Workflows for character facial rig with particle interaction

[dkrelina]

I wanted some feedback on a possible workflow.

I'm trying to find a way to create a liquid-like animation effect where a piece of geometry is partly controlled by a basic animation rig, and partly controlled by particles.

My goal is to design a character, where the skin of the character moves like jello and the facial features "swim around" on the surface of the geometry. Inspired by this image.

I was thinking a good starting point would be to figure out a way to take two objects (say a rigged face and a solid block of jello) and use particles to create a dynamic mesh (a single continuous piece of geometry) that merges the two. I imagine I would need to use particles to achieve this?

This video shows how it's possible to merge two spheres into one seamless mesh.

https://www.youtube.com/watch?v=ttmch_uhP4A

In my case, I would like to merge the face geo with an arbitrary piece of geometry (a jello block) and have the face "ripple in and out" as it moves through the block.

I'd like to stay away from simulations at this point. Keep things simple and experiment with dynamic meshes. What are these particle-generated meshes called? Is there a name for it in Maya?

[Roland.Reyer]

I'm not sure if it is necessary to use blobby surfaces.

What kind of animation are you planning?

Do you want the liquid flow from the characters head and arms and carry a semi solid face with it?

Or do you want the liquid stay in place like in the image and the face is animated and the liquid is just moving a bit?

[dkrelina]

Thanks Roland,

Bottom line is that I want to be able to have keyframe control over a dynamic mesh... to create an animation rig for a mesh that has changing vertex count. Obviously traditional skinning and weight painting won't work on a mesh with changing topology.

I was thinking something might work were I could create each facial feature as a separate rig, and then have the particles/blobby surfaces wrap to, or be influenced by, the rig geo. As the liquid sloshes around, the particles could "stick" to the facial features when they get close, perhaps under a pre-defined falloff radius.

I want to be able to

1. Move the facial features around independently, make them look like they're floating in a medium.
2. Respect the dynamic movement of the liquid in some areas (have pieces breaking off, or colliding with other surfaces, etc.) and have rig control in other areas.
3. Find a way to "paint weights" on dynamic mesh that has changing vertex count.

[mspeer]

Hi!

You already have the right idea.

Create the animation with separate object(s) and then have the fluid/particles flow around this object(s) driven by dynamics/fields.

[Roland.Reyer]

You could try to create a combined geometry from all shapes (face and the rest of the liquid shape) and do nParticles->Fill Object.

Then you have a volume that you can Wrap deform (geometry deforms particles).

If you remove all forces from the deformed particles then you can use them as a goal for a second particle object that does the quivering etc.

What's the storyboard like?

Is there really no way to fake it with softbodies?

[dkrelina]

It's for a personal project without a locked storyboard. I'm mostly trying to assess what's possible and plan a workflow.

I would like to find a way of creating organic movements that ripple realistically -- possibly breaking the topology -- which is why I feel like particles may be my only option. For example, I wanted the eye to sink into the liquid, disappear completely, and then resurface somewhere else. When it appears and disappears, I want the liquid around the edge of the eye to react in a realistic way, to make it look as if the eye is displacing the liquid, pushing the particles out of the way and getting that surface tension effect where you get a smooth transition between two objects.

Or if the fluid has higher viscosity, I want it to react like this.

I also wanted to create convincing rippling effects that emanate from the contact point.

I remembered this effect made possible with ferrofluid. Notice how the spiky shapes ripple in and out of the fluid and notice the surface tension between the individual spikes. I would like to do the same with the facial features.

Using two particle objects and using one as a goal sounds like a great idea. I have not done this in the past, so I'm unfamiliar with the process. Is it possible to have more than one object as a goal? For example, have the mouth, nose and eyes as separate goals, and then animate their influence on the overall system. Is that possible?

[mspeer]

Hi!

"I'm mostly trying to assess what's possible and plan a workflow".

Then try out what might work and find the right workflow for you. It's not uncommon that in some cases research and tests can take more time than doing the final animation. In 99% of all scenarios there are multiple solutions that all have their pros and cons. Especially in this case you should invest more time for tests.

[dkrelina]

Agreed @mspeer. But sometimes it's nice to have someone to hold my hand 🙂

I actually really enjoy mulling over these complex technical problems in a meandering and gradual sort of way through thought experiment. Comparing notes and seeing how we each would approach the problem. Like a cafeteria menu, glancing over the counter at the different options without being too locked into one approach. Let the ideas to sink in until I see a clear path and, when the time is right, take the deep dive.

But yes, even with all that planning, there's obviously a lot that can only be figured out through hands on experimentation!

[mspeer]

Hi!

No problem. This forum is a user to user forum where also ideas can be shared.

I hope that the rough ideas from @Roland.Reyer and me help you further with this.

Of course i could offer more details about general problems you may undergo with this project, different workflows and possible solutions, but then i had a lot to write.

Just some some points i want to add without going into detail

1. Don't confuse looking "real" with looking "good/plausible".

2. For high quality fluid simulation in Maya there is no other option than Bifrost.

3. Sometimes a manual animation is the better option.

[dkrelina]

Thanks @mspeer.

This was actually one of the things I was questioning... the nParticles versus Bifrost debate. Both fluid systems are relatively new to me and I was wondering whether it would be better to devote my time to learning one or the other.

Based on what I describe here, do you agree it's better to start with Bifrost?

As for manual animation, sometimes I wonder whether it might be interesting to use particle systems as a tool for generating blendshapes. To run the simulation, go through the cached frames and extract individual mesh shapes to wrap my master mesh. Basically use the simulation process as a modeling tool and incorporate them into a rig.

Do you see this being possible with Bifrost and/or nParticles?

One more question... how would you achieve the "surface tension effect" with manual animation? The effect where two objects are separate, then come close together and then the seam between them becomes smooth?

[mspeer]

Hi!

nParticles versus Bifrost - you should know both, they are very different.

Your project lacks a lot of detailed information so i can't recommend anything particular.

- How long is the animated/rendered sequence?

- Movement area for animation/simulation?

- Real world size, amount of animation/simulation detail?

- Render resolution, detail?

- Fluid properties, what type of liquid?

- Speed of animation, motion blur?

- Cartoon look, or "real" look for render?

...

If you have a specific question about a tool in Maya i am glad to help, but i don't have the time to go through all options for this project.

These are the tools that may help you:

Polygon objects, Joints, Dynamic Fields.

Animated Textures, Deformers, nParticles, Maya Fluids, Bifrost,

and of course scripting.