One of the possibilities of using a script link that acts on frame changes is the ability to modify the actual mesh either by changing the vertices of a
Mesh object or by associating a completely different mesh with a Blender object. This is not possible when using IPOs as these are limited to shape keys that interpolate between predefined shapes with the same mesh topology (the same number of vertices connected in the same way). The same is true for curves and text objects.
One application of that technique is to implement a
counter object that will display the number of seconds since the start of the animation. This is accomplished by changing the text of a
Text3d object by way of its