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Question D3D11 Implementation: Realistic Re-entry effects and Lens Flare

Cras

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After a good and long chat with asmi last night, he brought up a good point on two issues that are to be implemented at some point.

Plamsa re-entry effects
As many of you I think are aware, the re-entry "flames" as they are implemented in orbiter are not quite in line with what is seen in real life. Case in point, if you re-enter the Space Shuttle with the correct entry profile, you will never see flames. As you all probably have in in pictures and/or video, this is not at all the case. The Shuttle experienced re-entry flames, leaving that distinct trail in the sky, and engulfing the windows on the flight deck with that reddish glow. The Shuttle experienced this at an altitude much higher than you can normally get re-entry effects in Orbiter.

So the issue here is, what is the discrepancy? What is the actual effect seen on the Space Shuttle, how does this differ from what is in Orbiter now, and would it be possible to implement a more advanced/complete simulation of this effect in the D3D11 client, both in regard to the conditions for their appearance, and their appearance in general.

It is also related to this from the Orbiter project sub-forum:
http://www.orbiter-forum.com/project.php?issueid=601



Lens Flare
asmi brought up adding lens flare, which would be tremendous. Anyone who has messed around in Space Engine would appreciate having the sun generate a flare and what that would add to the Orbiter graphical environment. While it is easy enough to explain the constituents and the mechanism in real terms of a lens-flare, we lack the mathematical concept. If anyone could shed light on how to mathematically describe the lens flare, how to generate a realistic looking one with Orbiter's partial concept of the camera view point, that would be tremendously helpful.

-----------

This was initially posted in the main D3D11 dev thread, but it was decided that it is best to have it in its own thread so it doesn't get lost in the other discussions going on in there.
 

boogabooga

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It's wrong on the other end, too. You would never see plasma at Mach 3 just because the dynamic pressure is high.
 

Mandella

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I'm all for reasonable plasma effects, but lens flare?

Correct me if I am wrong, but isn't lens flare an artifact produced by the camera? In other words, a living observer looking at a bright light does not see anything like a "flare," but we have come to expect it from watching movies and seeing pictures that do.

Yep. I just tested that by staring at this overhead lamp. Spots, but no flare.

:eek:wned:
 

Moach

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well, yeah...

lens flare is a camera artifact, namely from imperfections on the lenses themselves...

lenses that do not flare at all have been available since years ago - but many directors will at times choose to go for older, flare-prone lenses in order to exploit the dramatic effect it produces


you see, sometimes, it's not what's "right" that makes something feel more realistic, but really what isn't :rolleyes:
 

Cras

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Speaking as a camera man, I love lens flares. Maybe not as much as J.J. Abrams....no probably just as much as J.J. Abrams.

Some other visual effects are planned, but these are two that more information is required to get them done properly.
 

asmi

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It's wrong on the other end, too. You would never see plasma at Mach 3 just because the dynamic pressure is high.
Well that is why this thread exists in the first place - since neither myself nor Cras nor anyone else I know don't have a clue how to calculate when this effect occurs, and what it's supposed to look like. As I sort of remember from physics lectures in university, plasma is essencially an ionized gas, which makes me think that in order for it to show up, something has to ionize that. Since it can't be magnetic field, it's most likely high temperature and/or high pressure. And here I approach limits of my knowledge of this subject, so I'm asking anyone who knows the subject to assist me in understanding of science here as well as some quantitative description of the process.
 
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Mandella

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Speaking as a camera man, I love lens flares. Maybe not as much as J.J. Abrams....no probably just as much as J.J. Abrams.

:lol:

Come to think of it, there *are* certain sci-fi scenarios that would look wrong without it.

But do include a slider, if at all possible, so we can set the level of the effect ourselves.

As for the plasma trail, although I think I have a basic understanding of it, I'm sure someone far more knowledgeable than me will be here shortly to explain it -- with math!
 

Hielor

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If you add lens flares, please make it possible to turn them off.

with Orbiter, I'm not watching something recorded through a camera that would be prone to lens flares. It's a simulation of sitting in a cockpit, when you wouldn't have lens flares.

Of course, if anyone makes addons from the new star trek movie, lens flares would be required to get the full effect.
 

asmi

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Relax guys, we can certainly make it optional if you insist on that, allthough when I look with my own eyes, for example, on a car's headlights during the night - I do see rays coming out of light... Maybe there is something wrong with my eyes :)
 

n72.75

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Relax guys, we can certainly make it optional if you insist on that, allthough when I look with my own eyes, for example, on a car's headlights during the night - I do see rays coming out of light... Maybe there is something wrong with my eyes :)

Yeah, my eyes have "lens flares" too. Likely it's exposure to dust and dirt scratching the surface of your eye.
 

Xyon

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I have no such lens flares on my eyes, I'm neither here nor there on lens flare as an effect. For film-making, perhaps, it might come in handy, but for other times I'd probably prefer it were turn-off-able.

Proper re-entry plasma, now, I won't ever disagree with. BRING ON THE SUPERHEATED ATMOSPHERE! :D
 

Urwumpe

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The problem is, that you need to know the vessel aerodynamics for proper reentry flames. The Shuttle only has such plasma, because its shape has extreme differences between minimal and maximal local heat flux - on the average, the shuttle is really rather cool.
 

Mandella

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Relax guys, we can certainly make it optional if you insist on that, allthough when I look with my own eyes, for example, on a car's headlights during the night - I do see rays coming out of light... Maybe there is something wrong with my eyes :)

Don't worry, I'm quite relaxed. I really can't get a good case of nerd rage going over photo effects.

:lol:

Continuing the discussion, when I think of lens flare I think not so much of rays, but of circles or rings repeating in a line intersecting the light source. Do you get those when you stare at headlights?

Reading up on the effect, I can see it might be possible, since irregularities in organic eyes *can* result in lens flare effects -- but they manifest differently for different people, of course. And as I said above, all I ever get is spots.

But that's all moot, since you've agreed to make it optional (and thank you for that). And I thank you and the rest of the team who have decided to take on D3D11 implementation (especially the terrain height generation and collision detection aspects). I am really looking forward to playing in this sandbox when it's done!

:cheers:
 

asmi

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Continuing the discussion, when I think of lens flare I think not so much of rays, but of circles or rings repeating in a line intersecting the light source. Do you get those when you stare at headlights?
I mean something like that:
s125e012372.jpg


I am really looking forward to playing in this sandbox when it's done!
I don't think it will ever be done, since for every feature that we implement there are three more we're thinking of :tiphat:
So it's probably will be continuosly evolving. Allthough there are some bugs, right now I think it's stable enough to be playable - of course you need to save more often, and some builds are less stable than others - usually once we add new feature it became less stable until we fix some bugs and stabilize it, but then we're adding another feature... You know - it's always like that in constantly evolving projects ;)
 

Mandella

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Now you see, that effect is quite understated and reasonable to my opinion. I thought you were talking more like this:

(Warning. NSFW language in following link.)

http://questionablecontent.net/view.php?comic=2110

I should have a bit of spare time this weekend. I'll download the project and see if I can generate you some more bug reports!

:tiphat:
 

n72.75

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I think the one of the reasons that people like lens flares in that It gives the impression that the light-source is brighter than it actually is. With things like bloom and HDR, you can approximate how things should look to the human eye better. However, until they make LCD screens a LOT brighter, you'll never get the full experience of looking into the sun with your unprotected eyes from space.

EDIT:

Check this out: http://www.mpi-inf.mpg.de/resources/lensflareRendering/
 
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asmi

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Now you see, that effect is quite understated and reasonable to my opinion. I thought you were talking more like this:

(Warning. NSFW language in following link.)

http://questionablecontent.net/view.php?comic=2110
No, this is also possible, but I meant mostly rays like I've shown. Actually I sort of understand why effect like you've shown occurs and what causes it, but for the rays - I have no clue, but in order to model it appropriately I need to understand the science behind the effect, and have some quantitative description of effect (i.e. mathematical model).

I should have a bit of spare time this weekend. I'll download the project and see if I can generate you some more bug reports!

:tiphat:
That would be great. So far most of issues that were reported were mostly regarding visual glitches, all CTDs that were reported so far were caused either by some dll missing, or by outdated drivers :)
 

Mojave

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As regards to lens flare, I would enjoy it implemented as an optional feature so that one could enable, and disable it as desired. This would be a nice feature when one is recording a movie with orbiter for you tube.
 

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However, until they make LCD screens a LOT brighter, you'll never get the full experience of looking into the sun with your unprotected eyes from space.
:lol:
RGBUV
I enjoy Orbiter, but it's not worth going blind and getting skin cancer.
 

asmi

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:lol:
RGBUV
I enjoy Orbiter, but it's not worth going blind and getting skin cancer.
UV have nothing to do with brightness :)

Just so you know guys, instead of camera-like flare I'm thinking of implementing this thing: http://www.mpi-inf.mpg.de/resources/hdr/TemporalGlare/ Looks cool to me :lol: I'll have to cut some corners so it would work faster than original algorighm, but I'll try to figure something out.
 
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