Hi, guys. Yesterday, I saw a post on Reddit showing a glass material. In the post, the OP showed the shader nodes. While i was reading the shader setup, one thing caught my attention: the Fresnel input. Specifically, if the factor input has a range between 0 and 1, why did the OP connect an IOR value of 1.5 to the factor input? Is this process correct or not?
Furthermore, is the Light Path node necessary to create realistic glass, or not?
Lately, I’ve been a bit confused about why some people connect certain inputs to the Factor (Fac) socket.
This is a complex setup for glass which creates diffraction. That’s why you see several glass shaders with various IORs - each color will appear slightly shifted and thus creating diffraction. Then this setup uses a different setup when the path depth is greater than 8 (a simpler version) and for transmission.
Usually light path tricks are used to force glass to not cast shadow without the need of rendering caustics. IOR 1.45 - 1.5 are normal for glass.
This setup recreates a glass material from its separate components, refraction and reflection. The fresnel causes the shader to be more refraction than reflection when viewed from the front, but become increasingly more reflective at glancing angles.
Specifically, fresnel gives you the realistic, real-life gradient transition between the two depending on the IOR. The IOR isn’t going to be used as the final value, it’s there only to guide the calculation. The output of the fresnel node is in the 0-1 range.
