several hatchings such as cross lines and dots are used to represent the depth within this portrait. as seen in this image the darkness of an area is shown by doing a much more of a closer/tight hatchings.
Grief, I’ve learned, is really love. It’s all the love you want to give but cannot give. The more you loved someone, the more you grieve. All of that unspent love gathers up in the corners of your eyes and in that part of your chest that gets empty and hollow feeling. The happiness of love turns to sadness when unspent. Grief is just love with no place to go. - Jamie from http://allmylooseends.com/2014/03/lights-wink/