In class, we ran through an example of a ray that doesn't intersect with the plane, and through the calculations, we got t = 0. Is that always the case for a non-intersecting ray? Does a non-intersecting ray always generate 0 or it can generate anything that's not c?
If the ray does not intersect the plane, then (N^T . d) should be zero, because the ray has no component in the direction normal to the plane. That is the situation to check for the edge case.