@ifcruickshank Sopra-sa has been down for quite some time, but you can find the database in the internet. I have a copy if you need. Refractiveinfo.org and filmetrics.com websites are online, just go there choose the material you want and download the data file.
@cekuhnenyes, basically it gives you the correct fresnel values based on nk input. But it jumps the steps of finding the correct value for each color component wavelength from the interpolation of the sample data. If you ever tried to do it, you know that it’s slow and boring.
Apart from the shader functionalities for render, I wrote this node with a few details in mind. First, it doesn’t fill your node groups list from the add menu with nodegroups. Second, tangent and normal inputs don’t need to be connected for the node to work. Third, it doesn’t add any event handlers, and integration with cycles nodes is seamless. These are common problems that nodegroups suffer, and I tried at all costs to avoid them.
@moony not that I haven’t thought about it. It would still be slow but it’s possible to optimize the internals of the node based on the user input. Must test to see if it makes any difference from what I’ve already done.