Are there shading methods that allow you to smoothly blend a texture into full blackness without those 'colour-bleeding' artifacts that can be seen on this picture:
Screenshot taken in Unity using URP 14+, but I tested 16+ for the same results, the scene lighting is pitch black apart from these two point lights. All ambient and environment light, fog are turned off.
Naturally to avoid appearance of those values for ambient light can be turned up. But it does cause the scene to lose depth, which then has to be compensated for with a fog, but then again it becomes impossible to reach really dark colours in Unity.
Same place, lit with ambient lighting, bleeding is gone.
But so is any sense of depth.
I can see how it can be a broader shading question unrelated to Unity per-se, because I have tried putting the same texture in Gimp and gradually lowering value curve for the texture color and in very low color region something similar begun to appear, a sort of contrasting colour split.
Strongly darkened texture right before 'bleeding' appears:
Some texture just an inch darker where the tonal balance of it is gone:
So tldr; the question is how to smoothly blend a texure into near-black colours without those 'bleedings' / colour splitting to appear? I guess the question is about possible math / shader code necessary to achieve that.
Consider closed, it was an issue of my laptop automatic bloatware 'update' which automatically enabled some sort of colour filter which introduced glitches into dark areas, which unfortunately happened before I worked in low light 3d conditions which made me not know that it shouldn't be like that.
For me thats what I've seen because of this screen filter:
It took me a week to find the reason for this, what helped was my friend called over the phone seeing this post and not knowing whats the difference between the pictures, so I am not deleting this post if anyone ever has similar issue.