Has anyone managed to successfully load an .nk file as a preset in the LuxCore Fresnel node?
At first, I managed to find a way to create a working header for this file so that it would load, but I got stuck on the ‘unparseable data’ exception, no matter how I formatted and separated the two digits for the values of n and k.
So?.. What’s the solution?.. What’s the format Sopra NK files have to be in? Don’t you want to help others who might be searching for a solution to this problem? What’s the point of posting in a forum then?..
[unit type code] [lambda lower value] [lambda higher value] [rows -2]
[lambda] [n value] [k value]
for example:
4 183 1180 4
0.18368 0.440000 0.407000
0.25048 0.302000 0.906000
0.33063 0.345000 1.320000
0.75143 0.265000 3.550000
1.18081 0.448000 5.580000
unit type code is:
1- electronovolts
2- micrometers
3- cm⁻¹
4- nanometers
this is for header lambda only i guess
By the way, it’s interesting just how flawed the rendering techniques are. I am sure the NK values are accurate and they just render like that, but those results give us the perfect opportunity to see that’s just not how those metals actually look.
That’s not how copper or gold or aluminum looks. We all know that instantly without any values or measurements as well 
Just from a quick glance. No measurements required. Just like that. Nope, that’s not how these metals look. 
Aluminum is sort of weirdly lighter than steel and is always covered with the white aluminum oxide:
Copper is way more saturated:
And gold is also very very different:
That’s how they actually look. You look at the images and just know. And when you look at that render with accurate NK values, it’s instantly clear they are off. Well, maybe aluminum looks OK, but it’s probably hard to screw that one up.
The apparent saturation depends mainly on the difference in k values for different wavelengths, the roughness, and the light source. In this test render, the light source was almost uniform, so there are no significant differences in absorption, and the roughness was set to a very low level, allowing reflections from the surroundings to be visible.
