Lightmap Gradient Problem

Prophet

Hello,

I would like to know if there's a way to remove this ugly gradients when you have Lightmaps with near black colors?



Enhanced contrast in Photoshop to be more noticeable what I mean:




I'm doing this with Unity, but since I saw this type of gradients in Left 4 Dead 2 as well, for example, I'm wondering this is a common problem.

Is there a way to fix this?

dirigible

the problem, as far as I can tell, is that you are using a very limited range of color in your lightmap (let's say, from 0 to 20 rgb). But then you're expanding that range back up with realtime lighting / post process / whatever. So you're taking 0 to 20 and turning it into 0-100. The result is gonna be banding.

Here's a visual representation.
I made a gradient, compressed it down to 0-20 rgb, then expanded it back up to 0-255.

Santewi

That's 8-bit textures in a nutshell for ya.

Prophet

But is there a way around it?

ZacD

Avoid near black colors and/or use post processes to darken the screen while using a wider color range for the actual light map.

Prophet

I've tried with a Post-Process, not changing the actual color of the lightmap, but the problem is still there. And about the dark colors, this needs to be really dark inside at some points.

dirigible

That's very odd that it's happening even if you're only darkening the scene with a post process effect.

Just to be sure we're talking about the same thing, you should light your scene like it's afternoon or something, then create a post process volume that darkens the scene to make it look like night time.

Ashaman73

There is not much you can do. If unity supports other texture formats (float,16bit,openexr) you can try to pimp the resolution. Although check if you use sRGB textures, these have a lower resolution for lower values, a standard none sRGB texture might help.

Dirigible ways is ok too, though you need to take care, that the bright places don't get toned down too, in this case you should use a none linear tone down, though if your overall scene is very dark this is the way to go.

Although desaturate your scene in dark places, the eye can't barely see colors in a dark environment, this could smooth the banding effect too (no color shifts).

And eventually use a texture, textures always help to break up artifacts .

Xendance

I'm guessing unity also compresses lightmaps with DXT, which certainly doesn't help you along with the problems stated above