Lecture 13: Global Illumination & Path Tracing (24)
NicholasDrian
Another reason for sampling points on the light instead of sampling a hemisphere uniformly is that sampling a uniform hemisphere when the scene is full of point lights would yield a black image.
shreyaskompalli
It also just makes intuitive sense to only sample points on the light, since this is how the rest of the scene gets illuminated. The light source(s) are the reasons that we can actually see anything in the scene at all.
Another reason for sampling points on the light instead of sampling a hemisphere uniformly is that sampling a uniform hemisphere when the scene is full of point lights would yield a black image.
It also just makes intuitive sense to only sample points on the light, since this is how the rest of the scene gets illuminated. The light source(s) are the reasons that we can actually see anything in the scene at all.