http://sidneys77crlfslcr7zmj3msmxchgnxhrxlp3p3kbaswo7twchjnicid.onion/programming/2022/03/23/raytracing.html
We create the ray at origin x=x, y=y, z=0 , and set the direction to x=0, y=0, z=1 . The direction is what we call a unit vector , which means that the overall magnitude to the vector is 1 (\(\sqrt{x^2+y^2+z^2}=1\)).