Help with liquid crawling up figure's face effect

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Posts: 1
Joined: Tue Sep 13, 2016 10:00 pm

Help with liquid crawling up figure's face effect

Post by Kukov » Tue Sep 13, 2016 10:02 pm

Hello everyone,

I'm working on a personal project for which I'd love to create a few shots with Realflow. I've spent the last few weeks trying to get this shot right and I still can't do it - it's driving me crazy! Would love to get some advice from some of the talented people here.

Before I get into the specifics, I want to prove that I have been trying to learn this on my own. I've found it's usually not cool when someone new comes in who clearly hasn't done their homework and expects others to do work for them. That's not me - I HAVE done my homework. I realize Realflow is a complicated, nuanced program, so I've spent the last few weeks playing around with it and trying to gain a basic understanding of how it works. For example, I've learned how to use the SD exporter from C4D to bring in a project, make sure my Simulate FPS settings are correct (simple, but took me a while to realize!), how to create a simple simulation and affect it with some of the daemons, etc, how to import the mesh back into C4D, ensure I have it exporting as .bin instead of .abc, learned how to use the keyframe animator for parameters, learned the importance of the F1 button, etc. I'm no pro, but I know enough, I think, to pull off this shot - which is why it's driving me crazy that every time I think I've got it some new problem crops up.

I'm looking to create a shot where a black oil/goo slowly crawls up an individual's face. The idea was inspired by this fantastic piece:

I tried following those settings exactly and I didn't get a good result - then I started experimenting with my own settings, but still am not there. I even tried writing to the guy who created the video but he never responded.

Here's a link to the original version of my shot - hopefully you can imagine the effect I'm trying to achieve: ...

In the example I'm working off of, the guy used several photos to projection map the person's head into C4D, then exported the whole thing with lighting and the mesh from C4D. I don't have the photos to pull that off, so I'm hoping that I can just export the RF mesh as it crawls up a dummy figure, take that and comp it in After Effects on top of the original shot, and be sure to crop out any part of the mesh that "doubles back" or overlaps in an incorrect way in 3D space. So all I'm trying to do is get a simple goop to crawl up the FRONT FACE of the figure.

Here's what my latest attempt looks like, obviously at a very low RF emitter resolution: ...


Emitter - Square:
Resolution = 0.3
Density = 1000
Int. Pressure = 0
Ext. Pressure = 1.0
Viscosity = 10
Surface Tension = 5
Speed = Keyframe animated to stop emitting roughly 1/3 into the clip's runtime

Polygon size = 0.02
FIELD - Radius = 0.04
Filters ON
Filters = Smooth x2
Filters - Thinning = 0.1
Relaxation = 0.1
Tension = 0.1
Steps = 50

Magic Daemon - on object figure that I want fluid to envelop
Affect: Force
Approach str: 10
Escape str: 15
Magic Mode: Nearest Face
Random Within Face = NO

K_Speed Daemon - without this the whole thing happens way too fast, can't figure out any other way of slowing it down, tried drag force but found this easier
Min speed = 0.1
Max speed = 1.5

Sheeter Daemon
Min cavity size = 2.0
Everything else default

Two K_Volume objects to kill the particles that are going underneath and behind my object, don't need to see those particles and figured render would be faster without them.

Here are my problems and where I'm thinking I need help:

1) The liquid doesn't crawl all the way up the figure's head. How do I do this?

Explanation: The liquid goes up to the neck area, then just stops. I suspect this has something to do with the 3D model of the head I created - I'm guessing the "force" of the liquid isn't enough to propel it above the lip of the chin, even with the Magic Daemon. How can I have it continue to crawl up the figure naturally? I tried using a gravity object to help pull it up and around, but then it went too fast, it detached from the figure and started floating in space. After hours of tweaking I got it to crawl up, but it spilled around the side of the head and crawled up the ears instead of the front of the face. Next I tried using an Attractor object that I put right at the forehead of the figure in the hopes it would pull the liquid up there, but that too didn't work - the liquid just went up the side, around the ears, instead of the face.

2) At higher resolutions the liquid starts to seep INTO the solid object and I get renders of liquid wrapping around the INSIDE of the object as well as the outside. How do I fix this?

Explanation: This is the straw that broke me - I was resigned to just use an export where the fluid crawled up the chest, and I was ready to export it, but I noticed when I did a higher resolution export, something like Res = 10, the particles somehow crept INTO the object and would ruin the effect. After dozens of previous attempts I had never seen this before and now I can't get rid of it. How do I fix this? And yes, I am certain that the model/object I'm using has no holes or gaps in the bottom for anything to seep into.

3) Roughly 80% of the way into the render the mesh starts to vanish - you can see it happen in the link above - the particles are still there, but the mesh begins to fade away. Why? How do I fix this?

Explanation: No idea why the mesh starts to vanish even though the particles are there, but I'm guessing this has something to do with my Smoothing settings, my Sheeter, or my K_Speed Daemon?

4) Is there anything else I should be doing to make this easier on myself, or to get a better final product?

Explanation: I'm more than happy to scrap the whole thing and start over from scratch if someone has some ideas for how to do this in a more efficient, effective manner.

Needless to say, I'd love to get any tips for any of my questions above, or just the project as a whole. Thanks a lot for your help!
Posts: 32
Joined: Thu Jan 05, 2012 11:49 pm

Re: Help with liquid crawling up figure's face effect

Post by » Tue Oct 25, 2016 5:49 pm

Start by working on that model. Make it one surface, not different pieces bunched together, make sure its correct: no bad polys, no seams, no overlaps, normals uniform and pointing out, and that it matches your reference! You have no hope of getting the footage and the effect to comp if the model is not accurate, and that model is not accurate. Plus improved geo will help the magic daemon do its job.

Is your internal pressure set to zero? Give it something even if low. Zero is no good.

If speed is an issue change your frame rate (under simulate>options) to something higher. Just like slo-mo camera rates: if you are doing animation at 30fps and you want it 5x slower use 150fps.

Don't worry about the meshing until you get the particles doing what you want. You are just wasting time meshing which could be spent simming.

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