Flex Modifier
Flex is a powerful yet simple modifier that allows your object to be effected by forces and deflectors.
Below is a plane that has the flex modifier applied to it. A wind force is then assigned to the flex modifier, the plane is now blown about in the wind, much like a flag. Vertice weights control the rigidity of the object, a value of 1.0 will cause the vertice not to move at all, and vertices with zero values will experience the full effect of the force.
Vertice weights can be painted using a brush that is constrained to the object's surface, various brush options make fine tuning fast and simple.
The simulation is played back in the timeline automatically and without keys. Very dense meshes require more computer resources and may take longer to simulate. The plane had 12x12 segments and play back was over 150fps (frames per second).
Some example uses of the flex modifier include simple cloth effects, water, grass blowing in the wind etc.