Meshing questions

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Thanos Kagkalos
Posts: 34
Joined: Tue Nov 28, 2017 11:09 pm

Meshing questions

Post by Thanos Kagkalos » Tue Dec 12, 2017 7:32 pm

Hi, some generic questions. I m not sure how to mesh my liquids. So far i get either noise mesh with detail result or very smooth with no much detail, its pretty hard to find balance.
See the link below, i attach a small test. The simulation has around 700k particles and 250k polygons. Sim on the left is flickering inside mesh, and sim on the left has no detail but liquid is very smooth. For example i had to push mesh smooth here to get a nice result at around 20-25 but i lost a lot of details.

video link: https://www.dropbox.com/s/ahzfbfoh6mud0rb/xtc.mp4?dl=0

So to my questions: How many particles is a good amount to have a detailed sim and same time a smooth mesh? And in general what is the average number of particles/polygons in a high quality close up eg. a macro drop with tendrils. I need a generic range to see if im doing it wrong or if its just a matter of raising numbers.

Thank u very much!
Thanos

Thomas Schlick
Posts: 178
Joined: Tue Aug 29, 2017 12:35 pm

Re: Meshing questions

Post by Thomas Schlick » Wed Dec 13, 2017 9:48 am

I totally agree. It really requires some experience to find a good balance between the different mesh parameters. The number of particles is absolutely sufficient in your scene. Unfortunately, it's very difficult to give global and common values for the number of particles, because personal demands, scene setups, and scales are simply too different. But I think you have a very good feeling for that already.

When I create meshes I normally start with "Resolution" set to "Medium" or "Medium-High".
Radius = 8 cm, but when I have lots of particles, as in your case, I also start with 5 or 6.
Smooth = 5. That's my default value and I change it in the end when I do the last changes, but I normally don't go higher than 8.
Thinning is also very important and instead of high smoothing I try to find a balance between Radius and Thinning. Maybe you want to start with something like 0.3 or 0.4.

For your scene I'd say that a polygon count of around 400-500k should give you good a result. The more polygons, the more details you will finally see. I don't know, maybe you've expected more, but I hope anyway that these values will help you to get a better feeling for meshing.

Thanos Kagkalos
Posts: 34
Joined: Tue Nov 28, 2017 11:09 pm

Re: Meshing questions

Post by Thanos Kagkalos » Wed Dec 13, 2017 3:35 pm

Thank u Thomas.
Ya i just wanted to know that i am on the right track in terms of numbers so i dont do unnecessary additions in polygons or particle count. The values u describe are kinda the default from the plugin and the manual and i wanted to stay near those. But i had noise with those so i had to do huge smoothing to avoid that, couldnt find another way. In my next scene i ll try post the file here to get a more precise approach, if its not a problem :) Thanks a lot!

Thomas Schlick
Posts: 178
Joined: Tue Aug 29, 2017 12:35 pm

Re: Meshing questions

Post by Thomas Schlick » Thu Dec 14, 2017 9:03 am

No problem to share your files here.

The noise you're describing sounds like a scattering effect to me. When you have lots of droplets, bubbles, and turbulence then the light will be scattered in many different directions. And the entire situation changes quickly, because there's a lot of motion in the fluid. This is actually the reason why heavy smoothing reduces the flicker.

Thanos Kagkalos
Posts: 34
Joined: Tue Nov 28, 2017 11:09 pm

Re: Meshing questions

Post by Thanos Kagkalos » Thu Dec 14, 2017 8:59 pm

Sorry for bothering u again, how do i stitch my alembic files into 1 alembic? thanks

Thomas Schlick
Posts: 178
Joined: Tue Aug 29, 2017 12:35 pm

Re: Meshing questions

Post by Thomas Schlick » Fri Dec 15, 2017 8:15 am

Sorry for bothering u again
No worries. Currently there's no method of stitiching Alembics from RF|C4D. It's a planned feature and we have it RF standalone, but not in the plugin right now. We didn't consider this to be an issue, because only the plugin's own tools (mesher, fluid container etc.) provide access to all information like velocity etc. Anyway, it seems as if there's a demand for a stitcher.

Thanos Kagkalos
Posts: 34
Joined: Tue Nov 28, 2017 11:09 pm

Re: Meshing questions

Post by Thanos Kagkalos » Fri Dec 15, 2017 8:16 pm

Thank u, would be useful. I found a way meanwhile, i just export the scene with the mesher on as alembic and is ok, in case anyone is interested.

Thomas Schlick
Posts: 178
Joined: Tue Aug 29, 2017 12:35 pm

Re: Meshing questions

Post by Thomas Schlick » Sat Dec 16, 2017 8:50 am

Great tip! Thanks for that.

Zoran Marjanovic
Posts: 1
Joined: Tue Jan 16, 2018 12:15 pm

Re: Meshing questions

Post by Zoran Marjanovic » Tue Jan 16, 2018 12:22 pm

Hi guys,

There is a stitching tool in RealFlow standalone but it does not work properly. For years now!
I am trying to stitch 1000 cloth/elastic .abc files to one and RealFlow crashes all the time. I run the latest version of RealFlow 10.1.2.0162.
This is soo annoying that Nextlimit developer can´t fix it for now years.

Thomas Schlick
Posts: 178
Joined: Tue Aug 29, 2017 12:35 pm

Re: Meshing questions

Post by Thomas Schlick » Wed Jan 17, 2018 10:34 am

Thanks for raising this issue again and pushing us. You're right, it's definitely something that should have been fixed already.

Anyway, a few notes on that:
The stitcher's code is not from Next Limit, but the Alembic guys themselves.
The reason for these crashes seems to be the Ogawa codec, and the problem is that not all systems are affected. Here on my machine I'm able to stitch around 550 Ogawa Alembics, with 600 and more RF crashes. On the Mac even 1000 files can be stitched without problems, and some other computers in our office can stitch the files as well.

One workaround is to use HDF5 for now. Export will be slightly slower, but stitching can be really slow. In my tests I had 1000 files with 10 MB each and it took some 15 mins to write the final file. But RF didn't crash at least. Could you please give this workaround a try and let us know if it worked?

You can toggle between HDF5 and Ogawa under File > Preferences > Export > Alembic back-end

We're working on a fix right now and hope to have this sorted out soon. Apologies for any inconvenience you had so far!

Cheers,
Thomas

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