Interesting lighting...bug?

Hi everyone,

I started a small scene about a week ago that iv’e been working on part time just to take back into the swing of things in UE4 since it’s been a couple years.

It’s an upstairs hallway in a house with a single window at the end. So here’s my setup. I have a **Light Source **shining through the window with my bounce lighting, lighting quality, indrect ill all set to 10. I also had a **Rect Light **in that window to help boost the brightness, Skylight, finally I added a **Point Light **close to the camera for just a little added fill light. This point lights attenuation was the span of the wall with the intensity very low, like 0.1 or below. After bake everything looked great, and natural.

The issue arose when I decided to try and put a Rect Light under one of the doors to simulate sunlight in the room shining through. I started playing with the intensity and quickly realized I had been tweaking my Rect Light from the window and messed up what I had set it to. I realized this after I baked and the scene was overblown. I kept trying to adjust this light lower and lower to get it back to what I had but the scene continued to be incredible overblown. Literally the only thing I had mistakenly adjusted from when it was last working was intensity. So I deleted the Rect Light from under the door, did some bakes, still overblown. I then deleted the window Rect Light, it was still overblown, then finally deleted the hallway Point Light and it went back to normal. At this point I only have my Light Source in the scene. From here I added back a single Point Light with a 0.1 intensity and BAM! overblown again, from an almost completely dark room to needing sunglasses. I even tried setting my point light to 0.005 and it was still massively blown out. I tried swapping out the Point Light for a Rect Light, intensity way down and the entire scene kept blowing itself out.

Adjusting the attenuation of the light as to not encompass the entire hall, only half the hall showed the desired results but once I increased it the light appeared to output 100x’s what I had the intensity set to. It doesn’t matter where I put the light, it blows out every single time. What frustrates me is that I couldn’t find an explanation online except for a post about UDK saying to clear the Swarm Cache which I dont know if you are still able to do? and another person that found out about the attenuation adjustment and was happy enough with that solution.

I don’t understand why a single light can go from looking like it’s intensity is set to 1 and after a bake looking like it was at 1000. Has anybody ever experienced this before? My settings were working fine for me, I changed nothing aside from mistakenly adjusting a window lights intensity

Update:

I did some tests on another computer with a test room I’d been tinkering with on my lunch breaks. I added a point light, baked and the same overblown look. I realized what the problem is though. Below, the first image was baked using “Production” while the second image was baked using “Preview”. I had started using Preview at home because the production bakes were seriously slowing down my computer and that’s about when my problems started.

Why are the lights so different in preview? if it’s not even close to an accurate representation of your scene, why does it even exist as an option?