PFD Toolbar: Ocean adjusts scale to match 25m

[joshclos]

When using the Phoenix FD toolbar to "Setup ocean simulation for selected objects," I have found that it will change the scale parameter in the dynamics section of the liquid container based on the size of the object selected when you initiate it. It seems to adjust the scale to a 25-meter size, so if you create an ocean using box geometry that is 10x10 meters, it sets the scale to 2.5 and if you create it with a box of 50x50m, it sets the scale to 0.5 (and 1.0 if the box is 25x25m). It seems strange that it would change this parameter since real world scale is always the goal in simulations and even the documentation suggests that it should remain 1.0 as often as possible.

I recently set up a sim without realizing the change and spent a couple hours adjusting values before noticing my scale of 0.09. It's my fault for not noticing in the first place but I thought I would share this as a cautionary tale.

Josh Clos

[georgi.zhekov]

We implemented this as a secure method that will ensure you will get good results no matter what object you will use. The presets are meant to be just a starting point and you can tweak the sim according to your needs after that.

[baro]

Hey Josh,

thanks for pointing this out. I've spent weeks trying to figure out a pattern/ratio/relationship between units/grid sell size and foam/splash settings. I wasn't very successful and my fiddling with settings often made results worse. what was your experience? what did you change the scale to and how the results turned up?

cheers
pl

[baro]

would be so nice if someone updates the ship video tutorial showing the new workflow - preset as a starting point and going trough all the tweaks necessary to get good results. doesn't even need to be video. a written tutorial would do.

cheers
pl

[joshclos]

Yes, that's right that presets are starting points but scale is the most important setting. Since PhoenixFD is a physical simulation tool it's simply odd that its presets disobey the #1 rule of simulation (keep proper scale). In cases such as mine, that method is unable to give good results since my initial object was unusually large. It seemed like a tiny stream instead of a large river.

It won't prevent me from using Phoenix of course and I'm still really enjoying it. I just wanted to share my findings in case someone came across a similar problem.

[joshclos]

Baro,

Regarding your previous post - I don't think there's a pattern of settings you'll find but if you keep the scale to 1.0 as a rule, many of PhoenixFD's default settings are really well suited for most types of water. As for grid cell size in general, the higher the better. But you will find it easier on your patience to set up sims at a larger cell size (low resolution) and increase it later when you're prepared to let it calculate for hours at a time. In my case, I just changed the scale back to 1.0 and at that point the entire sim changed so I had to go back to tweaking settings from step 1 but I got the sim to look as I wanted.

[joshclos]

Baro,

Regarding the ship tutorial - I'm sure you could still follow that tutorial using the new version 3 of Phoenix if that's what you meant by the "new workflow." Most of that tutorial still applies and any new settings you notice will be in the documentation. I just wouldn't recommend starting with the toolbar tools - just make the fluid container manually and it won't have the scale adjustment.