Once research is complete, ask students to make a 3-D image that looks like a hologram. Before beginning artwork, tell students it helps to understand how human eyes perceive space. When you look at a distant landscape, what do you notice? The colors seem dull, you see less detail, edges are not as sharp, and you see less contrast. Why? Because you are looking through the air, which has density. On overcast days, the effect is even more pronounced. This phenomenon is called atmospheric perspective.