Simple Drawing Effect Using Tweened Masks
By Ron Pesano


This is a simple drawing effect. The resulting file size is smaller than usingframe-by-frame animation. Basic knowledge of tweening and masking is required.

Open flash

Draw a stroked oval (the solid colour is transparent)

Add a keyframe at 80 frames

With the selection tool (white arrow) select 1/4 of the oval

Ctrl-x (to cut) the selection

Create a new layer

Ctrl-shift-v (to paste in place) the 1/4 oval in the new layer

Repeat the above steps 2 more times on the remaining sections of the oval until you have four 1/4 pieces of the oval.

Select layer 1. Create a new layer.

Draw a solid black box in the new layer covering the oval (this will be the first mask)

Convert the box to a symbol

Add a keyframe to the new layer at 20 frames

At the first keyframe of that layer add a motion tween

Move the box using the arrow keys so it does not cover the segment of the oval

Make that layer a mask and select "show masking"

Play the movie so you can see the start of the effect

Select the first keyframe of the next segment of the oval and while holding down the shift key drag the keyframe 20 frames down in the timeline

Repeat the above steps for the following layers one layer at a time until you have 4 masks covering the four segments of the oval

Some adjustment will have to be done on the timeline to get a smooth transition between the layers. Do this by shift-clicking both keyframes of the oval layer and the mask layer and dragging them back on the timeline by 2 - 3 frames. Season to taste and enjoy!

Editable movie in a zip file - download