Ice Cube Drop..NEED HELP!!!

Show us your Realflow WIPs
shaun_michael
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Joined: Sun Sep 10, 2006 8:04 am

Ice Cube Drop..NEED HELP!!!

Postby shaun_michael » Mon Jan 15, 2007 8:16 pm

Hi Anthony,

Parenting
Fairly straight forward really. If you're parenting say the scaled down volume daemon, then set it up so that it fits snuggly just inside the cube, as mark suggested, then, in the node options for the killer you'll see, at the bottom, "parent to:". Click on that and choose your object.

Attractor Daemon
Add one to your scene and you'll see the arrows point inwards with a positive value. bang in a negative one and the arrows will point outwards and should repel things. I believe these work on both fluids and objects so if you went this route you'd have to make it an exclusive link to your objects ensuring you deleted the object in question out of the global links tree.

Mass Settings
Realflow defines a default mass for an object based on it's volume. As you can see, from your ice cubes, sometimes this is not nearly close to what you want because the mass setting of your objects is measured in Kg. So a setting of 30 will give you 30 Kg ice cubes.

IMHO I would steer clear of the daemon idea as ultimately you probably wont get the organic look you're after. Dont mess with your pressure settings or you'll end up with a fluid that doesn't behave like the one you're after.

I think you're right going with the back and forth sd idea with a low res fluid to get the motion, but you'll still need to address the buoyancy issue first.

Good luck, looking forward to seeing some WIP's.

Shaun


overload
Posts: 176
Joined: Mon Dec 18, 2006 5:00 pm

Ice Cube Drop..NEED HELP!!!

Postby overload » Mon Jan 15, 2007 11:00 pm

Cool, thanks Shaun :). I cloned, scaled, and parented all my cubes for the kill collision. I also lowered the mass to 15, so they will at least go into the water, just not sink like rocks. Seems to be working ok so far. I'm going to let this run over night. Since the final animation only has to be about 100 frames long, I just want the cubes to not sink straight to the bottom....but I will figure out the buoyancy later after this project is done on my own time. Hopefully tomorrow I can post some of the results. Thanks again guys, you helped me out a BUNCH. :)

Anthony

overload
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Ice Cube Drop..NEED HELP!!!

Postby overload » Tue Jan 16, 2007 3:56 pm

Well quick update. I think this sim turned out alot better than the others. Even with the parented kill object, I still get strange mesh spots inside the cubes that pop on and off. I may have to render with a texture map on the cubes instead of using a glass/water shader. Any comments please!! :). This isn't a render just a preview from max. Thanks again everyone.

http://www.overloadgraphics.com/SpashPreview.mov

Anthony

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dalo
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Ice Cube Drop..NEED HELP!!!

Postby dalo » Tue Jan 16, 2007 5:07 pm

hi anthony
looks better now..:)
it still bounces a bit, before ice cubes hit the surface.
is the fluid settled?
sometimes it still bounces, then it helps to have a speed daemon with limit and keep turned on. this one kills all movement, turn it off, when the cubes collide with the surface.
also the mesh seems to penetrate the cube(more collision distance maybe?), though this one really goes on and off....strange thing.
the side of the mesh which is close to the glass is too round. maybe the mesh filtering is too strong or you need more compression. i know that problem too from my own projects, but havent found a solution besides resimulating with far more particles or other less viscous fluid settings(an ffd box used on the mesh can imrove that but with a lot of motion and bouncing this isnt really an alternative).

shaun_michael
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Joined: Sun Sep 10, 2006 8:04 am

Ice Cube Drop..NEED HELP!!!

Postby shaun_michael » Tue Jan 16, 2007 6:27 pm

Hi Anthony,

Glad you're making progress.

What's your compress factor setting for this sim? Upping this before you settle the fluid may help you in minimising the bounce assuming you've settled it completely at first - I'd suggest somewhere like 10,000 or more, but it also depends on your internal pressure setting.

Even with the parented kill object, I still get strange mesh spots inside the cubes that pop on and off.

Where did you end up with particles? Inside your killer objects or between them and the parent object? Curious.

Keep going, the mass/motion of the cubes looks convincing, very nice. I cant help thinking there'd be more of a splash though :)

Shaun

overload
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Ice Cube Drop..NEED HELP!!!

Postby overload » Tue Jan 16, 2007 6:34 pm

Thanks :). Well thankfully (in the interest of time) they canned that part of this project, so I don't have to stress about finishing this right now. But I appreciate you guys helping me out on it. I will finish it in my own time hopefully this weekend, DAMN THE MAN!! :)

Anthony

overload
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Joined: Mon Dec 18, 2006 5:00 pm

Ice Cube Drop..NEED HELP!!!

Postby overload » Tue Jan 16, 2007 6:45 pm

shaun_michael wrote: Hi Anthony,

Glad you're making progress.

What's your compress factor setting for this sim? Upping this before you settle the fluid may help you in minimising the bounce assuming you've settled it completely at first - I'd suggest somewhere like 10,000 or more, but it also depends on your internal pressure setting.

Even with the parented kill object, I still get strange mesh spots inside the cubes that pop on and off.

Where did you end up with particles? Inside your killer objects or between them and the parent object? Curious.

Keep going, the mass/motion of the cubes looks convincing, very nice. I cant help thinking there'd be more of a splash though :)

Shaun

Woops sorry I just saw your post :). By compression do you mean my internal and external pressures??? Or am I missing something major here? I let the particles settle for some time, with and internal and external pressure of .5, and a viscosity of 1. I also had the Kspeed daemon on only when they were settling with keep and limit turned on. Your right about the splash, I expected more. I turned the mass down to 15 on the cubes...i may try 20-25 since 30 made them sink to the bottom still.

I have no idea where the mesh popping inside my cubes in coming from, but I am definitely not getting any particles inside the cubes and sloshing around anymore. I set my killer cubes to .98 scale and parented them... This project seems to be one that I will have to revisit when I get some free time, I just got hammered with 3 new Verizon commercials, one has tons of fire effects. :O Not sure if RF is overkill for that, I may stick to digital fusion. Thanks again Shaun. ;)

Anthony

shaun_michael
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Ice Cube Drop..NEED HELP!!!

Postby shaun_michael » Tue Jan 16, 2007 7:33 pm

Hi Anthony,

By compression do you mean my internal and external pressures??? Or am I missing something major here?

I think your day is about to get a little better :)

Yes, you are missing something major here. The compression parameter can be found in your preferences under the simulation tab - it used to be elsewhere in older RF incarnations, but they've tucked it away out of sight, but IMHO it's one of the most important parameters when trying to get low viscosity fluids.

Basically what it does is compress your fluid which, to kind of put it in my own words "seems to compress the particles as a whole mass." If you like, it's constraining the internal pressures of the particles en masse. I hope someone else can come up with a more eoloquent (and more accurate) desciription. Bottom line is low compression settings (like the defaul 200) still leave lots of spring in your particle mass, meaning it bounces about. A high compression paraneter (like 8000-10,000 makes your fluid far less viscous - runny :)

I've not tested above 10,000 for this setting but would be interested in the results - I'm sure extreme values would lead to instability though.

Pressure settings with a ratio of 1:100 internal:external seem to work well to obtain low viscosity, and also making your particles slightly lighter (lowering the desity setting to say 750-800) may also help you obtain more of a splash without you having to change the the mass of your cubes. You may also find the cubes will act differently in these fluid conditions so test it a bit first. Oh, and if you lower the internal pressure to a one hundredth of the external, you'll need more particles to fill the volume as they'll compress together nicely. One upside of this is a tighter mesh :)

I would advise, once you've changed your prefs that you save your scene, close it and reopen before running the sim as I've found some preference settings don't apply until after a restart. Also, always bear in mind that this setting will be there for every sim afterwards unless you alter it on a sim by sim basis.

Hope that helps out. BTW, you can find me messing about with pressure and compression settings in this thread.

Shaun

overload
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Ice Cube Drop..NEED HELP!!!

Postby overload » Tue Jan 16, 2007 8:05 pm

omg..I've been wondering about the damn springyness I kept getting. I tweaked the internal and external pressure for days, with no change in the way my fluid was bouncing around. I'm so glad you pointed that out :). Would have been nice if either Digital Tutors, or even Nextlimit made it a point to show this to people. Hopefully the new Gnomon dvd will go over the "hidden" parameters that no one talks about. I will give that a try again tonight and see what it does with the value's you suggested. Maybe I can get them to still use this in the project.

I guess RF is still such a new thing that not many people know what the hell is going on, and learning it is all trial and error right now from what I can tell. CFD is something that still has a long way to go, but we are getting close :). Thanks Shaun, I will run another sim later and see what happens.

Anthony

shaun_michael
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Joined: Sun Sep 10, 2006 8:04 am

Ice Cube Drop..NEED HELP!!!

Postby shaun_michael » Tue Jan 16, 2007 10:46 pm

Good luck Anthony. Keep us informed as to how you're getting on. Be careful with the density setting - you dont want it to splash too high (or perhaps you do). Low res testing first.

Cheers,
Shaun


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