#faceforward

return a vector pointing in the same direction as another.

#Declaration

• float faceforward(float N, float I, float Nref)
• vec2 faceforward(vec2 N, vec2 I, vec2 Nref)
• vec3 faceforward(vec3 N, vec3 I, vec3 Nref)
• vec4 faceforward(vec4 N, vec4 I, vec4 Nref)

#Parameters

• N: Specifies the vector to orient.
• I: Specifies the incident vector.
• Nref: Specifies the reference vector.

#Description

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.

#See Also

• reflect
• refract