What happens to colors of a normal map when we sample them in shadergraph?

[od3098]

My original tangent space normal map is like this (light blue):

when I sample that in shadergraph or amplify shader editor it becomes more dark blue and its still in tangent space:

and when I try to bake this (or any other normal maps) from shader and save it to a file, the darker version will be saved.
P.S. The process of saving is done by applying normal result to BaseColor slot and Graphics.Blit into a renderTexture.

So what is the reason of darker colors and how I can have access to the light blue version to save it?

[od3098]

Part of the probable answer based on this video in OpenGL

RGB Colors are between 0 and 1.
Normal vectors are between -1 and 1.
So to convert RGB data to normal vectors, we need to multiply RGB values by 2 and subtract by 1.
This is probably what Sample node does to a normal map in shadergraph or amplify shader editor and in order to have the original texture data, we need to convert it back to values between 0 and 1 (add one and divide by 2)

this will get a close results to the original texture, but not the exact same one.
Not sure why…

[Oxeren]

You can just set the Type of the Sample Texture 2D node to Default.

[od3098]

Yes, but I want to keep it in normal mode cuz this method only works if the texture is not set to Normal map in import setting. And this is not always desired.

[od3098]

Ok, I have found the solution.
The result of the formula is the correct one. when I tried to save the texture and compare, that I was using:

RenderTexture.GetTemporary(resolution.x, resolution.y);

This renderTexture is in sRGB color space and the original texture was made in linear space.
so when I render in Linear space using:

new RenderTexture(resolution.x, resolution.y, 24, RenderTextureFormat.ARGB32, RenderTextureReadWrite.Linear);

the rendered png texture is almost exactly the same as the original one.