faceForward

Orients a normal vector n to face towards an incident vector i, using a reference normal nRef to determine the orientation.

It's typically used in shading calculations to ensure a normal vector consistently points "outward" from a surface, relative to an incident vector (like a view vector or light vector).

The logic is as follows:

• If the dot product of the reference normal nRef and the incident vector i is negative (dot(nRef, i) < 0f), it means i is hitting the "front side" of the surface (the side from which nRef is pointing away). In this case, the original normal n is returned, assuming it's already oriented correctly for the front side.

• Otherwise (dot(nRef, i) >= 0f), i is hitting the "back side" of the surface (the side nRef is pointing towards), or is tangent to it. In this case, the negated normal -n is returned, effectively flipping n to orient it correctly for this side.

The goal is to produce a normal that, when dotted with i, would typically yield a negative value if i is considered a direction towards the surface (e.g., a view ray).

Parameters