Fresnel / Fac

I would like to know the exact (!) correlation between these two buttons. The english dokumentation is a kind of “unspecific”, saying that Fac is a “controlling factor”. But what does he controlls exactly and how.

The Fresnel controls the fresnel angle (less means less unreflective angle) and the Fac controls the blending factor (less means more blended) of the fresnel.

Thank you. Does anyone have some mathematic information about this issue

A friendly person gave it to me on blendpolis. In some kind this is a progress for me because now I now exactly what I don`t understand :slight_smile:

/* mix of ‘real’ fresnel and allowing control. grad defines blending gradient */
float fresnel_fac(float *view, float *vn, float grad, float fac)
float t1, t2;

if(fac==0.0f) return 1.0f;

t1= (view[0]*vn[0] + view[1]*vn[1] + view[2]*vn[2]);
if(t1>0.0f) t2= 1.0f+t1;
else t2= 1.0f-t1;

t2= grad + (1.0f-grad)*pow(t2, fac);

if(t2<0.0f) return 0.0f;
else if(t2>1.0f) return 1.0f;
return t2;

Purely mathematic information? Wikipedia is your friend :wink: