This tutorial was prepared by Sketchfab user Thibaud Tournery-Bachel.
Below you will find a table with F0 and Reflectance values for creating different realistic materials.
- This is not real world data. I'm not a scientist, and I don't have any stuff to measure this based on real world.
- Everything is a basic math conversion based on other data found on the web (IOR at angle 0 with a wavelength of 1).
- I don't pretend this is perfectly accurate, because it doesn't need to be. Custom F0 is very subtle effect in most cases.
- Dielectrics only... of course.
- Metalness Workflow only. Specular Workflow already has control on F0.
How to use in Substance Painter?
- First of all, use this method only if you have significant dielectrics variations on your materials. Some examples: blood, wood and gems on the same map. Check the table to see if your materials have enough contrast to use a custom map.
- Add a new Channel to your project, and set it as a Linear 8-Bit (L8). By default, Reflection Channel will do the trick and is already set as a L8 map.
- Activate the Reflection channel on your materials and simply add the corresponding value from the table (between 0 and 1). For metals, just set the maximum value of "1" (for transition purposes).
- Remember to export your Reflection map, and name it "F0" or "Specular Level" in your Export Configuration.
- Use it in Sketchfab in the F0 map slot.
- You're done!
How to use without Substance Painter?
- If your material only has one dielectric, or several with close values, just check the table and use the dominant value directly on the Sketchfab F0 slider (multiply by 100). For example, if you only have a rock, just push the slider to 49 (0.49 on the table).
- You can do that for each material you have. So two materials can have different F0 value.
Purpose of F0
- F0 has a very subtle effect in most case, but yet still a nice effect. Just remember that other maps will play a bigger role.
- If you're running after optimization, you probably don't want to use that map.
- F0 will react nicely with dynamic lighting and moving objects. Static objects with static lighting are less obvious.
- F0 is almost useless at far distance, but enhance your details at close and very close range.