Flash Lecture 3:Masks

Dr. Harry Witchel

Masks• Masking is a 2 layer system (like guides) in which the upper layer

controls what part of the lower layer can be seen• This technique is useful for appearances/disappearances, “spotlight”

effects and “magnifier” effects• The Upper layer is mask (e.g., black)

– Each pixel will be all or none– It is invisible in final movie– Mask is a layer property (right click to make a layer a mask)

• Parts of the lower layer are revealed by what is present above• Either layer can be moving (tweens)• Masking does not work until you make a “published” version of the

movie (i.e., control-return)

Appear Effect Using a Mask

Spotlight Effect Using a Mask

Exercise: Make an ECG movie with a mask

• 3 layers, each 40 frames• Bottom layer: Graph paper lines• Middle layer: masked layer of ECG trace.

– This layer has no animation or tween on it– In frame 1 draw the ECG trace with the pencil tool

• Top layer: Mask layer with motion tween. – In frame one make a symbol that is a rectangle as large as the stage,

and locate it to the left of the stage– In frame 40 make another keyframe and move the box symbol rightward

so that it covers the entire stage– Tween the frames between frames 1 & 40 (either a motion tween or a

classic tween)• Right click on top layer and middle layer and select properties, then

make top layer a mask and middle layer masked• When you run the movie, you should see blank graph paper, and

then the ECG trace should appear on it