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[1.8.x-1.10.x] SmokeScreen 2.8.14 - Extended FX plugin (18 April 2020)


sarbian

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This was changed in the most recent version

Ah, I still had the previous version.

The latest smokescreen fixed the dotted particle issue when moving at speed but it did some weird stuff to the flame effects.

I looked at the latest HotRockets! together with the latest SmokeScreen, and I fail to see what weirdness you're talking about.

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This begins to talk my language...

r3SkU1H.gif

Only hate when smoke overlay the flame... :P

BTW eggrobin, what is the max value for dragCoefficient and stickiness? Work them without the logarithmicGrowth? With logarithmicGrowth my smoke looks like a lot of "bubbles".

Edited by Proot
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Problem with all this(or with Hotrocket's configs - not sure if the FX plugin directly affects this behaviour or it's the configs that do it) is that the flame of the engines acts as smoke - it follows velocity trajectory, rather than engine emission direction.

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This begins to talk my language...

http://i.imgur.com/r3SkU1H.gif

Only hate when smoke overlay the flame... :P

wasmic is right, the flame should really only be luminous smoke (another MODEL_MULTI_PARTICLE_PERSIST with a .mu using a similar smoke model, but with an additive shader maybe?). You should see the flame for liquid engines, but not for SRBs. Whenever I add a setting for initial velocity offset u.a.r. on a disk you'll be able to force the smoke to engulf the flame completely.

BTW eggrobin, what is the max value for dragCoefficient and stickiness? Work them without the logarithmicGrowth? With logarithmicGrowth my smoke looks like a lot of "bubbles".

The drag coefficient is a drag coefficient, set it as high as you want.

(1 - stickiness) is the proportion of the normal velocity of the smoke that gets turned to tangential velocity on collision, so stickiness should be in [0, 1].

If you experience the "bubbles" problem you should try decreasing the velocity, increasing the stickiness, increasing the drag, increasing the size or increasing the density (with logarithmicGrowth particles don't slow down as fast because they have a lower cross-sectional area, so you need to compensate for that otherwise they fly everywhere).

Fixing the bubbles with exponential growth (the stock 'grow') does not make much sense.

EDIT:

Problem with all this(or with Hotrocket's configs - not sure if the FX plugin directly affects this behaviour or it's the configs that do it) is that the flame of the engines acts as smoke - it follows velocity trajectory, rather than engine emission direction.

I noticed that, that's Nazari1382's doing, but I think that's what actual flames do, it's just that with more conventional trajectories you don't see it.

spacex-grasshopper.png

EDIT: Nope, and nope. See post #133

Edited by eggrobin
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I noticed that, that's Nazari1382's doing, but I think that's what actual flames do, it's just that with more conventional trajectories you don't see it.

http://images.gizmag.com/hero/spacex-grasshopper.png

Take a look at a Shuttle launch, the flames mostly move straight out of the engines (engine emmission direction), and not the actual velocity trajectory. The reason the flames look like that on the Grasshopper is because it's not the actual propellant exhaust; it's the exhaust from the turbopump.

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Take a look at a Shuttle launch, the flames mostly move straight out of the engines (engine emmission direction), and not the actual velocity trajectory. The reason the flames look like that on the Grasshopper is because it's not the actual propellant exhaust; it's the exhaust from the turbopump.

You're right, though a STS launch is not a very good example, as the SRB flames are hidden by the smoke and the SSME are hydrolox (invisible flame).

Looking more closely at Grasshopper makes this very obvious though, the engine exhaust goes straight down.

Having tried things out again, it turns out smunisto was right, my dotted smoke fix is at fault. The fix is as follows.

Nazari1382: For all MODEL_MULTI_PARTICLE_PERSIST whose .mu does not simulate world space (e.g. flames), add the following setting to the MODEL_MULTI_PARTICLE_PERSIST block:

fixedEmissions = false

This will make HotRockets! work with the latest version of SmokeScreen.

If the models do not simulate world space they don't need the dotted smoke fix, and the dotted smoke fix is written with world space in mind. fixedEmissions = false disables the fix for that MODEL_MULTI_PARTICLE_PERSIST.

A remark: with the latest SmokeScreen you can probably have realistic turbopump exhaust by using a flame model that simulates world space, setting physical = true and a low initialDensity.

Edited by eggrobin
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That's what happens when I code too late : French start popping up in my code :)

It depends a lot of the effects.

Long lasting smoke/dust effect can slow down the game fast if they overlap ( like if you stay too long on the launchpad )

Strangely collision does not have a big impact on my PC but I have an i7 ...

Moi aussi, mais dans mes reponses. DAMN IT I DID IT AGAIN!

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You're right, though a STS launch is not a very good example, as the SRB flames are hidden by the smoke and the SSME are hydrolox (invisible flame).

Looking more closely at Grasshopper makes this very obvious though, the engine exhaust goes straight down.

Yeah, I could probably have found a better example - the thing with the STS, however, is that if the conditions are right, you can actually see the flame, and then it's obvious that the flames, due to the SSMEs being angled, is parallel to the engines and not to the velocity vector. So in some (admittedly very specific) circumstances, the STS would be a great example. That was my logic when writing the previous post, anyway.

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Ah, I still had the previous version.

I looked at the latest HotRockets! together with the latest SmokeScreen, and I fail to see what weirdness you're talking about.

When you're going very fast, the flame starts to lengthen instead of staying the same size through the whole flight. Try it with a small payload and something like the mainsail. Once you hit a couple hundred m/s the flame is 5 times as long. I noticed it snapped back to the correct size though at a certain altitude but the smoke particle did their separate cloud clumps again.

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When you're going very fast, the flame starts to lengthen instead of staying the same size through the whole flight. Try it with a small payload and something like the mainsail. Once you hit a couple hundred m/s the flame is 5 times as long.

I found the issue; the fix is a cfg edit, see above.

but the smoke particle did their separate cloud clumps again.

This is really interesting. Is at at a specific altitude, or at a specific velocity? If it's the latter I think the issue is that I forgot to take Krakensbane into account.

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The flame is visible:

Nope, the flame isn't visible, or rather, it isn't distinguishable from the superheated smoke. Not even in the end, where the smoke coming right out of the SRB is red-hot but instantly cools to a black smoke.

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You can see the flame perfectly in vertical (look the video again :confused:) but is so hot and fast that, as you say, isn't distinguishable from the superheated smoke, especially in a heavy lift up. But for that we need something more similar to this.

I can't (better: I don't know how) make interact the flame with the smoke. So for the moment that level of realism is not possible for me.

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You can see the flame perfectly in vertical (look the video again :confused:) but is so hot and fast that, as you say, isn't distinguishable from the superheated smoke, especially in a heavy lift up. But for that we need something more similar to this.

I can't (better: I don't know how) make interact the flame with the smoke. So for the moment that level of realism is not possible for me.

You don't need to make the flame interact with the smoke because, as you say, the flame is indistinguishable from superheated smoke; you don't even need the flame. Have you tried making smoke with an additive shader so it looks lit up?

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As far I know that requires work in unity, where I'm a total n00b.

It does, and so am I. Perhaps you can ask Nazari1382 for pointers:

Also if you need pointers on creating a mu let me know

EDIT:

This is really interesting. Is at at a specific altitude, or at a specific velocity? If it's the latter I think the issue is that I forgot to take Krakensbane into account.

Testing has shown that it is indeed velocity, and the switch back to dotted smoke occurs at 750 m/s, so it is Krakensbane. I have opened an issue (#6).

EDIT:

Created a pull request (#7) with a fix for #6.

Edited by eggrobin
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I'm a bit busy IRL so I did not code much those last few days, but eggrobin is doing a great job :)

You can get the dev version with his fix here :

http://ksp.sarbian.com/jenkins/job/SmokeScreen%20Dev/

(I did not have the time to test the build, but they should work fine)

Edit : it looks good Proot !

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Perhaps a change of thinking, if I may interject.

Rather than treating the flame and the smoke as two separate identities, one should look into working on the design as a single unified gas 'particle' changing states.

Consider what the gasses are doing based on the state of the engine in question.

State 1: Low altitude/At Sea Level

A: Freshly burned exhaust gas is in a state of rapid expansion as it exits the nozzle of the engine. This expanding gas is brightly colored (if it's not transparent) and under high pressure, and wants to expand like an explosion.

B: However, as the gas leaves the confinement of the bell, it comes into contact with the atmosphere (free stream), thus, its expansion is limited, and momentum of the gas particles shapes the blast mostly downwards. (The vertical axis)

C: Consider that the air itself is not static around the exhaust cone. Immediately leaving the nozzle, the exhaust gasses interact with atmosphere, dragging it down with it as it moves.

D: Atmosphereic gasses being dragged get sucked into the exhaust stream a few meters down from the exhaust cone, mixing cooler, slower moving gas into the stream and forming a diamond-shaped 'shock' component where the two flow speeds interact. (Resulting in your shock diamonds and/or your spear-shaped flame). This happens at several intervals as the exhaust stream stabilizes at a certain engine flow rate.

E: As exhaust gasses move further away from the nozzle, the drag of the atmosphere saps the vertical component of its velocity, allowing the gas to begin to expand to the sides more rapidly as it cools and mixes further with ambient.

F: By now, you're leaving the 'flame' portion of the exhaust stream as gasses cool below 'glowing' and slow down considerably, expanding in all directions. Vertical direction is more a factor of leftover momentum at this point.

State 2: Velocity increasing

A: The same conditions are present as before, however, the 'length' of the 'flame' portion of the exhaust stream is greater due to the increased speed in which the atmosphere is interacting with the exhaust stream. The shock diamonds are elongated and it takes 'longer' for the atmosphere free-stream to enter the exhaust stream and mix.

State 3: High altitude

A: Watch the Apollo launch videos at a timelapse speed. As altitude climbs and ambient-pressure decreases, the constricting effect of the free-stream drops off, allowing the exhaust cone to widen dramatically to the point where, just moments after leaving the nozzle, it's over five times wider than the rocket itself.

https://www.youtube.com/watch?v=HCsbiZ6z3QE

(2:00: Perfect view of the exhaust stream immediately following launching showing how the free stream gets 'sucked into' the exhaust cone a few meters down)

(3:18: Mid-flight exhaust stream showing the interactions of the flow very clearly)

(3:53: The dramatic difference between the exhaust streams moments after launch and high altitude are clearly visible here.)

EDIT:

https://www.youtube.com/watch?v=d0-DEtKcsjg

(10:40: Good up close view of the exhaust stream.)

Edited by AdmiralTigerclaw
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I'm a bit busy IRL so I did not code much those last few days, but eggrobin is doing a great job :)

You can get the dev version with his fix here :

http://ksp.sarbian.com/jenkins/job/SmokeScreen%20Dev/

(I did not have the time to test the build, but they should work fine)

Edit : it looks good Proot !

I don't know why, but in that version all seems broken for me: the game becomes absolutely unstable and very slow when I try to launch a rocket. Oh, and the most important thing, no smoke at all.

I'm doing something wrong?, is there some change that I don't know?, or maybe are the .mu created for the previous version with a bad behavior now?

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