another VDB dilemma

[chishbak]

Hi all,

 

be gently, i'm green

 

So,  i'm working on an old cliche: boat splash in waves:).

 My particles sim is not a big one ( 4 milions ) but  still the VDB is not following the  particle  shape as desired. Anyway , i can live with the quality of the splash , but I'm not happy at all with the quality

of the surface of the ocean .Have this orange skin  texture, like cellulitis ....

I've tried with dilate/smooth/erode -  and this method affects the splash too much loosing it's details ( and i don't want that) and apparently didn't influence de surface of the water ("ocean") enough to 

smooth  the "orange skin" out !!! . I've also tried to decrease the particle separation ( now is .06  to .04 ) : the details pop up of course , but so does the jitter  from the ocean surface ( "orange skin"

 

( i have  an splash tank  and it's copying  an ocean wave surface)

 

attached you have  screens shots with and without VDB operators to see the difference 

 

 

question  

1- what can i do ( what other combination of VDB operators can i use ) to get my water surface   smoother without affecting the details of the splash too much 

Edited February 19, 2015 by chishbak

[chishbak]

here's another  screen  - see the difference between the ocean wave surface  and the VDB surface from the splash tank. - the shape of the waves is the same, behaves the same etc.  ( i have a blend between the two on the edges)

but the details from the VDB surf are far too graini

 

Edited February 19, 2015 by chishbak

[pbarua]

Increase Influence Scale. That should help.

[chishbak]

Thx. For now this could be a solution, but still... i'm loosing the  droplets from the splash.

 

So this solution  should be a compromise between smoothness of the surface and  lack of detail in the splash ?

Or there is another solution out there to keep the  separated particles from the splash (droplets) and also smooth the surface build between all particles - ?

 

maybe just separate the splash from the rest of flip tank   and simulate it different from the body of water?

[pbarua]

Make simulation bit more highres to get more splash so you can get smoother mesh out of that.

Alternatively you can try pointreplicate sop. Play with Points per Point, Uniform Scale, Velocity Stretch, Seed and Radial Velocity. It's bit funky but sometimes true lifesaver. 

[chishbak]

Thx. Sounds good. I'll try with pointreplicate

[lukeiamyourfather]

Make simulation bit more highres to get more splash so you can get smoother mesh out of that.

 

Yes, the simulation looks relatively low resolution. With more detail in the simulation it will be easier to get a smoother mesh while retaining the sharpness and detail in the splashes.

[Juraj]

Also you can smooth your VDB based on particles velocity. So that slowly moving surface will be smooth while splashes will remain detailed.

Here is example: 

[Scratch]

Increasing the influence scale definitely helps, but tends to also reduce overall detail. Balance is key here...

 

The velocity smooth method is great! Tested it myself, works fine for certain conditions (calm ocean vs splash) as in the video. I wasn't able to smooth overall fast moving fluids this way though.

 

Also check this out, I had similar problems

http://forums.odforce.net/topic/21645-vdb-fluid-meshing-smooth-workflow-with-vdb-masks/

 

Convert your particles to vdb using annother particle fluid mesh, smooth it and erode it a bit so the droplets stick out of your new sdf volume. Then use this volume as mask for the smooth VDB (SDF). eveything inside the volume (the body) gets smoothed, everything outside does ot (the droplets). It needs some fiddeling around but one can get decent results!

Edited February 19, 2015 by Scratch

[chishbak]

Great. thx guys. 

Apparently  the smooth velocity does the trick for me ( relatively slow ocean and fast splashes)

 

i'll dive into that, hopefully i'll manage to build it. If not, i'll be back

 

Philipp, i've seen your post. Cool idea to smooth everything  until the droplets dissapear and than use it as a mask  . Could be tricky in my case because i have a large ocean swell - big slow waves that deforme the whole volume a lot , and big splash.

i'll see it anyway. sound easyer to build than smooth velocity ( at least for a rookie like me)

Edited February 20, 2015 by chishbak

[cojoMan]

- lower particle separation so you get more resolution out of your sim, but yes, increased sim times.

- the velocity blending approach should work for you

- you can also try to add another level of high frequency ocean spectrum on top of your big waves after meshing that would break the current splotchy look, and this after the velocity based smoothing should look great.