ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Using the drawing API
Winding rule names
Flash Player 10 and later, Adobe AIR 1.5 and later
The names refer to a more specific rule that defines how these fills are managed. Positively wound paths are assigned
a value of +1; negatively wound paths are assigned a value of -1. Starting from a point within an enclosed area of a
shape, draw a line from that point extending out indefinitely. The number of times that line crosses a path, and the
combined values of those paths, are used to determine the fill. For even-odd winding, the count of times the line crosses
a path is used. When the count is odd, the area is filled. For even counts, the area is unfilled. For non-zero winding, the
values assigned to the paths are used. When the combined values of the path are not 0, the area is filled. When the
combined value is 0, the area is unfilled.
A B
Winding rule counts and fills
A. Even-odd winding rule B. Non-zero winding rule
Using winding rules
Flash Player 10 and later, Adobe AIR 1.5 and later
These fill rules are complicated, but in some situations they are necessary. For example, consider drawing a star shape.
With the standard even-odd rule, the shape would require ten different lines. With the non-zero winding rule, those
ten lines are reduced to five. Here is the ActionScript for a star with five lines and a non-zero winding rule:
graphics.beginFill(0x60A0FF);
graphics.drawPath( Vector.([1,2,2,2,2]), Vector.([66,10, 23,127, 122,50, 10,49,
109,127]), GraphicsPathWinding.NON_ZERO);
And here is the star shape:
A B C
A star shape using different winding rules
A. Even-odd 10 lines B. Even-odd 5 lines C. Non-zero 5 lines
And, as images are animated or used as textures on three-dimensional objects and overlap, the winding rules become
more important.
Last updated 6/6/2012
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