Can I detect if the camera is looking to the left or right of the current heading?

[atomsinthevoid]

I need to establish a relative baseline for the 'center' Y rotation of the spline, that way if the camera is looking negative/positive of that number it will know the camera is looking left/right.

I'm hunting through the API but I'm a bit lost.

[_Aka_]

I am assuming that your camera is on the spline.
What you want is the sign of the signed angle between the spline tangent and the camera forward.
try this

Code:

var projectedCameraForward  =  Vector3.ProjectOnPlane(cameraForward, splineOrientationUp); // You should handle the cases where projectedCameraForward is Vector3.zero;

FluffyUnderware.DevTools.Extensions.Vector3Ext.AngleSigned(projectedCameraForward, splineTangent, splineOrientationUp)