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https://github.com/patriciogonzalezvivo/thebookofshaders
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24 lines
716 B
Markdown
24 lines
716 B
Markdown
## Faceforward
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Return a vector pointing in the same direction as another
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### Declaration
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```glsl
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float faceforward(float N, float I, float Nref)
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vec2 faceforward(vec2 N, vec2 I, vec2 Nref)
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vec3 faceforward(vec3 N, vec3 I, vec3 Nref)
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vec4 faceforward(vec4 N, vec4 I, vec4 Nref)
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```
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### Parameters
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```N``` specifies the vector to orient.
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```I``` specifies the incident vector.
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```Nref``` specifies the reference vector.
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### Description
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```faceforward()``` orients a vector to point away from a surface as defined by its normal. ```If dot(Nref, I) < 0``` faceforward returns ```N```, otherwise it returns ```-N```.
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### See Also
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[reflect()](/glossary/?search=reflect), [refract()](/glossary/?search=refract)
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