Faking a water level/line in an IV Bag?

[goesb]

Hi guys,

I've searched for a few things regarding this problem, and haven't found much. I have to flip an IV bag over and when this happens the water level needs to stay horizontal if that makes sense. Other than running a time intense water simulation with Realflow or Glu3D, I'm having a hard time finding a way to do this.

It doesn't need to look perfect, but I need it to look as though there is a water line in the bag with a few bubbles animated here and there. I tried using an ncloth surface with a flat passive collider to 'flatten' the top of the ncloth out, but to get the detail needed Maya gets pretty slow, and I'd probably be better off running a real flow sim.

Then I thought I could possibly have a poly plane intersect the water mesh, and use a ramp to make the mesh transparent at the point the water line should be. This would work but I can't think of a way to make the surface at the top renderable – the water would look as though it's hollow from the top view.

I hope this makes sense. Any suggestions are greatly welcomed.

Thanks!

[david-larsh]

maybe some way to booleen every frame, i'm very amauter so not really sure why i'm trying to help.
if you are using maya i remember a way to booleen at render time, that would seem your best option. can't really say how as my computers broke and i don't have maya in front of me.

[joojaa]

Other than running a time intense water simulation with Realflow or Glu3D, I'm having a hard
time finding a way to do this.

well you will find that running this simulation is indeed hard even with a fluid simulator. In fact insanely hard to get right, because of the counter presure/elasticity of the container. So unless you know how to exactly do this in fluid sim from piror experience dont expect it to be easy.

But alat threes a very easy way, that is about 200 times easier than with a fluid simulation to do this all you need is 2 blendshapes. maybe a boolean  for final taouches (but not needed) or so.

[goesb]

Hi guys,

Thanks for the tips and suggestions.  Joojaa you are very right.  I'm actually pretty experienced with Realflow, and it's always a difficult chore to get things just right, but fluid simulation is inherently complex so I anticipate this everytime.  For this project though, it's not required and the client isn't paying for fluid simulation anyway.  it just needs to be a quick and dirty effect. 

Right now the boolean trick is working fine.  I'm interested in the blendshape idea though.  I'm not sure how I would go about that though. I need the water level to always be flat on top.  Seems that I would have to create a ton of blendshapes to keep the surface flat on top – I must be missing something. Can you elaborate on that.

The bag has to flip upside down and the inside of the bag is pretty complex.  It has two tubes sticking out of the bottom which will be filled with water.  Sort of like a cow utter.

I've also considered trying the PhysX fluid sim by nVidia, not sure if this is just as complex as running realflow though.  Again it doesn't have to be perfect water, but if there's a quick way to run a fluid sim I'd love to do that.  That would make the client uber happy.

[joojaa]

ahh no you dont need the blend shapes for the water level. you need them for the bag, when the bag empties it crumples down. So you need a uncrumpled bag and a crumpled one*. Then just keyframe the blend weights over in ramp like fashion.

Now if you make the bag out of 2 nurbs surfaces (you may as well do it because its made out of 2 flat surfaces), you dont need a boolean just take a curve on surface projection on each surface and loft between.

Use boolean for doubles, use nurbs spheres that boolean with the surface and are surrounded by a sculpt deformer to make a smallish wave and bubble burst.

• 2 or 3 states should be enough. Now youd get the wrinkles to work out aswell. You can probably make it look as real perhaps even realer than with a quickly done  fluid sim.

[goesb]

ok. Thanks Joojaa. I totally understand the blendshape part now.    That's exactly what I had in mind.

Now, regarding the nurbs surfaces, that's going to be an issue.  I totally agree with you that the bag is basically made of two pieces of plastic fused/melted in places to form the bag.  However, it had a lot of detail once I looked at it and I poly modeled the whole thing. That probably wasn't the smartest choice, but I'm faster at poly modeling and that's the route I chose.  This being said, I'd like to find a way to do what you are talking about with my current poly model.

Do you have any other suggestions?

[vikash-kumar--7]

I've been playing around with this boolean MR shader (created by Ledin Pavel) that might help.  Here's what a quick test produced:
http://www.youtube.com/watch?v=TiP3GUxjmbQ

Pretty sloppy dynamics I threw in there, but you get the picture.

Here's the shader:

http://www.puppet.tfdv.com/download/shaders\_p\_e.shtml

A tutorial:
http://www.puppet.tfdv.com/shaders\_p/docs/howtocsg.html