the nightly build the initial fill up does not produce solid bottom automatically, it produces supporting pressure, but the liquid can step back if you push it downward.

[super gnu]

ok so i tried your tip of increasing the viscosity above one in the listener, in the official demo this possibly worked, i didnt get many comparison tests out, but with the nightlies, any values above 1 seemed to calculate really fast and have much lower viscosity.


on a related note, static surfaces correction does a good job of reducing movement in static areas, but it would be great if this could be adjustable.. id imagine using the method here it would be possible to approximately simulate much thicker stuff, as you could essentially stop any slow moving fluids from settling? as you said, its so far impossible to do really thick mud. i got a lovely effect by mapping the fluid channel with a cellular map and a gradient for cutoff.. got a lovely blobby field of mud, but of course, even with very high viscosities, it never stays still and after 25-50 frames its settled to a flat surface.

[Ivaylo Katev]

yes, the slow movement is as expected.
i have another suggestion, you can try to simulate mud using the foam. actually it has all the needed properties, use non solid source to create it.
the bad thing is that it is much slower.

[super gnu]

ok having a crack at using foam, however im a still a bit of a noob. few questions:

1. if im using a source (in brush mode on a box set to non-solid) do i leave liquids enabled in the simulator or turn them off?

2. when using a source for the foam, what controls the particle density? ive tried upping the discharge of the source but i still get the same sparse collection of particles.

3. im assuming the foam parameters in the simulator control the behaviour of the foam generated by the source? i also assume some settings will be irrelevent since im not generating the foam from a liquid.

4. from what i saw in another post about foam fluids (same discussion really) i cannot mesh these foam particles with phoenix. since splashing out on frost is highly unlikely in my scenario, can i get a reasonable mesh out of these things?

5. does the fact im using particles mean i can lower the grid density or does it still have an effect on the simulation?

6. wha governs the behaviour of particles that leave the grid? and do they get picked up by the sim again if they re-enter the grid?


i have a sneaking suspicion this is gonna be way too slow and fiddly (considering im on a 30 day trial!)

[Ivaylo Katev]

1. leave the liquid turned on, otherwise the foam will be ignored. however don't create liquid, just foam
2. the particle density is the "particles" parameter. note that the particles are produced constantly, you have to animate the parameter to go to zero after few frames
3. yes, correct. the irrelevant settings are those related to the natural birth - birth rate, threshold.
4. you can mesh them by phoenix, if you have no frost. phoenix provides a procedural texture that is white near to particle and black away from the particles. create an extra phoenix object that will mesh the particles, you can't use the original one because it is a circular reference. put it to render as mesh and select in the surface section to be based on texture. put the above mentioned particle texture in the map slot and this is all. perhaps you have to simulate one dummy frame otherwise the simulator may refuse to render, i'm not sure about this point.
5. yes, the grid density can be lowered, but you still depend on it, the particles do not interact directly with the geometry, they use the voxelized representation, if you use very low grid res, the representation may be not actual.
6. the particles that leave the grid behave exactly as inside, except the lack of bottom, they will fall below the zero level. entering the grid they are picked up again.

[super gnu]

thanks for the info.. i appreciate you taking the time to reply to a demo user.


in response however:

you mention the particles behave exactly the same outside the grid? as in, they continue on the trajectories they were following when they left the grid? and keep the same velocity? or they stop moving? or are they still considered to be in a simulation..?

im also having real issues getting a stable, dense particle cloud. if i increase the birth rate ( animated to 0 over the first frame) then the particles fly out everywhere on the second and third frames, like they are under pressure.

ive tried reducing the particle size in the simulator but it doesnt seem to help. also despite particle size now being on 0.1 cm, i have to set the particle texture to radius of 2cm to get a connected mesh.. surely i should be able to get a finer radius on the texture with such small particles?

[Ivaylo Katev]

yes, there is no fast way to fill the container with foam, like we have for liquids. i recommend to create the foam with smaller size or birth rate, and to let it to settle. you will have some initial movement, this is unavoidable