Adobe After Effects CS3 - Manual (Page 336)

AFTER EFFECTS CS3
User Guide
331
Line Join options for strokes
The Line Join property for a stroke determines the appearance of the stroke where the path suddenly changes
direction (turns a corner).
Miter Join A pointed connection. The Miter Limit value determines the conditions under which a beveled join is
used instead of a miter join. If the miter limit is 4, then when the length of the point reaches four times the stroke
weight, a bevel join is used instead. A miter limit of 1 causes a bevel join.
Round Join A rounded connection.
Bevel Join A squared-off connection.
Fill rules for shapes
A fill operation works by painting color in the area defined as inside a path. Determining what is considered inside
a path is easy when the path is something simple, like a circle. However, when a path intersects itself, or when a
compound path consists of paths enclosed by other paths, determining what is considered inside is not as easy.
After Effects uses one of two rules to determine what is considered inside a path for the purpose of creating fills. Both
rules count the number of times that a straight line drawn from a point crosses the path on its way out of the area
surrounded by a path. The nonzero winding fill rule considers path direction; the even-odd fill rule does not.
After Effects and Illustrator use the nonzero winding fill rule as the default.
Self-intersecting path with Fill Rule set to Non-Zero Winding Fill Rule (left) compared with Even-Odd Fill Rule (right)
Even-odd fill rule If a line drawn from a point in any direction crosses the path an odd number of times, then the
point is inside; otherwise, the point is outside.
Nonzero winding fill rule The crossing count for a line is the total number of times that the line crosses a left-to-right
portion of the path minus the total number of times that the line crosses a right-to-left portion of the path. If a line
drawn in any direction from the point has a crossing count of zero, then the point is outside; otherwise, the point is
inside.
A more intuitive way to think of the nonzero winding rule is to think of a path as a loop of string. A point is
considered outside the path if you can put your finger at that point and then pull the string away without it being
caught, wrapped around your finger.
Because the nonzero winding fill rule takes path direction into account, using this fill rule and reversing the direction
of one or more paths in a compound path is useful for creating holes in compound paths. To reverse a path’s
direction, click the Reverse Path Direction On
button for the path in the Timeline panel.