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Something to look at during night flights...

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Something to look at during night flights...

Postby Thorsten » Mon Aug 10, 2015 6:17 pm

You're going to love seeing this dynamically - pics can't really convey the impression properly. Each flash lasts a split second and is possibly followed by a second one immediately, then it starts somewhere else on the front, all illuminate part of the surrounding clouds, and then all fades back into darkness... This looks way cool in actual motion.

Image

Image
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Re: Something to look at during night flights...

Postby LesterBoffo » Mon Aug 10, 2015 6:23 pm

So I'm taking it this is for night time thunderstorms? Since most lightning is cloud to cloud this is a good fix. Too bad it wasn't included with 3.4
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Re: Something to look at during night flights...

Postby gsagostinho » Mon Aug 10, 2015 9:17 pm

LesterBoffo wrote in Mon Aug 10, 2015 6:23 pm:Too bad it wasn't included with 3.4

I think you meant 3.6. Well, it's a pity, but then again we already have a nice feature for 3.8 ;)

@Thorsten Looks really cool indeed! I will check it in the sim :)
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Re: Something to look at during night flights...

Postby Thorsten » Tue Aug 11, 2015 8:51 am

Image

Anyone up to making a decent set of lightning textures? The one we have in the repository is *cough* not optimal.
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Re: Something to look at during night flights...

Postby tigert » Tue Aug 11, 2015 10:28 am

How about generating textures with a L-system fractal? I am not sure if it makes sense to do this at runtime, but maybe we could make reasonable textures this way? http://drilian.com/2009/02/25/lightning-bolts/

This page seems to explain the different "stages" of the lightning strike: http://hyperphysics.phy-astr.gsu.edu/hb ... igseq.html - it might look more realistic if there were a few frames with roughly the same path but slight alterations in the more detailed shape of the bolts?

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Re: Something to look at during night flights...

Postby gsagostinho » Tue Aug 11, 2015 11:33 am

@Thorsten I will give it a shot :) By the way, where is the location of the current image in the repository? I did a git pull right now but I can't find it.

@tigert Well, I wouldn't bother with fractals to be honest since generating them in real-time would be superfluous in my opinion. Then it's up to the person creating the texture how he wants to create, the only point is to select a good looking texture regardless of the technique employed in the creation.
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Re: Something to look at during night flights...

Postby Johan G » Tue Aug 11, 2015 12:52 pm

tigert wrote in Tue Aug 11, 2015 10:28 am:... it might look more realistic if there were a few frames with roughly the same path but slight alterations in the more detailed shape of the bolts?

gsagostinho wrote in Tue Aug 11, 2015 11:33 am:@tigert Well, I wouldn't bother with fractals to be honest since generating them in real-time would be superfluous in my opinion.

Also I doubt most people have frame rates enough to see all the components of the lightening strike over time, perhaps with the exception of more extreme thunderstorms. :wink:
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Re: Something to look at during night flights...

Postby legoboyvdlp » Tue Aug 11, 2015 1:38 pm

Is this in 3.7 and latest fgdata? Will it be soon? Cant wait!
Cmon thunderstorms pay me a visit to my town
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Re: Something to look at during night flights...

Postby Thorsten » Tue Aug 11, 2015 3:03 pm

Should be on next (i.e. 3.7) now.

By the way, where is the location of the current image in the repository? I did a git pull right now but I can't find it.


Models/Weather/lightning.rgb

It's been there for a long, long time...

My current plan of attack is to have several *.ac models (rects with a texture) stacked in the *.xml file and use select animations to show only one of them - some higher resolution would be nice...

How about generating textures with a L-system fractal?


Cool from a math POV, but probably easier to just extract from real-life imagery or simply draw by hand.

Note that the lightning bolt registers as a non-zero value of /environment/lightning/flash - and in the same subdir, you get the relative position of the event to the current eye point. If a clever aircraft modeler knows the speed of sound, he can use that to time an event for a thunder ambience sound... I'm just saying...
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Re: Something to look at during night flights...

Postby Thorsten » Tue Aug 11, 2015 5:52 pm

Some more to enjoy ;-)

Image

Image
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Re: Something to look at during night flights...

Postby Johan G » Wed Aug 12, 2015 4:27 am

Thorsten wrote in Tue Aug 11, 2015 3:03 pm:Should be on next (i.e. 3.7) now.

gsagostinho wrote in Tue Aug 11, 2015 11:33 am:By the way, where is the location of the current image in the repository? I did a git pull right now but I can't find it.


Models/Weather/lightning.rgb

It's been there for a long, long time...

My current plan of attack is to have several *.ac models (rects with a texture) stacked in the *.xml file and use select animations to show only one of them - some higher resolution would be nice...

A decent resource seem to be NOAA's photo library. A Google image search for "lightening site:photolib.noaa.gov" might yield some inspiration. Note that most of those images, though probably not all, are public domain. Unfortunately many of them seem to have been taken with filters.
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Re: Something to look at during night flights...

Postby gsagostinho » Wed Aug 12, 2015 10:43 am

@Thorsten in your pictures above it seems you are using lightning.rgb, but we already have two much better looking lightnings in fgdata: in the same directory, look for lightning01.rgb and lightning02.rgb. Did you try using them? If so, can you tell me what is wrong with them so I can try to improve them?

Sorry but I am away for these next weeks and it's has been difficult to find time to do anything related to FG, so it may take a while for me to try to create a new texture for this :(
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Re: Something to look at during night flights...

Postby Thorsten » Wed Aug 12, 2015 1:37 pm

in the same directory, look for lightning01.rgb and lightning02.rgb


Thanks for pointing me to my own work :-) If you look at the timestamp, they're a few hours old (and if you look at the commit message, you'll find that I found Johan's NOAA link very helpful).

There's nothing wrong with them - but there could still be more and better varieties.
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Re: Something to look at during night flights...

Postby LesterBoffo » Wed Aug 12, 2015 5:03 pm

what would be an optimal images size in pixels for the quad, 256X512 ? and would it be easier on frame rates with a .png versus .rgb?
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Re: Something to look at during night flights...

Postby Thorsten » Wed Aug 12, 2015 5:27 pm

what would be an optimal images size in pixels for the quad, 256X512 ? and would it be easier on frame rates with a .png versus .rgb?


Cloud texture sheets containing multiple clouds are typically 1024x1024, so 512xsomething seems quite enough, all else is probably an overkill. For weather we always use *.rgb textures because they load faster - once loaded into GPU memory, there is no framerate difference, but weather cycles a lot of stuff in and out of GPU memory.

The textures are extracted from the images, completely de-saturated and then using the light curves to get the background to black onto which color to alpha is used. A slight halo around the bolt can actually remain and looks cool, but the edges of the sheet need to go to full transparency, so I used eraser around.

The bluish color is added later procedurally.

Here's one of the new textures in action:

Image

(I guess it's really one of the things you need to see in action to fully appreciate... pictures really don't do the impression justice)
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