I am trying to match the specularity size of an old Internal material (controlled by a Hardness value) and a new Cycles material (controlled by a Roughness value).
As can be seen in the image, Internal Hardness is not nearly as linear as Cycles Roughness is. But I can't find out what sort of math to do to the hardness to make it match the roughness - the Blender source code from the 2.79 era is unsearchable because it's historical, and I can't find any other hints as to what the "Hardness" value logically represents that aren't dead links.
- I'm not going for perfect accuracy. I just need the average person to look at the two rows here and think "yeah the shiny part looks the same size".
- The roughness numbers in the image are backwards because I'm actually working with gloss (the opposite).
- The max hardness in the image is 130 because that's what the Hardness texture input does at 1.0 power. I used the default CookTorr, but if one of the others is easier to work with or more accurate for this, that's fine.