off-topic: viscous fluids using constraints (X-particles for C4D)

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ChristianZ
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off-topic: viscous fluids using constraints (X-particles for C4D)

Post by ChristianZ » Sun Dec 29, 2019 10:40 am

Hi

recently I was looking into viscous fluids options in Realflow and the overall impression is, that heavy viscous fluids are rather easy to do, such as marmelade, chocolate, dough, tar etc., or solid elastic objects that don't flow. What is harder (the fluid breaks up) are very slimy fluids such as paint/glue, cheese, saliva etc. One reason for that may simply be that the don't follow the classic physics of fluids in the sense that there is not only the connection between single molecules, but there is in addition a polymerization of longer strands.

In the plugin "X-particles" for Cinema4D there is an option to mix a fluid solver with a constraints mechanism that links particles together depending on the distance between them. Furthermore, the stiffness of these bonds and their breaking point can be adjusted. And that is how such a fluid could look like: https://youtu.be/HFyapR5AGGE
RF10.5 standard + RFC4D3, Mac&Windows

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Oldcode
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Re: off-topic: viscous fluids using constraints (X-particles for C4D)

Post by Oldcode » Sun Dec 29, 2019 12:38 pm

Hey Christian,

I've been trying to work with viscous fluids since RF 2012. The big problem for me was to get them to be sticky. I mean really really sticky. Your examples of pain or glue is very close to what I was trying to do.

I have found the new Viscous Material that they have with the newer version of Real Flow to have some problem, mostly because of the lack of a good sticky factor. In order to make the Viscous fluid stick to an object and behave like in your video clip, you have to set the object friction and roughness so high, the fluid does stick to the object, but then even starts crawling up the object, even against the force of gravity. I may user this for a Blob movie I'm thinking of where the blob sends out tendrils to absorb its victims, but for most situations, this is a big problem that kills the illusion.

To get the sticky and slimy to work its best, so far the best way to find it use...

1. Use Dyverso SPH
2. Set Viscosity to at least 200
3. Geometry Settings:

Friction 1.0
Bounce 0
Sticky at least 100
Roughness 0.1
Interaction 1.0

You can see how well this works in this test clip here...

https://www.mediafire.com/file/dwu37f9t ... y.wmv/file

I just finished a project using this method. The only draw back so far is Dyverso SPH takes longer to simulate out than the Viscous Material, and you need to increase the Subsets to deal with the ever so annoying "popping" particles.

I used to use the Standard particles with similar settings, but those take even longer to simulate, which is bad, but you can go in and remove rouge particles one by one if needed, which is good, but you can't do that with Dyverso. :cry:

Hope this helps.

Good luck,
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ChristianZ
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Re: off-topic: viscous fluids using constraints (X-particles for C4D)

Post by ChristianZ » Sun Dec 29, 2019 3:20 pm

Hi Oldcode

I saw your movie. It seems you have found good parameters for letting the swamp stick to that lady. Could be handy for other scenarios such as a spoon in yoghurt or chocolate :)
Regarding the viscosity of Dyverso-SPH or classic particles, the "poppping" particles that you mentioned are a real problem at higher viscosities, over 200. I can set the substeps to minimal=1000 and it still happens. It may be avoided with drastic drag and fps settings, but the sim then gets so slow it does not make sense anymore and you would rater use practical effects. Justin Bates recently released a commercial video tutorial series using X-particles for Cinema4D that seems to show some progress in this area of fluid simulation https://vimeo.com/ondemand/xpfluidsvol1
RF10.5 standard + RFC4D3, Mac&Windows

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