My ship simulation issues

[jaswane]

Hi. I'm trying to make an animation of one of our real ships called Skandi Aker simulated through water with Phoenix. It is 27 m wide and 156 m long. I have a very detailed 3d model of it, but have choosen to use a dummy hull for the simulation.

I went through the excellent new ship tutorial on youtube yesterday and set up a scene with my hull. I'm quite satisfied with almost everything expect that the particles (green) looks a bit strange. They are flying to high and looks more like smoke than water particles. Its visible in this preview animation. At 0:06 it looks like smoke and just slide along the hull for a long time. I have used the same settings but I guess something is wrong. Do you have any ideas how I can adjust this? The foam are is much narrower on mine than yours, but that might be the shape of the hull. The speed is almost the same, the units are in cm and the vessel is in correct scale.

Here are my settings:

[Ivaylo Katev]

the reason is the air friction (thanks for the all roll outs opened!)
i see your droplet size is 1mm , and your air friction is 100. this produces extremely high air friction and the droplets refuse to fall down. just decrease the air friction or increase the size.
little bit more explanation: we have separate control over the air friction and the size, because the size is directly related to the rendering and beside this the size may affect the simulation when "liquid like" option is used. so, the air friction is used to avoid the size changes.

[jaswane]

Ah. Thanks for the quick reply. That makes perfect sense. Will do a new re-simulation which will be finished tomorrow.

[jaswane]

I have done some more test and I'm like the results, but there are still things I would like to improve. I have attached images of a render, a viewport preview, my current settings and some tests I did to find out for myself which of the rendering methods (bubbles, splash or point) that looks best in this situation. Maye you have some comments here too. The scene is still very similar to your ship tutorial and sample scene with regards to ship size and speed.

What I would like to increase the amount of foam around the bow of the ship and to the sides. In the tutorial the ship makes a very nice and wide section of foam, but in my simulation it's a very narrow foam section along the ship and many particles go underneath the ship. Maybe the reason is the shape of the hull or that I use to few particles, or do you have any other tips for me?



I have also looked at what looks best of bubbles, splash or point. So far point or bubbles looks best, but with bubbles I get some very large bubbles and when I decrease the size they almost disappear. Same settings on both foam and splash on these tests: Size multiplier 1, variation 0, distribution 1, velocity 1 and size limit 0,01m.

Thanks for any comments and help. I learn new stuff all the time.

[Ivaylo Katev]

haha, when we made the ship scene we was trying to make the foam narrow, but you need the opposite case
the foam gets narrow when the ship is moving faster. you can try to decrease the speed and to increase the birth amount. to prevent the underwater foam (why? it may give you excellent result!) you can increase the rise speed. but i recommend you to try to shade it better, instead to remove it. make your water more transparent and this underwater foam may give you very good blue gradient .
about the large bubbles - you can remove them if decrease the size distribution before the simulation, or if you won't simulate again you can use the subgroup+size limit options to disable the rendering of the large bubbles, leaving the small ones with the same size.

[jaswane]

Thanks again. Think I will slow down the ship, make the water a little bit more transparent and leave the rest as is. Looks great from the back:

[Ivaylo Katev]

don't forget to adjust the fake propellers (this box in the sample scene) , otherwise the animation looks like the ship is dragged, not propelled

[jaswane]

Rendered out a few frames here. Couple of things I need to fix and have solved in another simulation like slowing the ship down to get more foam. And I need to adjust the "particle box" at the rear as you said. This is rendered with Point, which is quite slow. I neew to adjust the Bubble shader and use that instead.

[Ivaylo Katev]

i think the rendering performance desires a tutorial, because we met many user scenes with extremely high render times.
our original ship scene renders about 1 min per frame with 5 M particles.

[TSR_trix]

+1 for that!
I havent find a proper way to render foams etc. in point mode with reasonable render times.
I always ended up to render even particle fogs with bubble mode cause its easy to adjust the size and render speed.
But im sure if we could render particles like with krakatoa, it would be awesome.

[jaswane]

Yes tutorial in rendering performance would be great.
To get more speed on the particles from the "fake propeller" box, is it the Discharge I need to increase on the PHXSource? Right now it just looks like particles are forming without any speed which looks weird when the ship is moving as you mentioned earlier. I have a value of 14 on the discharge and you have 70 on your ship sample scene so I guess I need to increase..

[Ivaylo Katev]

yes, the discharge controls the speed of the outgoing water. the best way to find the correct discharge is temporary to disable the initial fill up, the gravity and to run the simulation, this will allow you to see the jet and its speed