Just wanted to give a big thanks for this incredible post... All this info well explained and all together... Awesome!
Thanks man, really appreciate it :)
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Reflectivity / IOR sheetLINK TO SHEET HERE, you have to make a copy to make changes!
I keep telling people to leave "Reflection Level" at 1, no matter what. Until Corona 1.5 this couldn't really be done, because the GGX was capped at 0.3 glossiness, and no matter what glossiness you used, F0 didn't dim. To compensate for this you had to reduce "Reflection Level", and fake the IOR. (or use my IOR LUT)
Corona 1.5 has finally fixes this issue, we still have the black rim of death around our objects (for now), but we can dim F0 with glossiness, aka PBR material.
So how can you use my sheet to convert your "none PBR" materials to PBR ?
Maybe you have reduced the "Reflection Level" value or maybe you have used a Bitmap, maybe both ?. This is how you fix it!
How to fix a material with reduced "Reflection" BitmapThis material has 1.52 IOR and a bitmap in "Reflection".
Take a printscreen of this bitmap and paste it in Photoshop.
Create a rectangle selection
Do a Blur > Average
Sample this value
Input the values into my sheet. The IOR is actually 1.44 (About 3% Reflectivity).
How to fix a material with reduced "Reflection Level" valueFirst of all, I want to say that this is NOT how I would create a metal.
So we have 0.5 "Reflection Level" and 10 IOR.
Input the values into my sheet. The IOR is actually 3.75
So what have we learned ? Leave Reflection Level alone ! Just leave it alone :'( (Not at 0, but at 1!)