slerpUnclamped
Performs unclamped spherical linear interpolation (slerp) between two 3D vectors.
This method interpolates along the shortest great-circle arc between two vectors. The interpolation parameter t is not clamped to 0, 1, allowing extrapolation.
Special cases handling:
When vectors are nearly parallel: falls back to linear interpolation.
When vectors are nearly opposite: uses a perpendicular rotation plane.
Return
Interpolated vector.
Parameters
a
Start vector (unit vector expected for accurate results).
b
End vector (unit vector expected for accurate results).
t
Interpolation/extrapolation parameter (0 = full a, 1 = full b).