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In the reference manual, the specular value (Principled BSDF) should be ((IOR-1)/(IOR+1))^2/0.08. I want to make a glass with Cycles. So, I am using a transmission value of 1 and an IOR of 1.45. I have calculate the specular value (0.42) and I have set it. However, if I change the specular value to anything between 0 and 1, I don't get any change in the render... the reflection is the same.

If the transmission is 0, the specular value works well and the reflection changes... but when it is 1, it doesn't work.

Why is the specular value not working in principled bsdf when the transimssion value is set in 1?

Thank you very much.

Edit: In the reference manual, why the equation IOR-1/IOR+1... is it shown. if the specular parametter does not work with transmission?. if I'm not mistaken, the index of refraction only works with objects like water, glass... so, what is the point of the equation?

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  • $\begingroup$ The specular term is separated into a "glass reflection" and "non-glass reflection". Transmission is a lerp factor between them. Transmission=1 means the specular term = "glass reflection". The Specular input only affects the "non-glass reflection" though. $\endgroup$
    – scurest
    Commented Jul 13, 2021 at 18:05
  • $\begingroup$ Then, If I want to create glass, water... What should I use? A different transmission value (1-specular)? $\endgroup$
    – Juan de Dios
    Commented Jul 13, 2021 at 19:01
  • $\begingroup$ Trasmission=1, put your IOR in IOR, and ignore Specular? $\endgroup$
    – scurest
    Commented Jul 13, 2021 at 19:16
  • $\begingroup$ But, I think the reflection with transmission = 1 is very high for a glass. I would like to control the quantity of reflection. On the other hand, in the reference manual, why the equation IOR-1/IOR+1... is it shown. if the specular parametter does not work with transmission?. if I'm not mistaken, the index of refraction only works with objects like water, glass... so, what is the point of the equation? Thank you $\endgroup$
    – Juan de Dios
    Commented Jul 13, 2021 at 20:17
  • $\begingroup$ Dunno, you should probably edit those questions into your main question though. $\endgroup$
    – scurest
    Commented Jul 13, 2021 at 20:19

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