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schupf

Godyrays/Lightshafts

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Hello, I have two questions about godrays/lightshafts: 1) Whats the reason for godrays being visible? I searched a lot but couldnt find a single site which explains the physics about godrays. I guess it have something to do that some parts of the air are some kind of shadow volume (a volume with a low amount of photons traveling through). I hope somebody of you knows something about the physics of godrays! 2) How could I implement them in a real-time rendering system? Thanks!

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http://en.wikipedia.org/wiki/Crepuscular_rays
http://www.atoptics.co.uk/atoptics/ray1.htm
http://www.ems.psu.edu/~demark/471/CrepuscularRays.html

Found this too: http://www.youtube.com/watch?v=N6r6tbf4UGU

"Light shaft rendering as described in my 2007 GPU Gems 3 article on Volumetric Light Scattering as a Post Process"

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Quote:
Original post by schupf
Hello,

I have two questions about godrays/lightshafts:

1) Whats the reason for godrays being visible? I searched a lot but couldnt find a single site which explains the physics about godrays. I guess it have something to do that some parts of the air are some kind of shadow volume (a volume with a low amount of photons traveling through). I hope somebody of you knows something about the physics of godrays!

2) How could I implement them in a real-time rendering system?

Thanks!


I don't think there is much to say... atmosphere is not perfectly transmissive, there is dust in the air, different gas, pollution and so on). These things reflect light just like the glas of a mirror would, so where there is more light the air is more brilliant and where there is shadow it is darker... I suppose this describes the effect you were refering to.
Hope this helps

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