63 lines
3.4 KiB
Markdown
63 lines
3.4 KiB
Markdown
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# Refract Node
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## Description
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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:
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- A normalized incident vector.
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- A normalized normal vector of the surface.
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- The refractive index of the source and the medium.
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The Refract node uses the principles described in [Snell's Law](https://en.wikipedia.org/wiki/Snell%27s_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.
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## Ports
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| Name | Direction | Type | Binding | Description |
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|:------------ |:-------------|:-----|:---|:---|
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| Incident | Input | Vector | None | The normalized vector from the light source to the surface.<br/>For example, this could be from a light source to a pixel, or from the Camera to a surface. |
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| Normal | Input | Vector | None | The normalized normal of the surface that causes the refraction. |
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| IOR Source | Input | Float | None | The refractive index of the medium the light source originates in. |
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| IOR Medium | Input | Float | None | The refractive index of the medium that the light refracts into. |
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| Refracted | Output | Vector | None | The refracted vector. |
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| Intensity | Output | Float | None | Intensity of the refraction. |
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## Controls
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| Name | Type | Options | Description |
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|:------------ |:-------------|:-----|:---|
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| Mode | Dropdown | • **Safe:** Returns a null vector result instead of a NaN result at the point of critical angle refraction. <br/>• **CriticalAngle:** Avoids the **Safe** check for a potential NaN result. ||
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## Generated Code Example
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The following example code represents one possible outcome of this node.
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```
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void Unity_RefractCriticalAngle(float3 Incident, float3 Normal, float IORInput, float IORMedium, out float Out)
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{
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$precision internalIORInput = max(IORInput, 1.0);
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$precision internalIORMedium = max(IORMedium, 1.0);
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$precision eta = internalIORInput/internalIORMedium;
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$precision cos0 = dot(Incident, Normal);
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$precision k = 1.0 - eta*eta*(1.0 - cos0*cos0);
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Refracted = k >= 0.0 ? eta*Incident - (eta*cos0 + sqrt(k))*Normal : reflect(Incident, Normal);
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Intensity = internalIORSource <= internalIORMedium ?;
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saturate(F_Transm_Schlick(IorToFresnel0(internalIORMedium, internalIORSource), -cos0)) :
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(k >= 0.0 ? saturate(F_FresnelDielectric(internalIORMedium/internalIORSource, -cos0)) : 0.0);
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}
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void Unity_RefractSafe(float3 Incident, float3 Normal, float IORInput, float IORMedium, out float Out)
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{
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$precision internalIORInput = max(IORInput, 1.0);
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$precision internalIORMedium = max(IORMedium, 1.0);
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$precision eta = internalIORInput/internalIORMedium;
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$precision cos0 = dot(Incident, Normal);
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$precision k = 1.0 - eta*eta*(1.0 - cos0*cos0);
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Refracted = eta*Incident - (eta*cos0 + sqrt(max(k, 0.0)))*Normal;
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Intensity = internalIORSource <= internalIORMedium ?;
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saturate(F_Transm_Schlick(IorToFresnel0(internalIORMedium, internalIORSource), -cos0)) :
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(k >= 0.0 ? saturate(F_FresnelDielectric(internalIORMedium/internalIORSource, -cos0)) : 1.0);
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}
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```
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