http://www.guerrilla-games.com/presentations/Valient_Killzone_Shadow_Fall_Demo_Postmortem.pdf

http://www.guerrilla-games.com/presentations/Drobot_Lighting_of_Killzone_Shadow_Fall.pdf

New Killzone have three different methods for reflections. First screenspace reflection is used and if that fails then it try to find is that point inside of static local cube map AABB and use that instead. If both these fails global skycube is used. Add some smooth tweening instead of binary fail and result should be good enough in most cases

I've never seen screenspace reflections work "very well". By its very nature you are missing any and all information not directly onscreen, and anything but purely reflective (zero roughness in whatever BRDF you're using) will also be problematic, as you vastly increase the chance your sample isn't onscreen.

SS reflections can work OK in the case of rain as a kind of planar reflection hack on the ground, where it's not too noticeable that you're missing a ton of reflectivity, you've got a layer of water for reflectivity you don't have to take roughness into account for, and you've got a strong fresnel effect hiding everything as well. But playing around with it, it's not really a "solution" for reflections, just a nice piece of eye candy you have to control very tightly (or compensate for at every turn ala Killzone).

Even on a lake or other body of water, you've got strong reflections a lot of the time, if your player can control the camera they'll say, look down at the water and as they do far reflections will just clip out entirely as the reflected areas leave screenspace before the water reflecting them does, and you'll just have a blank area where reflections should be. And that's just one scenario that will happen all the time. It's a rather ugly hack all in all.

I see screen space reflection more an occlusion technique for ambient speculars than reflection technique.

Basically stripped down version would just check reflection ray against depth buffer to determine is ambient specular cube used or not.

I've never seen screenspace reflections work "very well". By its very nature you are missing any and all information not directly onscreen, and anything but purely reflective (zero roughness in whatever BRDF you're using) will also be problematic, as you vastly increase the chance your sample isn't onscreen.

SS reflections can work OK in the case of rain as a kind of planar reflection hack on the ground, where it's not too noticeable that you're missing a ton of reflectivity, you've got a layer of water for reflectivity you don't have to take roughness into account for, and you've got a strong fresnel effect hiding everything as well. But playing around with it, it's not really a "solution" for reflections, just a nice piece of eye candy you have to control very tightly (or compensate for at every turn ala Killzone).

Even on a lake or other body of water, you've got strong reflections a lot of the time, if your player can control the camera they'll say, look down at the water and as they do far reflections will just clip out entirely as the reflected areas leave screenspace before the water reflecting them does, and you'll just have a blank area where reflections should be. And that's just one scenario that will happen all the time. It's a rather ugly hack all in all.

You've made your dislike of SS reflections pretty well known at this point, but I really can't agree with you. Yes, they aren't perfect. Neither is SSAO, for the exact same reasons, and yet SSAO is infinitely better than no AO, which is why just about every game now uses it. The same goes for reflections.

The reflections in Killzone 4 look pretty amazing, thanks in part to their use of SS reflections.

I've never seen screenspace reflections work "very well". By its very nature you are missing any and all information not directly onscreen, and anything but purely reflective (zero roughness in whatever BRDF you're using) will also be problematic, as you vastly increase the chance your sample isn't onscreen.

SS reflections can work OK in the case of rain as a kind of planar reflection hack on the ground, where it's not too noticeable that you're missing a ton of reflectivity, you've got a layer of water for reflectivity you don't have to take roughness into account for, and you've got a strong fresnel effect hiding everything as well. But playing around with it, it's not really a "solution" for reflections, just a nice piece of eye candy you have to control very tightly (or compensate for at every turn ala Killzone).

Even on a lake or other body of water, you've got strong reflections a lot of the time, if your player can control the camera they'll say, look down at the water and as they do far reflections will just clip out entirely as the reflected areas leave screenspace before the water reflecting them does, and you'll just have a blank area where reflections should be. And that's just one scenario that will happen all the time. It's a rather ugly hack all in all.

You've made your dislike of SS reflections pretty well known at this point, but I really can't agree with you. Yes, they aren't perfect. Neither is SSAO, for the exact same reasons, and yet SSAO is infinitely better than no AO, which is why just about every game now uses it. The same goes for reflections.

The reflections in Killzone 4 look pretty amazing, thanks in part to their use of SS reflections.

Oh certainly, with a lot of help they're ok. Just using it by itself though is the problem, as I said that lake scenario would cause any player to just shake their head sadly. And if you're going with screen space reflections and cubemaps, you'll do a lot better, but your scene is now mostly static by default.

I guess I'd just like a really good engineering solution, something that you can say "ok, this works for everything everywhere all the time" and you don't need X to back it up. But until then, if you're doing something like Killzone, then it can look solid enough.

I guess I'd just like a really good engineering solution, something that you can say "ok, this works for everything everywhere all the time" and you don't need X to back it up.

I think path tracing meets that criteria.

It is sort of like Heisenberg's uncertainty principle in a way. You can't have a general solution that works well for all scenarios and is computationally cheap at the same time.