25 July 2010
When you shape-tween complex shapes in Adobe Flash Professional, you can use shape hints to specify points that should correspond to the starting and ending shapes. For example, if you tween a drawing of a key that morphs into a lock, you can use a shape hint to mark the bottom point in both shapes to keep the objects from becoming an amorphous tangle while the shape change takes place.
Shape hints contain letters (a through z) for identifying which points correspond in the starting and ending shapes. You can use up to 26 shape hints.
Shape hints are yellow in a starting keyframe, green in an ending keyframe, and red when not on a curve. Shape hints work best if you place them in counterclockwise order beginning at the top-left corner of the shape.
In the examples above, the 5 morphing into a 3 turns inside out as the shapes tween; shape hints applied to the L morphing into the Z ensure that the letter remains recognizable throughout the animation.
To add shape hints to a shape tween, select the beginning keyframe and choose Modify > Shape > Add Shape Hint. Move the shape hint marked (a) to the desired point. Then select the last keyframe in the tweening sequence. Move the shape hint marked (a) to the point in the ending shape that should correspond to the first point you marked. Test the animation and then move the shape hints to fine-tune an animation. Continue adding more shape hints as needed.
To view all of the shape hints, select View > Show Shape Hints while the shape tween's keyframe is selected. To remove a shape hint, drag it off the Stage.
To learn more about working with shape hints, see the section titled Control shape changes with shape hints in the Flash documentation.