Animating Geometry?

[richtann]

OKay this is probably a really basic question but here goes. How do you animate vertices and faces if the structure of them changes during the course of the animation?

Example, animating a knife cutting through paper. If you don;t want the join in the the paper visible before hand i guess you need to split the vertices one at time to show split in the paper gradually progressing along the cut.

This doesn;t seem possible as when i alter/split the vertices or the faces the animation is lost. If the vertices are in the original non-cut paper, the edges are visible.

Hope that makes sense, i must be missing something really simple. How does everyone else deal with thi sort of problem?

Thanks in advance for any reponses

[joojaa]

first split the geometry up set the normals locked so they are consistent if necessary, then keyframe the edge vertices or use a indirect skin to control them such as a blend shape or latices.