Planes

Since we are learning to draw. we need to understand that objects exist in space. To illustrate on a 2D surface what we see in 3D we need to understand the picture plane.
There are three planes, a foreground midground and background. Keeping that in mind, we need to always consider that things in the background recede and things in the foreground become more prominant. Tone is one way to make things have the illusion of moving forward or receding in space. How things are placed and paying attention to how things overlap one another is another way to help us create the illusion of a third dimension in our drawings. There are also directional cues that we need to pay close attention to that we can use as guides in further understanding and creating believable images.