My latest art work is a realistic pencil drawing of a glass of water. Drawing a glass is not that difficult. The artist needs to pay attention to different values and how each section is placed in relationship to each other.
An optical illusion can mostly be seen in the mid section of the glass. Light bends the image so that we see parts of the bottom of the glass. The water line also gives away the presence of water inside the glass. I plan to create a free tutorial that will teach you how to draw the glass.