Exhausted

[Killer Wolf]

right, need help re exhaust drawing please.

new ship is 142m long. i wanted 2 overlapping exhausts, one wide and short, the other long and slim. again, i measured my exhaust port in MilkShape and again when the exhaust is drawn the width is wider than i want : all other measurements i take (eg, views and laser placings etc) work out fine. any thoughts as to why this might be?

2ndly, how does the exhaust length work? i've knocked the value back down to as little as 10 and it's still almost the length of my ship when i'm at full burn : how come the shipdata info doesn't constrain it?

cheers.....

[JensAyton]

As it stands, all exhaust plumes are the same length (at a given thrust level).

[Smivs]

right, need help re exhaust drawing please.

new ship is 142m long. i wanted 2 overlapping exhausts, one wide and short, the other long and slim. again, i measured my exhaust port in MilkShape and again when the exhaust is drawn the width is wider than i want : all other measurements i take (eg, views and laser placings etc) work out fine. any thoughts as to why this might be?

2ndly, how does the exhaust length work? i've knocked the value back down to as little as 10 and it's still almost the length of my ship when i'm at full burn : how come the shipdata info doesn't constrain it?

cheers.....

Hi KW,
In shipdata there are six number specifiers for the exhaust flumes.
For the Mk III Cobra it looks like

Code: Select all

exhaust = 
("-19 0.0 -32.5 15.0 7.5 12.5",
 "19 0.0 -32.5 15.0 7.5 12.5");

as there are two exhausts.

the first three numbers control the positioning (x,y,z axes) which in English means (relating to the centre point of the ship) left or right, up and down, back and front.
The last three control the size.
The first is the width of the flume, the second is the height and the third the length.
There does seem to be a maximum length...I hit this doing the exhaust for that 1.5 Km liner I'm working on...but I don't think there is a minimum.


My new YellOo Cab has a wide exhaust to suit the 'thruster' and looks like this

Code: Select all

exhaust =
		(
			"0.0 0.2 -25.0 5.0 2.0 9.0",
		);

where the width is 5.0 and the height is 2.0. The liner has a length of 150! and that still looks tiny on a 1.5Km ship.

maybe try something like

Code: Select all

x.x y.y z.z 10.0 10.0 0.5

which should give a medium size round exhaust which is really short.

I've just spotted Ahruman's post...I think what I'm describing is the 'cruising speed' appearance.

[Killer Wolf]

As it stands, all exhaust plumes are the same length (at a given thrust level).

so what exactly is the point of the length attribute then? it doesn't seem to constrain a plume to its length, and its length doesn't seem accurately represented. how does the game engine actually use this value?

[Commander McLane]

As it stands, all exhaust plumes are the same length (at a given thrust level).

so what exactly is the point of the length attribute then?

It has no point, it is completely ignored. Exhaust length depends only on the current speed of the ship (the faster, the longer).

You could file a bug report and see if one of the developers is willing to fix it.

[Smivs]

So all those subtle tweaks I've made to exhaust lengths have done precisely nothing? Great

[JensAyton]

so what exactly is the point of the length attribute then? it doesn't seem to constrain a plume to its length, and its length doesn't seem accurately represented. how does the game engine actually use this value?

It doesn’t, ever since the dynamic, bendy exhaust plumes were introduced (1.55).

[Killer Wolf]

As it stands, all exhaust plumes are the same length (at a given thrust level).

so what exactly is the point of the length attribute then?

It has no point, it is completely ignored. Exhaust length depends only on the current speed of the ship (the faster, the longer).

You could file a bug report and see if one of the developers is willing to fix it.

is it a bug, d'you think, or should i just post it in the suggestions page?
i think it would be good to define the length, i have plans for a bulk hauler that would have big long-plumed engines and the back and smaller short-plumed ones at the sides, i'm sure others would be able to take advantage of the change too.

[Commander McLane]

is it a bug, d'you think, or should i just post it in the suggestions page?
i think it would be good to define the length, i have plans for a bulk hauler that would have big long-plumed engines and the back and smaller short-plumed ones at the sides, i'm sure others would be able to take advantage of the change too.

As per Ahruman's explanation

It doesn’t, ever since the dynamic, bendy exhaust plumes were introduced (1.55).

it's a feature, which exists since Oolite 1.55. I haven't played any version before that, so I don't know what the exhaust plumes looked like before. My guess is that you could define a fixed height, width, and length for them, and they would always have that shape, even if the ship stopped (perhaps not when stopped, but at least at a very slow speed). The plume would also not bend when pitching.

Obviously this seemed unsatisfactory. Therefore the exhaust plumes were made dynamic. You only define height and width, and the length only depends on the ship's speed. Full stop: no plume. Slow speed: short plume. High speed: long plume. This makes sense somehow, because you would expect the engines to put out more exhaust when the ship flies faster.

For your plan that means that a big engine at the rear of the ship and a small engine at the side, when working in the same way, pushing the ship to a certain speed, would produce the same amount of exhaust, therefore the plume will be of the same length.

What you could suggest, however, is making the length also depending on height and width, or the diameter of the plume. One could argue that a very wide plume would get longer at the same speed than a very narrow plume. This would allow for some variation.

[JensAyton]

is it a bug, d'you think, or should i just post it in the suggestions page?

Given that the majority of OXP ships postdate 1.55, “fixing” this would mean all existing exhaust plumes would get random, unintended lengths. An actual fix would involve either adding a new property (changing the syntax of exhaust plume definitions), or providing a sensible behaviour like making it proportional to the cross-section of the plume, perhaps with some absolute speed factor thrown in.

Neither approach is impossible, it’s just that we want a feature freeze soon so we can go to beta.

(If anyone does file anything, the need to do it a new way makes it a feature request, not a bug report.)

[Killer Wolf]

well, i've changed my current ship so it's not important. i thought that all ships currently would have the exhaust length variable so the code would just make it that that length was reached at full burn and the speed % below that would be a % of the plume length.
still, no worries.