mirror of
https://github.com/patriciogonzalezvivo/thebookofshaders
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34 lines
977 B
Markdown
34 lines
977 B
Markdown
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## Refract
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Calculate the refraction direction for an incident vector
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### Declaration
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```glsl
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float refract(float I, float N, float eta)
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vec2 refract(vec2 I, vec2 N, float eta)
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vec3 refract(vec3 I, vec3 N, float eta)
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vec4 refract(vec4 I, vec4 N, float eta)
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```
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### Parameters
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```I``` specifies the incident vector.
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```N``` specifies the normal vector.
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```eta``` specifies the ratio of indices of refraction.
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### Description
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For a given incident vector ```I```, surface normal ```N``` and ratio of indices of refraction, ```eta```, refract returns the refraction vector, ```R```.
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```R``` is calculated as:
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```glsl
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k = 1.0 - eta * eta * (1.0 - dot(N, I) * dot(N, I));
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if (k < 0.0)
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R = genType(0.0); // or genDType(0.0)
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else
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R = eta * I - (eta * dot(N, I) + sqrt(k)) * N;
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```
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The input parameters ```I``` and ```N``` should be normalized in order to achieve the desired result.
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### See Also
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[dot()](index.html#dot.md), [reflect()](index.html#reflect.md)
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