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Flare effect


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#1 staticVoid2   Members   -  Reputation: 345

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Posted 24 September 2013 - 02:36 AM

Hi there,

 

I recently implemented a basic headlight light flare effect into my game (similar to the image below) using simple billboarded sprites but was wondering what the technical name for this effect is so I could look into it a bit more. Every tutorial I've seen only tells you how to render this effect but does not go into any details of the theory behind it.

 

KLF-headlights.jpg

 

Any links to some more information on this would be great thanks.



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#2 3TATUK2   Members   -  Reputation: 730

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Posted 24 September 2013 - 03:48 AM

i think "relativistic aberration", and if not - it's possibly even a form of lens flare happening on your eye


Edited by 3TATUK2, 24 September 2013 - 03:52 AM.


#3 Hodgman   Moderators   -  Reputation: 38614

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Posted 24 September 2013 - 03:51 AM

I've often seen this kind of lens flare effect referred to as a 'corona'. They usually are just billboard sprites, with some tricks, like usin some kind of occlusion test at the centre instead of the usual depth testing.

However 'corona' isn't a very useful search term... E.g. Searching "corona billboard" shows me pictures of beer advertisements!

#4 staticVoid2   Members   -  Reputation: 345

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Posted 24 September 2013 - 04:03 AM

It's not so much the lens flare but the initial flare effect which I believe can be witnessed without looking through a camera. If you look at a street lamp at night you will notice a distinctive flare around the light source. I'm not sure what to call this effect though.



#5 ShadowFlar3   Members   -  Reputation: 1258

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Posted 24 September 2013 - 04:40 AM

Could you mean halo?



#6 Hodgman   Moderators   -  Reputation: 38614

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Posted 24 September 2013 - 05:47 AM

It's not so much the lens flare but the initial flare effect which I believe can be witnessed without looking through a camera. If you look at a street lamp at night you will notice a distinctive flare around the light source. I'm not sure what to call this effect though.

There's two overlapping effects around a street lamp at night.

One is a lens flare -- in your original picture of the car, the radial lines, doughnut-shaped rings and the central glow are a lens flare.

 

This part of the effect will fade/shrink as you raise your hand and cover the street lamp / light-bulb from your view.

 

After covering the street-lamp with your hand / thumb, the first glow will disappear (as it's occurring in your eye/lens), but the second one will remain. This is a large halo around the light (not really present in your first picture), caused by particles in the air scattering the light. On humid/misty nights, or in polluted areas, this effect will be more pronounced as there will be more of these scattering particles.

Ideally, this would be rendered as a volumetric halo, or a regular point light affecting a volumetric fog.



#7 InvalidPointer   Members   -  Reputation: 1493

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Posted 24 September 2013 - 07:56 AM

Could you mean halo?

 

And specifically, lenticular halo phenomena?

 

EDIT: From what I recall, there's not a whole lot of theory on the subject because there's actually some controversy as to what is actually taking place in our eyes, but I don't know if that's still the case. I *do* know there's another successor paper to the linked that actually generates animated halos by way of a super-detailed simulation that tries to account for small particles floating around in the vitreous humor, but sadly I can't locate it with some basic Google searching :(


Edited by InvalidPointer, 24 September 2013 - 08:01 AM.

clb: At the end of 2012, the positions of jupiter, saturn, mercury, and deimos are aligned so as to cause a denormalized flush-to-zero bug when computing earth's gravitational force, slinging it to the sun.

#8 Kryzon   Prime Members   -  Reputation: 3539

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Posted 24 September 2013 - 02:53 PM

Some more resources: 

http://daio.daionet.gr.jp/~masa/rthdribl/index.html

http://daio.daionet.gr.jp/~masa/archives/GDC2003_DSTEAL.ppt

http://daio.daionet.gr.jp/~masa/archives/GDC2004/GDC2004_PIoHDRR_EN.ppt



#9 LancerSolurus   Members   -  Reputation: 627

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Posted 24 September 2013 - 05:47 PM

It's real easy to create that effect in the real world. Squint your eyes, your eyelashes will cause it. If you wear glasses, wipe it with something with a little oil on it (your body oil on your shirt works fine), the streaks will be perpendicular to the direction of the wiping. A recently cleaned windshield that isn't fully clean will work just as good. It can be caused both by a fresnel effect and a reflection effect.


Edited by LancerSolurus, 24 September 2013 - 05:48 PM.

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#10 Bacterius   Crossbones+   -  Reputation: 10906

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Posted 24 September 2013 - 11:53 PM

The physical name for the effect which accounts for at least the long streaks + the ring structure, is a diffraction pattern, caused by Fraunhofer diffraction as incident light waves diffract off the aperture of your eye system (i.e. glasses + contacts + eyebrows + cornea + any other foreign body such as dirt and whatnot) and bleed onto your retina.

 

I guess it probably goes by more trendy names in the photographic industry happy.png


“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”


#11 tonemgub   Members   -  Reputation: 1755

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Posted 25 September 2013 - 02:52 AM

http://en.wikipedia.org/wiki/Diffraction_spike

 

Here's a thorough article - not sure if it covers this specific effect: http://www.telescope-optics.net/eye_aberrations.htm

 

But in general, I guess any visual effect that is caused by the human eye is called an "eye aberration", so you can probably start with this term to find more specific names for what you're reffering to...

 

Also, thanks to JJ Abrams, the terms "anamorphic lens flare" or "anamorphic lens effect" have become famous recently. :)


Edited by tonemgub, 25 September 2013 - 04:03 AM.





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