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FLIP Fluids H12.5 vs H13


borisb2

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Hi.

 

Coming from naiad and synapse (weta) I am finally starting to use houdini for water. Unfortunately I started with H12.5 and are now trying to adapt my setups to H13. What looked more natural in H12.5 now looks a lot more stringy/tendrily in 13. Is that a common issue? Sure, when I just open a H12.5 scene in 13 and resim it looks similar - but starting a new scene and using exactly the saem values for source / flipObject / flipSolver, the fluid looks A LOT different .. hmmm

 

Have a look here:

About 5mil particles

23mil voxel count (.007 particle separation) 12x5x5m fluid

 

Houdini 12.5

riverbed_12_0069.jpg

 

H13

riverbed_13_0069.jpg

a lot more tendrils/clumping

 

flipbook:

www.ambientfx.de/files/riverbed_125.mov

www.ambientfx.de/files/riverbed_13a.mov

 

So I guess there are different settings in the subnets that would need to be matched .. which is close to impossible of course?

 

Any advise what I could improve here?

 

Thanks a lot

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Here's another attempt to get similar look.

 

Left: the cache from Houdini 12.5

Right: same setup (started in a new scene), using EXACTLY the same settings for fluid-source, Flip object, collision and Flip solver

 

The fluid from H13 looks AWEFUL! ... What's going on here?

 

flip_comp2.jpg

Edited by borisb2
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If you could attach both scenes it would make it easier to assess what the difference is.

 

You could just methodically go through all the settings and see if any of the defaults have changed, my first guess would be maybe something in the reseeding.

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some options are missing h12.5 compare to h13, they can look same but resault is diffrent

 

Try to turn off automatic extrapolation by default - solver tab on flipsolver, but when you open 12.5 in h13 auto extraplotion is on by default.

 

chk image and video, 12.5 and h13 with extraplotion off look similar

 

 

 

post-2996-0-86948600-1411385505_thumb.jp

flipCompare.mov

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Also, when comparing to H12.5 sim, I'm still loosing a lot of volume. That must be the reseeding? Even with similar values?

 

flip_comp4.jpg

 

 

Here's my test with disabling the "automatic extrapolation"

flip_comp5.jpg

It's cutting off the front edge... and I also can see the volume loss (feathering out on right edge) .. similar amount of particles and voxels in both sims

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If you could attach both scenes it would make it easier to assess what the difference is.

 

 

I'll just echo eetu.  There were a fair number of changes in FLIP from 12.5 to 13, but obviously simulation quality is always supposed to be improving.  If you can post a simple example we can look at what might have changed.

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.. looks like I overlooked one mismatch in substepping (only at scene level DOP node) .. I was focusing on all values and nodes INSIDE DOPS and totally overlooked the DOP-node itself..

 

still not identical sims but a lot closer..

 

Thanks for your help guys!

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.. looks like I overlooked one mismatch in substepping (only at scene level DOP node) .. I was focusing on all values and nodes INSIDE DOPS and totally overlooked the DOP-node itself..

 

 

Ah, that would make sense.  You have pretty fast-moving water, so the additional substeps would definitely help with the collisions and volume preservation.  Just note that substepping at the DOPnet level is a bit more expensive than at the FLIP solver level.  Some operations like Reseeding occur once per DOPnet solve so it will change the look a bit to go from 2 DOPnet substeps and 2 FLIP substeps to just 1 DOPNet substep and 4 FLIP substeps, for example.  But it should solve a bit quicker.

Edited by johner
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