Draw curved segments by dragging the object
anchor points with Pen Tool. When you use the Selection tool to
select an object anchor point connecting curved segments, the segments
display direction lines, which end in direction points.
The angle and length of the direction lines determine the shape
and size of the curved segments. Moving the direction lines reshapes
the curves. A smooth point always has two direction
lines that move together as a single, straight unit. When you drag
the direction point of either direction line on a smooth point,
both direction lines move simultaneously. Pen Tool maintains a continuous
curve at that object anchor point. In comparison, a corner
point can have two, one, or no direction lines, depending
on whether it joins two, one, or no curved segments, respectively.
point direction lines maintain the corner by working independently
of one another. When you drag a direction point on a corner point’s
direction line, the other direction line, if present, does not move.
Direction lines are always tangent to (perpendicular to the radius
of) the curve at the object anchor points. The angle of each direction
line determines the slope of the curve. The length of each direction
line determines the height, or depth, of the curve.