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Sunbeam effect - how does it work

Started by Harry Hunt Jan 12, 2008 at 3:54 PM 3 replies 1.5k views

Original Post

Jan 12, 2008 at 3:54 PM

I've played Crysis and now I've seen a video of the upcoming FarCry 2 and both of those games feature a pretty neat volumetric sun ray effect.Check out this screenshot to see what I mean. I'm not entirely sure how this is implemented. I read somewhere that it's done using raytracing but of course that's pretty vague. Does anybody know of any papers or articles explaining the effect? Thanks a lot in advance.

coderchris

Jan 12, 2008 at 5:21 PM

I believe that there is a nice article in GPU gems 3 that explains a technique that is close to, if not basically the same, as the technique used in crysis. I dont believe that the technique mentioned in GPU gems is based on raytracing, though i dont have the book on me so im not completely sure

MJP

Jan 12, 2008 at 9:52 PM

My guess would be that they do it by blurring towards the sun, checking the depth buffer along the way for occlusion.

Zipster

Jan 12, 2008 at 11:20 PM

The article coderchris refers to is "Volumetric Light Scattering as a Post-Process" by Kenny Mitchell, in GPU Gems 3. The basic idea is to trace a ray from each pixel to the light source in image-space, and use the number of occluders you hit as an attenuation factor. There are a bunch of other small details, but that's the general idea. You can pick up a copy of the book for more information, it's definitely worth it :)

Harry Hunt

Jan 13, 2008 at 2:37 AM

awesome. Thanks everybody!

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