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NiGoea

A talk about global illumination approaches

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Hi all,

I was thinking about what algorithms are nowadays used to go beyond the classic direct illumination algorithms.
I talk about games like Crysis and Stalker.

What do they use to obtain such a good graphics on open spaces ?

Shadow maps and SSAO are classic approaches (and maybe simple), but very limited expecially in open spaces. On the other hands, direct light approaches are very limited. And those games seem to have something more than the classic point and spot lights model.

I know algorithms like photon mapping, instant radiosity and PRT, but I don't know if they are actually used of not.

I'm working on an FPS.

Let's talk about it ;)

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Crysis doesn't use any GI. Just direct lighting, shadow maps, and plenty of SSAO. Crysis 2 has their "propogated light volumes" or whatever they call it which is all real-time, but I don't have many nice things to say about it. I don't know anything about STALKER or what they use.

Tons of games use radiosity + light maps. The "radiosity light maps" approach created by Valve is still very popular, in fact pretty much all UE3 games use a variant of this technique. SH lightmaps have also been used with great results. (see Bungie's Halo 3 materials presentation). PRT is probably less popular, at least at runtime. At work we use PRT as part of our baked lighting pipeline to store transfer functions per vertex, and it works great. We also use it for a "preview mode" where the artists can tweak the environment lighting in real time before they do a final bake.

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thanks for the link

Quote:
Original post by MJP
Crysis doesn't use any GI. Just direct lighting, shadow maps, and plenty of SSAO.


I can't believe it. The only way in order for they to achieve such graphics is an extensive use of lightmaps. But how can they with that big areas ?

Quote:

Tons of games use radiosity + light maps.


Yes, light maps turn out to be a good solution, but I personally don't like them.

So are they the final solution used from AAA games to obtain realistic graphics ?

I remember I read somewhere that Far Cry 2 uses some sort of indirect lightning

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Quote:
Original post by MJP
Crysis 2 has their "propogated light volumes" or whatever they call it which is all real-time, but I don't have many nice things to say about it.


Have you tried it? I'd be very interested in hearing the 'bad' things you have to say about it, because I always was surprised how well it seemed to work, considering the potential problems with lacking occlusion, coarse resolution, etc. Would be interesting to hear the weaknesses from the point of view of an independent developer.

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Quote:
Original post by NiGoea
thanks for the link

Quote:
Original post by MJP
Crysis doesn't use any GI. Just direct lighting, shadow maps, and plenty of SSAO.


I can't believe it. The only way in order for they to achieve such graphics is an extensive use of lightmaps. But how can they with that big areas ?



It's certainly possible to achieve without light maps, considering that's how they did it. :P


Quote:

Tons of games use radiosity + light maps.


Yes, light maps turn out to be a good solution, but I personally don't like them.

So are they the final solution used from AAA games to obtain realistic graphics ?

I remember I read somewhere that Far Cry 2 uses some sort of indirect lightning[/quote]

Nothing is the "final" solution, it's just one of the most popular and robust. If you're going to pre-bake lighting information you've got to store it somehow, and that usually means either per-vertex or in light maps. Light maps can be tricky, but they decouple the resolution of your stored lighting data from the resolution of your geometry which can be a big win. Plus you can take advantage of texture filtering. Whether they suit your needs depends on your game, and perhaps also on whether you have access to a good lightmap solver (or have the time/expertise to make your own).

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Quote:
Original post by macnihilist
Quote:
Original post by MJP
Crysis 2 has their "propogated light volumes" or whatever they call it which is all real-time, but I don't have many nice things to say about it.


Have you tried it? I'd be very interested in hearing the 'bad' things you have to say about it, because I always was surprised how well it seemed to work, considering the potential problems with lacking occlusion, coarse resolution, etc. Would be interesting to hear the weaknesses from the point of view of an independent developer.


No I haven't prototypes it myself, I've only read the papers and looked at the screenshots. So feel free to take my comments with a grain of salt. :P

Anyway I think it's pretty neat and has good results considering it's completely dynamic with no preprocessing steps. But from what I've seen you can still achieve much better results (and cheaper!) from pre-baked solutions. So it really comes down to whether you need completely dynamic geometry + lighting...and for us the answer is "no, definitely not". If that were a design requirement, LPV would probably be at the top of our list.

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