Why does plugging the Fresnel into factor produce a Fresnel effect?

[Ben Gloger]

Sorry for such a basic question, but my understanding is that:

• In the Mix Shader, the Fac input is looking for a number
• This number determines how much to weight the two inputs below. A value of 1 is 100% the bottom input, a value of 0 is 100% the top input

So with that in mind, when we plug the Fresnel node into the Fac of the Mix Shader, is that just producing a number to mix between the two inputs? If so, why do we even need the Fresnel node? Couldn’t we just know to always put the Fac at 1.6 (or any other number)? Alternatively, wouldn’t any node that outputs a number of 1.6 suffice (or any other number)? 

Thanks!

Ben

[Dwayne Savage]

In terms of 3D software this is the angle of the face normal compared to the camera facing. Note the principal BDSF has this already build into it. So for example if you have a sphere and the camera is looking directly at its center. The center of the image would be 1. As you move to the outer edges of the sphere it will move towards 0. In the real world, beaches and lakes are the best examples.(it can also be seen in puddles) when you look straight down on the water you can see through it, but as you view it at an angle it becomes more reflective or mirror like. Hope that helps 

[Martin Bergwerf]

Hi Ben @bengloger ,

Your first assumption is not entirely correct;

the Factor can take a number, but it also accepts, for instance, different numbers per point…

In this example, the Noise Texture outputs a value between 0 and 1 for each point in 3D Space and so, depending on where a surface point lies in space, it gets its Color from the Mixing of blue and yellow, according to the Factor (that depends on the Noise Value at that point):

(There’s a lot more to it, but you’ll learn about that later…the main take away is, that the Factor can be more than just a single number.)

[Omar Domenech]

The thing is that when it comes to values, numbers and colors are interchangeable. Colors are made by values or numbers, if you want a 0 value somewhere, you can use the color black in its place, because the value for black is 0. And if you want a 1 value somewhere, you can use the color white and it will accept it since white is 1, 1, 1. So if you have Fresnel plugged in, it will go from white to black or you can also see it a going from 1 to 0 and there you have your values imputed for you.

[Ben Gloger]

This is great, thanks so much! This really helped solidify it “the Noise Texture outputs a value between 0 and 1 for each point in 3D Space.” Thanks again all! 

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