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Particle Fluid flow from animated character????

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Hey Guys

I am working on this project for my thesis and I still cannot get a nice fluid flow from my animated characters. Basically, I have the two characters made from liquid, but want the liquid to have a natural fluid flow from them. Right now, I'm getting a lot of time stepping where it looks like the fluid is emitting from the character (which is what its doing), but I don't want that look. I'm looking for something that falls more in line with Digital Domain's Bacardi Sundance Commercial. Here is the website for the Bacardi Sundance http://www.youtube.com/watch?v=qk8t6cHMzRY, if anyone has any suggestions I would really appreciate it. Thanks

PS: I already know that DD used a in-house method called Blobtacular, which, of course, I don't have access to

Chris

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Hi,

i would try preprocessing mesh before simulation and emitting fluid in specific areas like that:

waterBall5.mov

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Hey Owl,

Thanks so much for the reply, and your video is exactly what I'm looking for. But, I have two questions; One, what do you mean by preprocessing mesh (like bringing in mesh from Maya, etc.)? and two, how can you emit fluids from certain areas? Thanks again.

Chris

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Hey Owl,

Thanks so much for the reply, and your video is exactly what I'm looking for. But, I have two questions; One, what do you mean by preprocessing mesh (like bringing in mesh from Maya, etc.)? and two, how can you emit fluids from certain areas? Thanks again.

Chris

by preprocessing i mean doing some animation on mesh itself in sops with noise, lags etc.:

waterBallWire.mov

I used FLIP fluids - so it's particles and you can emit particles from surface that is masked by any attribute(like colour) :)

You as well might mask volume fluid emission by using predefined volume object instead of whole character

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Hey Owl

Thanks for getting back to me so fast....I think I know what you mean, but is there any chance you can send me the HIP file so I can see what does what. The only problem I see right now is that I want my entire character to be liquid, but only emit from different parts. I'm attaching some test screenshots of what I have so far. If you could take a look and let me know what you think I would greatly apperciate it. Thanks so much again.

Chris

post-6082-128888496202_thumb.jpg

post-6082-128888500933_thumb.jpg

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Hey Owl

I used the grouppaint node and applied that in the FLIP fluids and was able to emit just from that area, but it still doesn't look like your example. I'm sorry for asking sooo many questions, but I am in desperate need of help for this is a big step in my thesis. Thanks again.

Chris

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Hey Owl

Thanks for getting back to me so fast....I think I know what you mean, but is there any chance you can send me the HIP file so I can see what does what. The only problem I see right now is that I want my entire character to be liquid, but only emit from different parts. I'm attaching some test screenshots of what I have so far. If you could take a look and let me know what you think I would greatly apperciate it. Thanks so much again.

Chris

Yeah sure :) here you go

waterBall.hip

I've renamed nodes for better readability, thou ask if something is unclear :)

I would definitely increase substeps in your FLIP simulation due to fast motion and transfer velocity to emitted particles

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Thanks so much again!!! I'm going to look over the file this weekend and see what I can make from it. I'll let you know if I have any questions.

Chris

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Hey Owl

I've been looking over the file this weekend and I have to say it's a little over my head. I'm still pretty new to Houdini as far as VOP's go and don't know them too well. And, as far as the noise, etc., I don't think I need any of that because it will deform my character to the point of not recognizing it too well. I was wondering if there was a simpler way to get the same effect. I pretty much understand what does what, but using VOP's and applying it to my characters would be a little to complex for me right now. I love learning different techniques and will keep at it, but I'm on a pretty tight deadline right now. If you have any more suggestions, I would greatly appreciate it. Thanks again

Chris

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Hi, Chris,

vops are not that complicated, but in your case - you probably don't need noise that much.

All I really do in sops is masking by normal and velocity (as I wish to modify the parts of the mesh that are facing down with some falloff)

All you need is:

1. Create mask for emission of particles by normals*velocity (fluid is emitted from surface facing downwards and moving fast enough)

1b. Create attractors to tour characters to try to maintain shape before falling down (optional)

2. Create FLIP fluid, increase max substeps (since your characters are moving fast), emit particles wit probability of $CR.

2b. inherit velocity from emitting surface for more natural looking results

3. in surfacing sop - bring in character mesh and use "points from volume" node merge result with FLIP particles and surface it.

I've attached a hip without vops thou imho its harder to read :)

waterBall_noVops.hip

hope it helps :)

P.S. would love to see your results

Hey Owl

...

I was wondering if there was a simpler way to get the same effect.

...

Chris

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Hey Owl

Thanks a lot for the examples and feedback. I believe you are right, it will be simpler to use the VOP's instead of the point SOP's. I'm starting to understand how each one works. When I have a descent test to show i'll post it. Thanks again.

Chris

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Hey Owl

I was wondering if you could take a look at my file and see if I set it up correctly. I wrote out the particles to a ROP driver, so I, obviously, I can't attach those files, but I just want to know if the setup is correct. I feel like the velocity isn't working correctly and when I wrote out the particles to a ROP driver from the DOP import inside the particle fluid node (breath), it took 20+ hrs to write out 60 frames. It also didn't seem like it wrote out the fluid from the attractor for the character. I would really appreciate it if you could take a look and give me some feedback. Thanks again and hope to hear from you soon

Chris

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Here is the file...

Hi Chris,

I've made some quick edits (thou couldn't test it) and added some notes, I believe long simulation times you had were because of 2 flip solvers trying affect each other

here's the file:

Shot_2_resize_flow_boxer2_edited.rar

let me know whether it works out or not :)

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Hey Owl,

Thanks for posting the file...I've been working all day and havent had a chance to look at it, but I'm going to go through it tonight. I'll let you know how it goes. Thanks again for all your help.

Chris

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Hey Owl,

I'm looking at the file you posted now...the one solver works great. I'm solving now and it seems to be going quicker. But, I have three questions: One, in the particle fluid tab, why did you place a 'switch' node and whats its purpose, two, what are the 'points from volume' nodes and what exactly are they doing, and, three, would I have to place another 'object merge' node and 'points from volume' node, connect it to the 'switch' node to add my other boxer? Again, thanks so much for taking time out and helping me. Talk to you soon.

Chris

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Hey Owl,

...in the particle fluid tab, why did you place a 'switch' node and whats its purpose?...

...what are the 'points from volume' nodes and what exactly are they doing?...

...would I have to place another 'object merge' node and 'points from volume' node, connect it to the 'switch' node to add my other boxer?..

Hi, Chris,

switch node is to compare the results between simply merging in boxers geo and using points from volume

points from volume - fills given volume with points its like a 'scatter', but instead of scattering on surface, it converts your object to volume and then scatters points (you can dive inside and look for your self it a DA) btw, you might want to link it's stepping to your fluid resolution.

yes you should use another 'points from volume' node (since it converts to volume and you don't want a big volume primitive with small stepping)

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Thanks for the info...that's what I thought they did. Anyway, I have one more question (sorry!!!). I want to change the color of the fluid for the body, gloves, and shorts for both characters. Now that they are feeding into one solver and one particle fluid node, how would I go about that? Thanks.

Chris

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Thanks for the info...that's what I thought they did. Anyway, I have one more question (sorry!!!). I want to change the color of the fluid for the body, gloves, and shorts for both characters. Now that they are feeding into one solver and one particle fluid node, how would I go about that? Thanks.

Chris

No problem :) you can make separate sources for them and put them into groups, and assign colours before surfacing.

You can predefine colour on surfaces.

You just need to enable Cd attribute in 'particle fluid surface'

Check this example, ask if something is unclear :)

flip_fluid_color.hip

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