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Strange rectangular lighting artifacts in large scene

I'm very new to lighting, but this seems like a pretty standard/simple setup to be having problems with. I'm lighting this hallway w/ 3 stationary point lights. What could be causing the rectangle artifacts?

One thing to note is that this hallway is pretty giant. Like, an airplane could fly through it easily. Could scale have anything to do with this? The floors and walls are standard floor and wall assets that come w/ UE4, just scaled up 10-20 times the normal size.

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Maybe worth noting that areas only lit by sunlight are perfectly fine.

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Product Version: UE 4.13
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asked Jan 21 '17 at 10:08 PM in Using UE4

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Ryan Darcey
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Hi rcdarcey,

This is actually a side effect of using large point/spot lights. You start to get banding like this when scaling these to cover large areas. https://docs.unrealengine.com/latest/INT/Resources/ContentExamples/Lighting/6_1/

You can adjust the shadow bias to help but, in that, you lose accuracy of the shadow casting surfaces.

For something like this I wouldn't use real world scale and would just scale everything smaller so that you get better results. You can avoid the inaccuracies and have better control of the lighting this way. Point/Spot lights aren't meant for this large area shadow casting and you reduce performance implications that can come with having them this large too.

I hope this helps.

Tim

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answered Jan 23 '17 at 03:57 PM

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Tim Hobson ♦♦ STAFF
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avatar image Ryan Darcey Jan 23 '17 at 09:30 PM

Hmmmm...gotcha. I'll see what I can do to reduce scale and adjust shadow bias, but is there a way to know exactly what target I should be hitting for "large" point/spot lights? What's too large?

Also, I wonder what the solution is for games that are played at two completely different scales? (ie. flying a big spaceship then exiting the spaceship and walking around)

avatar image Ryan Darcey Jan 24 '17 at 05:34 AM

For reference, I wanted to submit my point light settings here. When I changed the shadow bias from 0.5 to 5.0, my lighting artifacts disappeared. That kind makes sense considering all these default floor & ceiling assets are scaled up by about 10x.

My preference is definitely to build things around real world scale, but if there are going to be additional perf hits from having point lights with such large attenuation radii, it won't be a big deal for me to scale all assets down by a factor of 10.

Is the perf hit with large radii related to how many objects it affects, or is it literally just the high radius value? If it's just the number of objects it may affect, even though my game's scale is large, the object density should be the same as a game scaled to human size.

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avatar image Tim Hobson ♦♦ STAFF Jan 24 '17 at 04:57 PM

Point/Spot lights aren't meant to be these overarching large lights for a scene so that's why you get these artifacts, especially if it's a large mesh. They are more expensive based on the number of affecting objects they have as well. You could try increasing the resolution of shadows with r.Shadow.MaxResolution to 4096 but with that comes more performance costs.

If it's just a matter of lighting this hallway area I would say just using static lighting so that you get a nice light bake sans the artifacts from the large radius of the dynamic lights.

Increasing the shadow bias will reduce the artifacts, but you lose accuracy the higher you go. If that doesn't matter as much that's a route that is ok to take as well.

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