The ships' behaviour at sea
 

Hello,

There is something I would like A LOT to improve : the ships' behaviour at sea. They move too much, they look like plastic toys ! I've tried to change parameters in ship.sim file but without result. For example, I changed the mass, gc height, LR and UD (drag).

Does anyone have a solution to correct this problem ? That would be GREAT !

PS : I don't know what means the threads' prefixes.

Look for THOMSEN PARAMETERS APP by Stiebler, it fixes the "rubber duck" like actions of the ships.

From the readme...

"THOMSEN PARAMETERS APP searches through your SH3 'Sea' folder looking for ship.sim files (eg 'NKC3.sim'). It then replaces optionally any or all of eng_power, rudder-drag, surfaced left-right drag coefficient ('LR') and gc_height (= centre of gravity) with values specified by the user. Every .sim file in your sea folder will be examined and altered!"

:salute:

Fahnenbohn,

probably you noticed, e.g., Le Fantasque is less prone to shaky movements than many stock ships. The reason is that its submerged draught (obj_Hydr -> Submerged ->) is set rather deep.

You may wonder what effect the submerged draught may have on surface ships? As far as I understand, the game engine calculates the vertical position basically according to the standard draught but under unruly conditions (especially when the vessel dives into between waves) it becomes partly submerged. Then the submerged draught comes into play.
The standard SH3 setting for submerged draught is 0 of many vessels (meaning, it es equal to the surface draught); that limits partial submersion. Result: the vessel tends to act as a rubber duck. Small vessels (with shallow draught) are especially sensitive to that.
In short: allowing the vessel to dive a bit helps to make it act a bit more natural.

Thanks, the_frog. That's very interesting. I never understood what the Submerged Draft parameter did.

I just spot -checked more that a dozen ship classes, though, and all of them had a value for Submerged Draft which was significantly greater than Surface Draft. That is the case for all ships in NYGM and all ships in MFM 3.2. Seems like another good reason to play NYGM.:)

BigWalleye,

also GWX and LSH use the submerged draught to reduce the ships' movements (at least a number of ships have values different from those of stock SH3). I guess, it has been figured out early. Sadly, I cannot tell who gave me the hint to the submerged draught (likely Rowi58 or "the-modder-once-known-as-privateer").

First, thank you for your replies guys, it's always a pleasure to find help on this great forum !

@ HW3
Yes, I've already tried this, but I've not been satisfied of it at all.

@ The Frog
No, I didn't notice a difference with your new destroyer. But your answer helped me to find the solution ! Indeed, I thought that submerged displacement and draught concerned only submarines. As soon as I read your explanation, I immediately realized that I was wrong and thought to myself : Eureka ! That's it ! I immediately specify a submerged displacement. And that do the trick !

Then, I tested different solutions, and my conclusions :
- the surfaced displacement must be inferior to the submerged displacement, otherwise, the hull is sinking in the water.
- to delete completely shaky movements, the submerged draught must be setted to zero.

The values for your destroyer that are OK for me yet :

http://nsm08.casimages.com/img/2015/...9012952608.png

I've tested the ship's behaviour also with rough weather, and it seems to go well. I don't remember the original values of your destroyer, could you send them to me please ?

F.

I just do a visual adjustment.
:D
http://i108.photobucket.com/albums/n...f.jpg~original

I was modding the ships' physics in SH4 a little while ago. This may or may not apply to SH3:

The LR (left-right) drag only affect turning. The UD (up-down) drag is for pitching.

I generally increased mass of merchant ships, assuming them to be heavily loaded.

Ship stability:

If you want to increase the extent of roll increase the gc height, if you want to decrease the roll, decrease the gc height. However, if you like the extent of roll, but want to make it slower, increase the draft slightly (the surface draft). Sometimes a very small change here will improve the stability a lot.

I had started out trying to manipulate the submerged draft of the surface ships, but ended up setting all of them to zero. The reason is that I found, if the submerged draft is not deep enough, the ships do not sink by flooding. That is, when torpedoed, they would settle down some, then sit there, impervious to flooding. Not good.

I had to do the ships stability mostly by trial and error, not having a mathematical guideline for this. It was tedious, to say the least.

Adjusting just the sim file don't help much on how a Unit sinks.
It's only a part of the file system.
The zon file controls flooding and how a Unit will sink.
You can adjust the sim till the Cows come home and still not see the milk.

To search for information posted by privateer? Search for Madox58.

I never said I adjusted it to help a ship sink. However, making ill-considered changes can interfere with them sinking. If, for example, a ship with a surface draft of 4.0 m is given a submerged draft of 5.0 m, when torpedoed, it will flood down to 5.0 m and sit there, absorbing great blows and floating all the while.

Better to set the submerged draft of the ships to 0, and let the game do it in it's own way.

I must say that I have never seen the behavior you describe. Every ship class in NYGM and every ship class in MFM 3.2 has a Submerged Draft value substantially greater than its Surface Draft value. Other posters say that GWX3 ship classes all have a nonzero Submerged Draft value. I haven't checked them all personally (126 classes for MFM 3.2!), but AFAIK, they all sink. Sometimes it may take an hour or more, just like the eyewitness accounts describe. But they sink. I've never had one get "stuck." I suspect that the 2 supermods (and probably LSH3 and WAC as well) change other parameters to get what each mod's developers consider is a "proper" sink rate. You are most likely correct that changing zero Submerged Draft values in stock SH3 could lead to some funny behavior. There are a lot of complex interactions in the model, and varying just one could cause other problems. The supermod teams have spent a lot of time on issues like plausible sink rates, and a quick-fix solution to one problem can result in unexpected consequences. It is probably more productive to find a supermod that fits your gaming style and accept the ship class parameters pretty much intact, rather than trying to roll your own.

For me, the best solution is to set a value for the submerged displacement (cf post 6 of this thread). If you don't have Le Fantasque destroyer (you are missing something great !), then you can try with Bismark :

http://nsm08.casimages.com/img/2015/...9012953736.png

The result is perfect ! :arrgh!:

Neither did I, until I made the sub. draft changes.

Of course, any mod that's been used for a while will not have this problem; if it did, it would have been corrected already.

There was no problem, as long as the sub. draft was high enough. It is just much easier, imo, to set them at 0, rather than play around with them to see exactly what they should or could be. I never bothered to try to determine exactly how high they needed to be to avoid the issue.

Haven't you ever noticed that a sinking ship will slowly settle, hanging on, until, at a certain point it "let's go", and sinks? Well, if the submerged draft is too shallow, it will not "let go". The game has some criteria, so it knows when a ship is a sunken vessel.

Since every megamod and MFM already has Submerged Draft values tailored to each ship class, why is there a need to "play around" with them? What are you working on?

You may think that existing mods have perfected ship physics, but Fahnenbohn didn't seem to think so, and I was merely trying to save him a little time and effort.

As far as working on a SH3 mod, I'm not. I learned some things that were not generally known about the game physics from working on SH4, and thought maybe some of it might be useful for Fahnenbohn. If nobody is interested, I'll drop the matter.