It all happens on the Picture Plane, the flat surface of the format you are working with. You can create the illusion of spatial depth by mimicking the characteristics of space in the real world.

Perspective: Things which are farther away appear differently to us than those things nearby. These different qualities are described as perspective. The classic example of perspective shown below depicts railroad tracks, which are parallel, coming together as they stretch into the distance. They eventually seem to meet (an illusion) at a single place called the VANISHING POINT.

We are very quick to read the clues in any scene which indicate a spatial relationship between elements.

These two shapes vary only in size. Do you perceive the blue shape to be farther away than the purple shape? If you do, you are responding to a difference in relative size or SCALE. We are used to seeing similar objects become smaller when they are farther away.

Now which shape is closest? We know that an overlapping shape must be closer so the blue box is closer. The purple box is farther away but we now know it is the larger box.

This shape is taller on the right. Do you see it as a flat panel turned toward you? The top and bottom edges, if extended, would eventually meet at a vanishing point.

If another shape is added,does the panel become a cube? The top and bottom edges now would extend to vanishing points on either side of the format. This is called two-point perspective. The previous flat shape only indicated one-point perspective.

Atmospheric Perspective: We have become accustomed to the effect of the atmosphere on the sights we see. Looking at objects far away we also see the dust, haze, bugs, fog or smog in the air. This tends to mute, to dim, to diffuse the color and detail of distant objects.

This landscape shows an expanse of hills. We see them as going into the distance because they become dimmer in the distance (atmospheric perspective) and they get smaller (change of scale, a clue to linear perspective).

Trompe-l'oeil: This impessive term descibes an illusion created by making an element appear to be a real object resting on a surface. The object can be rendered in extremely fine detail to acheive this. The object can also be set off the surface by the rendering of a shadow.

Here is an example of trompe-l'oeil using the shadow effect to create the illusion of the graphics hovering over the web page.

This is a very flat appearing page design but it is accented by the icons which are inset into photorealistic sauce pans. This is trompe-l'oeil using only the fine detail technique.

Here is another primarily 2-dimensional design but it is spiced up with a few illusions of space. The logo overlaps the blue panel to bring it forward and the characters to the left of the logo pop off the flat surface with the illusion of trompe-l'oeil.