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Light in between two mesh

I have two meshes that are overlapping together, this supposed to give me a shadow that covers the directional light illuminated from behind these two meshes but there is still a light that passed through in between them, the two meshes behind the chairs have two sided lighting but the floor isnt.

what am i missing out on? alt text

Product Version: UE 4.21
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asked Mar 08 '19 at 01:34 PM in Rendering

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3 answers: sort voted first

Maybe have a look on your lightmap UVs - this could be some bleeding from the lit areas from behind the wall..

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answered Mar 08 '19 at 01:48 PM

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avatar image Mirge24 Mar 08 '19 at 02:50 PM

standard 512 and i've generated lightmap UVs with min light map resolution of 512, how to avoid i've tried certain methods

avatar image Dividuum Mar 09 '19 at 11:45 AM

But it looks like the one wall is not standing straight on the other.. such non-perpendicular angles could be the reason.. Maybe you also could put some geometry on the other side to block the light?

avatar image Mirge24 Mar 09 '19 at 07:31 PM

ah yeah i tried this just now, kind of a fix really all you need is a higher res lightmap for that mesh behind the walls, and the walls are 90degree angle specifically hehe cheers

avatar image Dividuum Mar 10 '19 at 07:08 AM

Ok, just decided to draw what I meant (crappy mouse art incoming). Not sure of cause if this is your problem, just my guess.

The blue colored pixels on the picture are pixels that could be hit from both sides of the wall. Your wall doesn look perpendicular (when looking from above) to the UVs, as your tile texture isn't. That could (could!) be the source of your artifacts, but I don't know enough about your scene (I don't know whats behind the wall or what the real angles between these two are).

Well hope that helps.

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mouseart.jpg (126.5 kB)
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Looks like "standard" light bleeding. Are the walls thick enough? Are you using dynamic or static lighting?

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answered Mar 08 '19 at 02:29 PM

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avatar image Mirge24 Mar 08 '19 at 02:47 PM

the walls are static lighting and there's also a back face as well, i tried duplicating the walls and rotating it the otherway then reverse culling the duplicated copy to provide that thickness, bleeding is still visible

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Could you show us the lightmap uvs for those meshes that you experiencing the bleeding? /floor, wall/ Your walls/floor... shouldn't overlap but edge snapped for best results!

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answered Mar 08 '19 at 03:15 PM

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avatar image Mirge24 Mar 09 '19 at 07:32 PM

turns out it just needs a wall behind so it could cover the light bleed with a higher rest lightmap a normal cube would do wonders

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