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Is there a way to extend the SSGI effect beyond the camera view?

It seems that Screen Space Global Illumination doesn’t extend far enough to cover the entire screen. It seems to fade out at the edges of the screen, which is causing some ugly effects as seen in this video clip: Skylight Screen Edge Problem - YouTube

I am trying to figure out a way to still use SSGI since it dramatically increases the visual appeal of my levels. Any idea on how to extend SSGI beyond the camera’s view frustum?

Practically speaking the answer is no. Screenspace means it is working only with the data for what is in the gbuffers, which means it has no data about anything that isn’t visible to the camera which results in there being no light/shadow contribute for anything that isn’t directly on screen, this includes occluded objects though that’s not likely to be a common issue for a top-down game.

In theory, it is possible to do using brute force, by rendering at a larger resolution and then cropping the visible region so that the area it doesn’t have data for is limited. This is, of course, insanely expensive as a huge chunk of your render time is now spent on pixels that are not even visible to the user. On top of that it doesn’t fully resolve the problem, it just moderately mitigates it. Occluded meshes and large offscreen objects still won’t be correctly considered.

I’m not sure Unreal even has an easy way of implementing this, short of using a render target and a fullscreen mesh plane. Regardless, I would strongly recommend against it either way.

Your best option in my opinion is to either use baked lighting or DFAO

Thank you for the information you provided, Arkiras. That’s super helpful.

It indeed ran through my mind to try and mask the edges of the screen after rendering, but the drawbacks you mentioned definitely makes that seem unreasonable as a primary solution.

I will investigate DFAO and how I can use that to remedy the issue. Thank you for the answer. :slight_smile:

There’s also Light Propagation Volumes. I don’t know if they’re in UE5, though.

Light propagation volumes are deprecated now, right?

They’re still in 4.27.2 as far as I know. Does it restrict usage in saleable content or can you not then cook your game if you use LPV? I don’t know. It’d be a bit of a workload I bet to get them working for those problem areas though.