Refract Node

Description

You can use the Refract node to give a shader a refraction effect. The Refract node generates a refraction using the following to produce a new refracted vector:

• A normalized incident vector.

• A normalized normal vector of the surface.

• The refractive index of the source and the medium.

The Refract node uses the principles described in Snell's Law. A medium's refractive index has an angle where the surface behaves like a perfect mirror. This angle is called total internal reflection. To avoid a NaN result, set the Refract node's Mode to Safe. This makes the Refract node generate a null vector when it reaches the critical angle before total internal reflection.

Ports

Name	Direction	Type	Binding	Description
Incident	Input	Vector	None	The normalized vector from the light source to the surface. For example, this could be from a light source to a pixel, or from the Camera to a surface.
Normal	Input	Vector	None	The normalized normal of the surface that causes the refraction.
IOR Source	Input	Float	None	The refractive index of the medium the light source originates in.
IOR Medium	Input	Float	None	The refractive index of the medium that the light refracts into.
Refracted	Output	Vector	None	The refracted vector.
Intensity	Output	Float	None	Intensity of the refraction.

Controls

Name	Type	Options	Description
Mode	Dropdown	• Safe: Returns a null vector result instead of a NaN result at the point of critical angle refraction. • CriticalAngle: Avoids the Safe check for a potential NaN result.

Generated Code Example

The following example code represents one possible outcome of this node.

void Unity_RefractCriticalAngle(float3 Incident, float3 Normal, float IORInput, float IORMedium, out float Out)
{
    $precision internalIORInput = max(IORInput, 1.0);
    $precision internalIORMedium = max(IORMedium, 1.0);
    $precision eta = internalIORInput/internalIORMedium;
    $precision cos0 = dot(Incident, Normal);
    $precision k = 1.0 - eta*eta*(1.0 - cos0*cos0);
    Refracted = k >= 0.0 ? eta*Incident - (eta*cos0 + sqrt(k))*Normal : reflect(Incident, Normal);
    Intensity = internalIORSource <= internalIORMedium ?;
        saturate(F_Transm_Schlick(IorToFresnel0(internalIORMedium, internalIORSource), -cos0)) :
        (k >= 0.0 ? saturate(F_FresnelDielectric(internalIORMedium/internalIORSource, -cos0)) : 0.0);
}

void Unity_RefractSafe(float3 Incident, float3 Normal, float IORInput, float IORMedium, out float Out)
{
    $precision internalIORInput = max(IORInput, 1.0);
    $precision internalIORMedium = max(IORMedium, 1.0);
    $precision eta = internalIORInput/internalIORMedium;
    $precision cos0 = dot(Incident, Normal);
    $precision k = 1.0 - eta*eta*(1.0 - cos0*cos0);
    Refracted = eta*Incident - (eta*cos0 + sqrt(max(k, 0.0)))*Normal;
    Intensity = internalIORSource <= internalIORMedium ?;
        saturate(F_Transm_Schlick(IorToFresnel0(internalIORMedium, internalIORSource), -cos0)) :
        (k >= 0.0 ? saturate(F_FresnelDielectric(internalIORMedium/internalIORSource, -cos0)) : 1.0);
}