Some Actions require directional information to guide ZBrush to results you are looking for. When hovering over the polygons or points of your model you will notice visual widgets that represent directional information.
ZBrush’s selection system has a priority order: Each time that an element is highlighted, ZBrush considers its position relative to the surrounding geometry. When highlighting a vertex, ZBrush also looks at the adjacent edges and faces while doing any calculations. Some Targets (like Polyloop when used for a Poly Action) rely detection of the adjacent edges to determine in which direction the Action will function. The Edge Selector Widget simply makes this “sub-element detection” visible.
Highlighting a Point:
An orange line extending from the point indicates the direction of the Action operation. Along with this point, some Actions will also look at the face that is highlighted when hovering over the point. If the selected Action needs directional information it will refer to these two widgets. Simply move the cursor around the point to change the direction of the widget and thus, the Action.
Highlighting an Edge:
There is no indication of direction needed when working with edges as the edge by itself gives the direction. However, hovering over an edge will highlight faces as well. Some Actions also use the edge’s midpoint to determine their direction.
Highlighting a Polygon:
An orange line located between the highlighted polygon’s center and edge closest to the cursor indicates the direction of the Action operation. Moving around the poly will change which edge this line points to.