Play speed parameter problems

[larex39]

Hi Ivaylo I have different problem. Is there some setup for cashing particles ,which can help for better time stretching. I tryed value 20 for storage quality, also exporting all chanels including velocity but i have not usefull results. Basicly I want to simulate liquid pouring into glass with normal speed and after this simulation i want to do slow motion from it (4x slower - play speed value 0,25). If im using linear blend method the initial stream are gradually reveal and dissipate but it look realy not natural. It is not like slow motion but like opacity fade blending between two frames. (you can try it you will see). So i thought that velocity blend will help but the resuls are even more useless. It looks like every third frame are going backwards. Only thing what it seems to work is foam, which is nicely blended and it looks naturaly. And I dont want to simulate it with slower initial speed because the simulation is not 100 percent same like in normal speed. Do you have some idea about this problem? Realy thank a lot

[Ivaylo Katev]

the storage quality does not affect the playback time scale.
the slow playback is not reliable, it's better to simulate directly in the needed timescale. it should be always possible, because phoenix can work with SPF less than 1 i.e. it can generate intermediate frames during the simulation.
i think it should be possible to retime exactly the simulation changing the time scale, the lower and the upper spf limit. all these values should be changed with the same coefficient.

[larex39]

so what is the equation if i have maximal step 4, spf up/down = 8 and i want to do it 4 times slower. Is it maximal step =1, spf up/down = 2?

[larex39]

Will also the foam react to this settings correctly?

[Ivaylo Katev]

yes, correct. and the foam should react to this as well

[larex39]

So I tryed some slow-mo tests simulations and I find that maximal step must be the same as in normal speed simulation. Not 4 times lower. But the problem what i have is the foam. In my simulation i have a part where the foam is throwed away and maybe 5 frames is in the air and failing back in liquid. But in slow-motion sim (0,25 time scale) the foam is flying only 2 frames in the air, so it looks like it is heavier and the movemet is realy fast. The good think is that liquid seems to be same like normal speed simulation. So if there is no workaround about slow-mo foam, I tryed to use only foam from my normal speed simulation with playback 4x lower together with regular slow-mo sim.

[Ivaylo Katev]

So I tryed some slow-mo tests simulations and I find that maximal step must be the same as in normal speed simulation

absolutely, my mistake that i didn't see you mentioned it together with the SPF limits. only the timescale, and both the limits have to be changed.

But in slow-motion sim (0,25 time scale) the foam is flying only 2 frames in the air, so it looks like it is heavier and the movemet is realy fast.

this seems to be a bug, i should check it.

p.s. i cant reproduce it, seems like the foam is simulated properly. i did a foam in the air with script and left it to fall slowly. with time scale =1 it reaches the floor for 120 frames, with scale=0.5 it reaches the floor for 240 frames

[larex39]

try some wave where foam will be throwed to air, sticked to the glass and slowly falling down. My time scale was 0,25 and it was realy different

[larex39]

Also in my sim i had 0.5 gravity not 1.0 and my foam parameters was: size=0,1 size_variation=3,0 size_distribution=400 B2B=8000 Rising_limit=7,0 Falling_limit= 20,0 sticky=0,0

[TSR_trix]

It would be great to also have this option to simulate sub steps. Then there would be no need to change any SPF value, especially in simple smoke and fire simulations?

[Ivaylo Katev]

sub steps = SPF (steps per frame)
just different name

[TSR_trix]

Ah darn sorry, of course.
I was thinking a simple way as it is in Maya fluids with just one parameter, but yes this is the same.