BARY
THE BOX'S MAIN HELP:
This is the three barycentric coordinates of the intersection in the hit primitive. The fourth value will be for patches. Barycentric coordinates are the weight of each vectex. The sum of all barycentric coordinates is one.
X (output):
This is the contribution of all the x vertex values.
Y (output):
This is the contribution of all the y vertex values.
Z (output):
This is the contribution of all the z vertex values.