Lightmass: A random light becomes super bright

Since upgrading to 4.7 I started to see a strange phenomenon: When rebuilding lighting on a map a random light becomes too bright. Which one changes each time I rebuild. Sometimes it’s a light component in a blueprint, sometimes it’s a standard spotlight actor. So far I’ve only seen static lights affected. The scene is inside an importance volume.

4.7.3 binary on windows 7 64 bit.

Hi ZoltanE -

I realize that you are getting different results, but can you post a screenshot of the issue in the engine. Also what are your post process settings and lighting setup in the level which is causing this issue? Does this issue occur in a blank or Template Project?

Any Additional Information that you can think of would be helpful -

Eric Ketchum

Here is a screenshot of what I’m seeing:

http://zspline.net/temp/Clipboard%20Image%20(44).png

When that selected light is turned off then it’s all cool. (The lights are cloned, have the same settings.)
If the light is turned on then the left corner gets very bright. (Built on medium or high.)

I couldn’t reproduce the issue on an empty level but managed to migrate this map into an empty project:
https://drive.google.com/file/d/0B_6w1d6KT30XY0hLdXpDMmFXNjA/view?usp=sharing

Open the LightingBug map and see if toggling the WallSpot_Fishy light makes a difference for you.

A few things to note:

  • Deleting all reflection captures or the (unlit) skysphere fixes the lighting for some reason.
  • Turning on all the WallSpot lights either fixes the issue or relocates the blown out spot to the corner at the right on the screenshot.
  • There are PointLights outside the room and the importance volume. They have a huge radius but they are so far away that they should not affect the room at all. Turning them off fixes the problem too. Maybe a rouge photon wandering into the room causes the splash of extra light?

Hi ZoltanE -

You have gotten some bad lightmass data stored in your Intermediate and Saved Folders. Delete those folders and go into your level and rebuild your lighting as you want it and all should be correct. Please let me know if the problem is not corrected.

Thank You

Eric Ketchum