Symbols and Instances in Flash

• A symbol is a graphic definition that can be used repeatedly in a composition. This is true not only in Flash but in CAD and other graphics programs.
• An occurence of a symbol is called an "instance"
• Each instance can have the following properties defined specifically for it:

Size, Shape, and Location:

• Scale (X and Y)
• Position (X and Y)
• Rotation (theta)

Color:

• Tint (individual weighting of R, G, and B channels)
• Brightness (-100% = full black, 0% = normal, +100% = full white)
• Alpha (transparency, 0% = completely transparent, 100 = completely opaque)
• The combined values of these properties define the state of the instance.
• In Flash, an animation typically includes one symbol type per layer.
• The keyframes in that layer include parameters for various states of the symbol.
• A motion tween between two keyframes calculates the intermediate frames by interpolating the property values between the states of those keyframes.
• In Flash, the default is for the interpolation to be even from one keyframe to the next. It can also be adjusted ease in (slower at the beginning) or ease out (slower at the end).

	Symbol definition in library.
	Insert Symbol in lower left. Add frame at frame 24. Move symbol to upper right Right click on the area between the frames and select Create Motion Tween Move the play head left and right to see the motion.
	Move the play head to the first frame Click Window > Transform. Set Rotate to 30. Set vertical scale to 50%
	Move the play head to the last frame frame Use the Transform palette to set the rotation angle to zero, and the scale factor to 50% both horizontally and vertically. In the Properties tab in the upper right, select Color Effect Select alpha from the drop-down menu. Use the slider to set alpha to zero. Move the play head to see the animation.
	The Animation.

Why Symbols, Instances, and Keyframes are Good

• The ingredients for an animation are:
  • A set of symbol definitions.
  • A set of keyframes with state parameters (position, scale, color, etc.) for each.
  • Tweening instructions

• Using those, Flash can calculate every frame of the animation.
• This requires much less data than a digital video (e.g. Quicktime or avi), which stores a complete digital image for each frame.

Using Flash for Dynamic Montage with Photographs