When a ray hits an object, in addition to reflected and refracted rays, rays to the light sources must be generated to determine shadows, intensity of illumination, etc.
(a ray; hits; an object) (rays to the light sources; must be generated; to determine shadows, intensity of illumination, etc.; T:When a ray hits an object)
a ray rays to the light sources
hits must be generated
an object
to determine shadows, intensity of illumination, etc. T:When a ray hits an object