whitewater issue

   7143   7   1
User Avatar
Member
97 posts
Joined: Nov. 2017
Offline
Hey there,

I recently got some whitewater issues with my FLIP simulation. I attached two pictures; I like the first one but I'am unsatisfied with the second.
As you can see the white water is just some white spheres stretched apart; is there a way to control this and make it look more real?
I already decreased the particle separation of the white water source to 0.025 and added motion blur, but no (visual) difference for the white water except longer render times.

So are there some clues to fix and manipulate this behaviour?

Thanks in advance

Attachments:
good.jpg (1.4 MB)
bad.jpg (1.5 MB)

User Avatar
Member
97 posts
Joined: Nov. 2017
Offline
I'm still engaged in this issue and seeking help.
I increased substeps of the whitewater spray sim to 3 and also increased the impulse count too, to get more particles to fill the gaps. But as you can see, there are still gaps in the spr
Attachment Not Found

ay render that cant be ignored.

So before going beyond 3 substeps I'm looking for other solutions here.

Additional there is a strange cut in the spray particles, and I don't know where its coming from; as the fluidtank and the corresponding whitewater shouldn't hit the boundary.

Attachments:
better.jpg (1.6 MB)
ok1.jpg (277.4 KB)
gaps.jpg (414.7 KB)
boundary.jpg (230.0 KB)

User Avatar
Member
69 posts
Joined: Nov. 2016
Offline
Maybe if you can share your file here with an equivalent proxy geometry for us to check the problem?

Funnily enough, I do encounter the clipping issue of white water in my early attempts but somehow the problem went away I redid it from scratch.

Out of curiosity, any reason for using Impulse Count instead of Const Birth Rate? Here's my settings that I use for a recent ocean splash shot for the spray emission only (I have a separate spray and foam/bubbles emission).

Attachments:
spraysettings.PNG (31.1 KB)

User Avatar
Member
97 posts
Joined: Nov. 2017
Offline
thanks for the Reply. thought I could control the particle amount better with the Impulse Count; just set it back to const. birth rate and it made no difference (same error), so I dont know what Advantages or drawbacks this Option has.

I attached the hipfile, but how can I include the model in the hipfile or provide Proxy geometry without uploading tons of data?
Edited by SiRpRoHxO - Feb. 26, 2018 17:26:42

Attachments:
tie_fighter_flip.hip (4.7 MB)

User Avatar
Member
69 posts
Joined: Nov. 2016
Offline
Your scene file is rather heavy for my PC to handle so I decided to create a demo file with the default sim settings using the Ocean Flat Tank and Whitewater shelf tools.

I only change the size of the tank and left everything at default.

Impulse Count generate particles at every frame which can be useful in some scenario. Anyway do try out a basic scene to see if you can reproduce the whitewater issue.

Attachments:
whitewater_demo.hip (2.8 MB)
whitewater_demo_flipbook.mp4 (1.2 MB)

User Avatar
Member
97 posts
Joined: Nov. 2017
Offline
Hey first i want to thank you for the example file, it helped me quite a lot indeed.

second i've to apologize for my late reply; i've been busy and there was no time for houdini, but fortunately this time is gone, so get prepared for some more silly questions in the forum^^

I noticed that you used a vdb for the spray. I transferred this workflow to my own setup and used the vdb for the spray and the particles for bubbles and foam. This seemed to work for me. The example from the houdini ocean masterclass didn't used vdbs for whitewater and I wondered why as your vdb-example worked pretty good.

So whats the difference respectively advantage for using vdbs for whitewater?
User Avatar
Member
69 posts
Joined: Nov. 2016
Offline
The funny thing is I did watch the H16 Ocean Masterclass video but my brain must have just *click default Ocean Flat Tank shelf tool* *click click more parameters* *click Whitewater shelf tool* and that's how I roll for my practice shots.


The VDB is part of the Whitewater shelf tool if you're referring to the above screenshot.

The VDB setup works together with Volume Rasterize Particles for rendering the whitewater and you'll find this in the Attrib Wrangle:

// Post-simulation tweaks
@pscale *= 1;
@v *= 1;

You can adjust the @pscale value to be smaller than 1 for more finer looking whitewater while the @v controls the amount of motion blur.
Edited by huey_yeng - March 10, 2018 11:38:59

Attachments:
whitewater_vdb_rasterizer.PNG (41.5 KB)

User Avatar
Member
97 posts
Joined: Nov. 2017
Offline
ok thanks for clarifying.

In this case I wonder why they did not use it in the ocean masterclass

But anyway; I think, i'll stay to vdbs in future projects
  • Quick Links