Different edge types can be displayed using different colors and linetypes. You can also add special effects, such as jitter and line extensions.
In a shaded or wireframe model, the visual style sets the visibility and appearance of isolines, facet edges, silhouette edges, occluded edges, and intersection edges. Facet edges (the edges between planar faces representing a surface) are displayed only when the angle between the facets is smaller than the crease angle value you specify.
Edge modifiers such as line extension and jitter, produce the appearance of a model that is still in the conceptual phase. Jitter makes lines appear as though they were sketched with a pencil. Line extension produces another kind of hand-drawn effect.
Occluded lines are hidden lines made visible by changing its linetype and color. In 2D View, you can change the display of occluded linetype with OBSCUREDLTYPE system variable and occluded color with OBSCUREDCOLOR system variable.
You can only change occluded color when the occluded lines are partially or completely visible.