This phenomena is called “Opposition Surge/effect”, and is a result of the phase angle between a light source (sun) and the observer approaches zero. The effect is mostly seen on rough surfaces, as the shadows of said surface disappear when the observer is directly between the surface and the light source
This is something I’ve been trying to simulate in a material. Now this effect should in theory be achieved simply by creating rough physical geometry, however, it is not very practical for large scale scenes as the physical geometry takes up a lot of memory. Can anyone think of a way to simulate this effect within a material?