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Alundra

Screen-Space Reflection, enough or mix needed ?

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Hi,

Using Screen-Space Reflection you have nice result but of course if something is not on the screen, you don't see in reflection map.

Is it enough or a mix is needed to do a classical render to texture ? Where one or other should be prefered ?

For the PBR screen-space reflection is enough ?

Thanks

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Depends on the visual requirements of your game. Do you often have scenarios where you can't get any proper samples for your screen trace? If so, does it have a significant impact on your game's visuals?

 

If so, you could definitely look into a traditional cubemap based approach where you sample from your cubemap whenever you're not able to resolve a screen-space path. This is what a lot of modern AAA games do these days.

 

As for PBR, what technique for generating your reflections has nothing to do with whether your shading is physically based or not. How you resolve your sampled reflection data however does, and how you want to make it fit within the constraints of a physically based shading model is completely up to you.

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Imagine your main character in front of a mirror and the camera is behind the character. That's it. There's a massive amount of information unavailable to SS reflections.

 

They need to be complemented by a more powerful technique unless you're planing on using reflections just to spice up background stuff

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unless you're planing on using reflections just to spice up background stuff

I think this is a really good niche for screen-space reflections - they aren't really that much use in first or third-person games where you can walk up to a mirrored surface. But they do work really well as an environmental effect for anything that's rendered from a top-down view.

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The other commenters have pretty much mentioned this already, but there is very limited information in screen space, so yes you need something to fallback to when using screen space reflections.  In Matias's example, you'd want to use something like planar reflections on the mirror surface to reflect the scene since the data would otherwise not be present.

 

I'm not sure how self-promotion is looked at around here, but I wrote this blog post a while back that is pretty relevant to what you're trying to learn about.  Specifically, search for the word "fallback" - you'll see that it's brought up a lot!  Screen space reflections can look good, but they can also have jarring discontinuities that can ruin the bigger picture.  Using parallax-corrected environment maps can help.  You'll need to blend between ray hits and misses from your SSR for the transition between SSR and fallback not to be too noticeable.

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For PBR you're better off even with a simple skybox "reflection", maybe combined with a low-res cubemap for actual world reflections. SSR in my experience works well in just a handful of situations (for instance, a flat floor/ceiling, water on the ground, basically anywhere where the information loss is minimal).

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