Acceleration model change?

[Emperor Jake]

Has there been a change in the acceleration model for trains since 1.0.4? Because for example, in 1.0.4 a TGV Duplex from the 2cc set travels at 321 km/h on flat tracks, and when I load it with a newer nightly (20926) the train slows to about 289 km/h as if it had less traction or something. All settings are the same such as slope steepness, etc. No matter what configuration I use, I cannot seem to get a (non maglev) train to go above 300 km/h.

Anyone got an idea why this happens?

Thanks,
Jake

BTW, this might have happened after 20493 because I think I noticed the slowdown after upgrading from that nightly.

[Alberth]

Code: Select all

Commit by terkhen :: r20303 /trunk/src (ground_vehicle.cpp table/engines.h) (2010-08-02 14:54:47 UTC)
-Feature: [NewGRF] Air drag property support for trains and road vehicles. Air drag for vehicles with air drag not set or set to zero will use a default value depending on their max speed.

is probably the cause.

(with thanks to Terkhen for helping finding the change.)

[belugas]

Yup yup yup
Adding realism is not always a good thing!

Buwhahahaha!!!!!

[SirkoZ]

Indeed.

[Emperor Jake]

Yes, that's probably it. Belugas is right

Is there a way to turn this off? It's very annoying to have my 300 km/h trains not using their full potential.

Thanks,
Jake

[PikkaBird]

Get the 2CC guys to fix their vehicle stats? BTW, if it can't reach its posted top speed, then it is using its full potential.

[michael blunck]

And again, here´s the usual contradiction:

Adding realism is not always a good thing!

Belugas is right

It's very annoying to have my 300 km/h trains not using their full potential.

regards
Michael

[Kogut]

And again, here´s the usual contradiction:

Adding realism is not always a good thing!

Belugas is right

It's very annoying to have my 300 km/h trains not using their full potential.

regards
Michael

Maybe I am wrong but I see no contradiction - Beludas said that in general realism is not always a good thing, Emperor Jake agreed with him and later said about one annoying (for him) problem caused by doing sth realistic (or rather unifing sth with TTDpatch: http://www.tt-forums.net/viewtopic.php? ... t=too+fast ).

[michael blunck]

Maybe I am wrong but I see no contradiction - Beludas said that in general realism is not always a good thing, Emperor Jake agreed with him and later said about one annoying (for him) problem caused by doing sth realistic [..].

Nah, read again. In his second quoted post he clearly demands "realism":

It's very annoying to have my 300 km/h trains not using their full potential.

qed

regards
Michael

[Dwight_K._Schrute]

Am I wrong or is there an advanced setting for this???

So if you don't want it realistic..then DO NOT choose "realistic"

I think that is really simple and everyone is happy

[Terkhen]

As already mentioned, you can choose to use the original acceleration model instead of the realistic model. Since that model has never been changed, all NewGRFs prepared to work with it should always work correctly.

The change in r20303 merely adds support for a NewGRF property (see http://wiki.ttdpatch.net/tiki-index.php ... ir_drag_20_). Since the default value seems to be too high for some 2cc trains, it is just a matter of adding appropiate air drag values to the faster trains. Since the realistic acceleration model is likely to change again soon, I'd recommend to wait until then for any tweaks in train/road vehicle stats.

[XeryusTC]

Maybe I am wrong but I see no contradiction - Belugas said that in general realism is not always a good thing, Emperor Jake agreed with him and later said about one annoying (for him) problem caused by doing sth realistic [..].

Nah, read again. In his second quoted post he clearly demands "realism":

It's very annoying to have my 300 km/h trains not using their full potential.

qed

regards
Michael

I think that in his second post he is referring to the fact that his trains are NOT able to reach full speed because of the more realistic air drag implementation. It is actually this realistic drag implementation he wants to turn off so his trains are able to go faster.

[Elukka]

How is air drag different from simply giving vehicles a lower top speed? I'm guessing the max speed on many trainsets already takes it into account.

[planetmaker]

How is air drag different from simply giving vehicles a lower top speed? I'm guessing the max speed on many trainsets already takes it into account.

It impacts on the acceleration.

[michael blunck]

Maybe I am wrong but I see no contradiction - Belugas said that in general realism is not always a good thing, Emperor Jake agreed with him and later said about one annoying (for him) problem caused by doing sth realistic [..].

Nah, read again. In his second quoted post he clearly demands "realism":

It's very annoying to have my 300 km/h trains not using their full potential.

qed

I think that in his second post he is referring to the fact that his trains are NOT able to reach full speed because of the more realistic air drag implementation. It is actually this realistic drag implementation he wants to turn off so his trains are able to go faster.

Well, yes! Funny. Does nobody see the irony here? He´s complaining about the fact that introduction of a more "realistic" feature (air drag) prevents him from playing in a "realistic" way, i.e. "to have my 300 km/h trains not using their full potential".

It has been already stated that the source of the problem is a flaw in the used vehicle set (not specifiying a factor for "air drag"), but not in the way "realistic" kinematics is set up in the game. Many other sets already included appropriate "air drag" factors since years, which hadn´t been used by OTTD until recently. These sets should all work OK.

How is air drag different from simply giving vehicles a lower top speed? I'm guessing the max speed on many trainsets already takes it into account.

"Air drag" is a force increasing quadratically with speed. Hence it´s important to include it for fast vehicles and/or for very weak ones:

F_net = TE - c0 · W - c1 · W · v - c2 · v² - F_incl

[F_net = net force, TE = actual tractive effort, W = total weight of train, v = speed, c0 = coefficient of static/kinetic friction, c1 = coefficient of rolling friction, c2 = coefficient of air resistance, F_incl = tangential forces of inclined track]

regards
Michael

[Alberth]

Well, yes! Funny. Does nobody see the irony here? He´s complaining about the fact that introduction of a more "realistic" feature (air drag) prevents him from playing in a "realistic" way, i.e. "to have my 300 km/h trains not using their full potential".

Certainly, I find it always fun to watch how fast people drop 'realism' as goal whenever it is does not fit in their line of reasoning

[Terkhen]

Since the introduction of realistic acceleration for road vehicles, they have been sharing their acceleration behaviour with trains. As a result of using the old air drag method for trains, some standard road vehicles were unable to reach even 70% of their top speed. The introduction of the new air drag method in r20303 fixed this problem, but it increases the impact of air drag in long and/or fast trains.

The solution to this issue is adding a corrected air drag value for those vehicles that don't work as intended with the default value. The changes to realistic acceleration I mentioned in my last post have been commited in r21106, so now is a good moment for testing and tweaking train and road vehicle NewGRFs.

[Elukka]

...Well, I had no idea the acceleration model was that complex. I guess it's a good addition, though I'm not sure how well it'll work with existing trainsets.

[michael blunck]

...Well, I had no idea the acceleration model was that complex. I guess it's a good addition, though I'm not sure how well it'll work with existing trainsets.

Every train set initially developed for TTDPatch (CanSet, CSD set, DBXL, Dutch train set, Japan Set, NARS, Serbian set, Swedish trains, UKRS, US set, ...) should work OK, simply because that particular feature had always (> 5 years) been used there.

regards
Michael

[AndersI]

Every train set initially developed for TTDPatch (... Swedish trains ...) should work OK, simply because that particular feature had always (> 5 years) been used there.

Although I must confess that I haven't really looked much at the performance of my trains, they are really still very much a WIP. It's quite possible that some of them don't reach their advertised speeds - especially as I almost always play with "wagon speeds" on, which means the trains will not be allowed to reach their top speed anyway.