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Hokmah

Foam from the bath

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I'm starting working on short sequence where the guy is dancing in the bath and I have to create foam in the bath which will interact with this guy and move out of it. Dont have any hip file now so can't show the way in which I'm going on. Can you guys give me any tips for this thing and how should I start with it? Never try it before.

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you should give us more detail...is the guy live footage or 3d? same for the rest of the setting. if everything is 3d, than it's basically just a (flip) sim that you have to adjust to behave like foam.
if the shot is live footage you'd have to begin with matchmove. track the shot, create and animate a 3d proxy for the guy (needed for collision, etc), then start with sim

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3 hours ago, 3dome said:

you should give us more detail...is the guy live footage or 3d? same for the rest of the setting. if everything is 3d, than it's basically just a (flip) sim that you have to adjust to behave like foam.
if the shot is live footage you'd have to begin with matchmove. track the shot, create and animate a 3d proxy for the guy (needed for collision, etc), then start with sim

yeah my bad and forget to give more detail of this project. Everything will be in 3D so there will be hipopotam dancing in the bath full of foam so need to create interact foam with my hipopotam. In attachment there is hip file with the way which I'm looking for to create this foam. The foam have to be stylized on Disney animations. Below two references which I've found on the internet.

foam03.hipnc

post-15230-0-50532000-1457556086.jpg

post-15230-0-03947400-1457556085.jpg

Edited by Hokmah

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Honestly I think you could just do a high viscosity Flip sim but instead of meshing it afterwards you simply instance spheres to it with varied sizes and shading attributes.

Maybe something in the Flip solver too that randomly deletes 0.1% of the particles per frame to give the effect of popping bubbles.

Use that in combination with a fog VDB made from the Flip fields to help get the white cloudy look internally and I bet you're close already just with that.

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16 hours ago, Kardonn said:

Honestly I think you could just do a high viscosity Flip sim but instead of meshing it afterwards you simply instance spheres to it with varied sizes and shading attributes.

Maybe something in the Flip solver too that randomly deletes 0.1% of the particles per frame to give the effect of popping bubbles.

Use that in combination with a fog VDB made from the Flip fields to help get the white cloudy look internally and I bet you're close already just with that.

I think flip will be a little complicated in this case but this is the only my opinion obout it so I will try with sof body or something like this. I have few pieces of foam modeled in Houdini. Now it only need to interact with model like a cloth or something like that. Here on Toy Story sample you can easy see it where the foam is on her and moving like a FEM object or something...

Toy Story 3

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56 minutes ago, Hokmah said:

I think flip will be a little complicated in this case but this is the only my opinion obout it so I will try with sof body or something like this. I have few pieces of foam modeled in Houdini. Now it only need to interact with model like a cloth or something like that. Here on Toy Story sample you can easy see it where the foam is on her and moving like a FEM object or something...

Toy Story 3

Yup you could go that route too. If you have a polygon object behaving nicely on your character, you could have your rest frame, scatter points on it for instancing spheres to, and then use the PointDeform SOP or several other ways to stick those points to the geo representing your cloud of foam.

Then you could duplicate that foam geo a couple of times with different Peak SOP settings applied, maybe a mild Mountain SOP, and then you could have a few layers of bubbles working for you that way and get some depth. Then do a Fog VDB from your polygon foam to fake the depth past where your bubbles run out.

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The specific example of the top of her head was done with a lattice and spring chop for the motion. It has a strength falloff based on the distance to her head to mix in the spring amount. So basically, lock the foam points to the geo (using point deform), lock a lattice (box) to the head using point deform. Use spring chops to drive the lattices points. Use the spring-ifyed lattice to drive the points. Mix position based on distance to the head. (FEM would also work well though!)

We used that setup on a few shots, but most were fully simmed using a custom spring solver in pops. Each point was connected to the ones around it with primitives which acted as constraints (very similar to bullet constraint networks). The grain solver would probably be suited well for this. 

Rendering was a custom shader. It was riSpheres with displacement that used a pointcloud lookup to create the interfaces between the points. http://www.glassner.com/wp-content/uploads/2014/04/CG-CGA-PDF-00-11-Soap-Bubbles-2-Nov00.pdf was referenced a fair bit as well as some other papers iirc. We did use a volume to create a depth attribute on the points, and we used that in the shader a fair bit as well. 

There is a short siggraph talk paper on the short film available, but it's behind a paywall here: https://dl.acm.org/citation.cfm?id=2504480

Edited by Solitude
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Thank you guys for your all useful tips for this king of simulation. Here is zip file with hip and example bgeo file for this simulation on which I'm working. Still have a little problems with frictions. Would like to constrain bottom of the foam geo to the ground and interact only on the higher parts of it.

fem_foam.7z

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After few test I have enough deformation effect for my project and now have next problem with shader now. You can check in atachment screens of bubbles layer and volume layer + hip file with tests. I would like to achieve this kind of foam like this little monster in this ad: YOUTUBE FOAM

Do you have any idea guys how to create this kind of foam? I have geometry on which I'm usuing a little smoke shader + scatter with spheres with glass material but still so far away of this look.

foam_09_shade.hipnc

test_bubbles.jpg

test_volume.jpg

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