Screen space Sun rays

Sun rays are bright light streaks that normally show up when the Sun is partially or completely occluded and rays of light stretch from the edges of the occlusion outwards. It is very common to see this phenomenon when thick clouds obscure the Sun and the rays are visible through the gaps between those clouds. This effect's scientific name is Crepuscular rays, but it goes by many other names such as God rays, Sun rays, and light shafts. In games, photography, and movies, it is not uncommon to see Sun rays either generate from a bright light source other than the Sun or due to occlusion from objects other than clouds. The following screenshot demonstrates how Sun rays can be seen when the Sun is occluded by an opaque object:

There are multiple ways to calculate light rays, each with different limitations and performance requirements. In this recipe, we will approximate the Sun light rays using a screen space calculation. As with all the other screen space techniques,...