Height Fog Highlighting Certain Objects?

I’m kinda pulling my hair out at this point.

I have certain objects that seem to get a stronger highlight from height fog, and I can’t figure out why.

For example, see attached picture.

The lighter purple bar is the same material as the rest of the building, yet it gets a strange sheen as it’s approached in UE4.

I’ve noticed this happens if I scale objects up, but I’m not sure why this happens?

Any insight appreciated.


I think you can just change the inscattering color to black, or much darker.

Then it will just be highlighting those same objects with black, unfortunately. It’s not the highlighted color I’m confused about, it’s why it’s doing it at all and only for some objects.

My guess is that your material is either Bad,
Or that you intentionally set the specular value and the roughness values to a point where they are actually causing the light to bounce.

Your materials should probably ignore object size for tiling situations anyway.
Realistically, it depends on how the material and the object UVs are set up.

check all of the different rendering modes, starting with Unlit to make sure the colors and values are actually the same.

If all of the different modes show you the same thing, but the end result is not as in the picture, then it has to do with light and how it’s being applied to the object(s).

is it possible you’re using DFAO and this being an AO problem rather than a fog problem?
otherwise you might want to describe your lighting setup a bit more (baked or dynamic?), and show what your material is doing

Did you use defer render or forward render ?
If it’s forward render, it happens when your object is not enough vertex because Height Fog in forward use vertex depth to calculate fog.

So it’s actually the same material. The entire building is just pulling from a tileset for colors.

Lit is what I already showed, unlit looks fine, detail lighting looks the same as lit, lighting only has it go dark, which looks normal, looks like it removes the fog entirely and then it doesn’t do it.

I don’t think so; I don’t have

Lighting is entirely dynamic using only a skylight.

The material seems to be reflecting more of my purple-ish fog than other things in the scene; it’s the same material across the entire building though, just using a tileset.

Here is unlit;

And in my previous picture you can see how the first little step of the building seems to get a highlight when I have the height fog on.

Deferred rendering.

In the scene “show” settings, I can turn off everything in lighting features and lighting components, and the weird purple highlight persists.


Additional image with fog settings pumped up to highlight the lip of that building that’s having a weird fog interaction.

Also; this happens to even a default plane in this scene; if I just place a basic plane and scale it up, the fog starts to affect it more heavily? I don’t know why height fog would do that?

Any insight appreciated.