Page 1 of 1

Rigged Arm full of liquid - Question

Posted: Thu Jan 18, 2018 11:37 am
by angel_airlines
Hi Guys,
Im using the RFlow plugin for C4D 2.01 and I want to achive a solution for an animated arm (it is flexing) that contains a fluid that stick inside the arm.
The idea is to make a liquid animated arm that rotatates.

I've tried the fill emiter, and it works well for filling the inside of the arm but the fluid doesnt remain in the inside as the arm flex (geometry rigged). It escapes from the inside.
The arm has a volumen tag and a collider tag as well.

any idea on how to achive this result?


Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 4:10 pm
by Forester
This is a common task in Realflow, and there are several ways to retain liquid within a moving object.

The best way that I know of is to use a couple of Tractor daemons (maybe four of them) positioned around the moving object (the arm). The daemons need to be animated to move with the arm's movement. If they move with the arm, they can keep the liquid within the arm as it moves.

The reason that the Tractor daemons are a good solution is that you can adjust their force during the animation in any manner that suits your needs. You can weaken the force over time to release the liquid upon point of impact, or more slowly or more quickly, as you need. You can strengthen the force to push the liquid downward during the animation, or upward, or wherever suits you. So the Tractor daemons coupled to the object you want to move provide many control options during an animation of a moving object.

Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 5:09 pm
by angel_airlines
Hi Forester,
thank you for your answer. It is a clever approach.

By this time I have achived a decent result using the magic daemon and a backed PLA version of the rigged arm, so the magic daeomn pushes the particles to the arm suerface while this is animated, but... I would like the fluid fills the arm more than covers the external surface.

Your solution looks like that might be better but I wonder how could I help the fluid to shape fill the arm, so they are later helped by the tractors to move in synchro with the animation.
Would it be with a collider tag?


Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 6:49 pm
by Forester
I don't think you need the collider tag. But I'm not sure that I understand the question entirely. Are you attempting to "fill" the arm with fluid during the simulation? Is it completely filled before you begin the simulation?

Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 7:52 pm
by angel_airlines
The arm geometry get filled with liquid as it animates.
It´s like it is filled with liquid while the animation of the arms happens.... that is why the magic daemon was a good first solution.

The problem comes when I want to find a way to "fill" and not to cover it with the fluid. The magic daemon covers the geometry but leave the inside of the geometry empty, even reversing the normals of it, it doesn´t seems to work.

I have tested adding both a collider and a volumen tag to the geometry but the particles escape from the interior when the arms moves, so they only remain inside the volumen while the geometry is not moving....

Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 9:45 pm
by Forester
Aahhhh! Thank you for the clarification.

Ok, you should have no difficulty using your emitter to fill the arm during the animation, so long as your Tractor Daemons surround the arm for its full length, and are animated to closely follow the movement of the arm.

If you are not experienced with the Tractor Damon, it woul be a good idea to use four Daemon, to create a "box" around the arm. Change the lengths of the F1, F2,..F4 arms by changing their Force values. You may have to additionally adjust these values to keep the liquid inside the arm.

(By the way, if you are using the Dyverso Solver, also make sure that the Object Interaction - Surface Offset value is set to something other than 0.0. In practice, it should be given the same value as the Cell Size value. And for this kind of project, if you ARE using the Dyverso simulation, you will get more controllable results with the SPH particles in place of the PDB particle type. Both these things are important for keeping the liquid within the container.)

Finally, you probably should turn on all the Force Field Displays so that you can really see how the Tractor Daemon forces are working with your arm object. You can fine-tune any adjustments you need and see what you are doing when those displays are on. Of course, turn them off for your examination of the sim as a whole while running.

After these basic arrangements, you can work on reducing the Cell Size if using Dyverso to get a more finely detailed result. And you can increase the Sim Substeps to something like 12/200, or maybe something between that and the default.

Re: Rigged Arm full of liquid - Question

Posted: Fri Jan 19, 2018 11:36 pm
by angel_airlines
Thanks for your reply.
Monday morning I will try to follow your steps at work.
I will let you know how it goes...

by the way... any idea to help me with a milk fluid + mesh? ... 105#p55105

Re: Rigged Arm full of liquid - Question

Posted: Sat Jan 20, 2018 10:21 am
by Forester
You've checked my request to you on that thread?

Re: Rigged Arm full of liquid - Question

Posted: Mon Jan 22, 2018 10:30 pm
by angel_airlines
The filling is now working quiet alright, but I’d like the fluid not to be 100-% inside the geometry of the arm so I can get some fluid (probably becoming trendlis later) escape from it.
Not sure if playing with Min and Max steps is gonna give me this approach (I hadn’t being able to make it happen) or is maybe the cell side and the stickness to the surface the proper approach to let some pericles escape from the geometry (obviously with creative purpose)