Create a basic Mask animation to do animation of bottle of coca cola getting empty
1.Open a new flash document, in a timeline click on layer1 & draw an empty bottle. Take the new layer2 & draw a fill colored rectangle using from rectangle tools take the new layer3 & draw a fill colored bottle.
2.Hide the layer1 & layer3 in the timeline using or lick on the show/hide all layer option in the timeline at this time only the rectangle is display on the stage then click on layer2
3.Click on any frame as per your choice(for e.g. 45,50,----) & press f6( insert keyframe)
4.Click on free transform tool & drag the rectangle at the end point then click on the frame1 & right click & apply create motion tween
5.And also show the layer1 & layer3 in the timeline by clicking on them.
6.Right click on layer3 & apply mask at this time automatically mask is also applied on layer2.
7.Select layer3 click on the same frame of layer2 & press f5 also select layer1 click on the same frame of layer2 & press f5.
8.Save your work using (ctrl+s) & test the movie (ctrl+enter).
