Since recently, EnvironmentDiffuseScale property of Lighting doesn’t work well with custom skyboxes, as parts in the distance appear with wrong shading—opposed to parts close to the camera, which appear fine. This is best seen with a dark skybox, and when a place has just been loaded.
In the videos above, you can see how parts have blue shading, as if they were receiving diffused light from the default, blue sky skybox. I’d expect the shading to be mostly black instead, not blue. You can see that it is indeed shading from the EnvironmentDiffuseScale property of Lighting, as the blue shading fades away once I lower its value.
Interestingly enough, adjusting any property of the Sky object twice will force-update the EnvironmentDiffuseScale to apply shading from the current skybox and fix the issue completely.
Since when & Repro
This bug isn’t old. I haven’t seen it a few days ago.
It works exactly the same no matter whether you play the game or when you open the place in Studio. It isn’t place-specific, too.
Here’s a Sky.rbxm (1.0 KB) object I’m using that you can insert into Lighting to see the bug (remember to adjust EnvironmentDiffuseScale until the blue shade appears)
Edit: Cutting the Sky object out and pasting it back resets the shading, in case you want to repeat fixing it without leaving the place.
It all looks as if the Sky object isn’t loading correctly. I noticed that the blue shade appears right when I open the place up (before the custom skybox is loaded), disappears as soon as the custom skybox loads, then reappears for a short period of time, and disappears for parts in relatively close proximity. I’m not exactly sure, as I don’t have footage of opening that place before the bug, but I don’t recall any blue shades on loading, or that the custom skybox would be loading for so long.
I’m also 90% sure that this place’s thumbnail didn’t have the default skybox in the background a week ago, but my memory could be playing tricks with me (yes, it did have the same custom skybox applied back then, I haven’t changed it in months)