Reduces the data set worked on based on the specified criteria. For example, if you are deforming points on a mesh, the deformation is applied to all points. If you want the deformation to be applied only on the points with a Y position greater than zero, you can connect a Filter node and connect a graph that checks to see whether if the Y component of the position (connected in the Keep port) is greater than zero. Components that do not satisfy the criteria are omitted from the calculations and therefore not deformed.