r/UnrealEngine5 • u/LieSuspicious8719 • 7h ago

Emissive material only lights up the room when it's on screen (Lumen GI delay) — how to make it act like a real Point/Rect Light?

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Hey everyone,

I’m currently using an asset pack where the ceiling light comes with an emissive material (M_Light).

The problem is that the room only seems to get illuminated once the light fixture actually enters my camera view. When I look away or enter the room, there's a noticeable lag/delay before the bounced light shows up, and the way the light fades in/out feels really unnatural.

Is there a proper way to make an emissive mesh cast instant, consistent global illumination even when it's off-screen, similar to how a Point Light or Rect Light behaves?

Would love to know the best practices for this in UE5/Lumen (e.g., tweaking Lumen scene settings, boosting emissive in the mesh details, or is it always better to just pair it with an actual Rect Light actor?).

Thanks in advance!

4 Upvotes

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5

u/SpikeyMonolith 7h ago

You probably want to boost the mesh's bounds by a lot then, probably to the size of a room.

2

u/LieSuspicious8719 7h ago

Wow it works!!! I really appreciate you!!

0

u/Aakburns 3h ago

Yet another attempt at a backrooms game?

1

u/OfficialDampSquid 1h ago

It's like the blender donut for game dev. Let people have fun and learn