LightmapCommon.usf LogBlackPoint Explanation

I’m generating my own lightmaps but I’m struggling to find the purpose of this line in the lightmap shader


const half LogBlackPoint = 0.01858136;

Why is this value needed and how can i get rid of it without changing the shader (using LightMapScale and LightMapAdd vectors)

Why you can’t modify shaders?

It would be stupid to use a custom engine just to change a shader, I was asking how to factor that value when encoding lightmaps. I’ve figured it out now anyway.

I’m also using my own encoded lightmaps and I’m just not using blackpoint when decoding. That’s how I get them to look as close as possible to true HDR lightmaps. If I want darker areas later on I just tweak the tonemapper’s toe.

I’m guessing there’s no way to do that without modifying the shader though?