What is Custom Animation?: Part I
Custom Animation is a feature in Microsoft Office PowerPoint. It contains a list of effects that you can apply to objects to have them animate during the slide show. With the release of PowerPoint 2002/XP, more effects are introduced and grouped into 4 categories. The 4 cateogries include: Entrance, Emphasis, Exit (The 3 E's), and Motion Paths.
Entrance effects animate object so that it enters the slide show. During the slide show view, you won't see the object until it starts to animate. Hence, if two entrance effects are added onto an object one after another, the object will disappear when the second effect starts to animate.
Emphasis effects animate object on the spot during slide show. The end result will stay there unless Auto-Reverse under the effect tab or "Rewind when done playing" under the timing tab has been checked.
Exit effects animate object so that it leaves the slide show. During the slide show view, the object will disappear from the screen based to the effect that you have added. They can be re-called by adding an Entrance effect. A fun fact is that even if you have added an Exit effect on the object, you can still add an Emphasis effect or Motion Path after the Exit effect. The object will still animate, with the exception that the animation will be hidden from the viewers.
Motion Path animate object by moving it from one position to another. There is a list of Motion Paths that you can choose from. In addition, you can draw your own motion paths, which includes Line, Curve, FreeForm and Scribble. Best way to understand how they work will be to try them out individually.