In current commercial feature modeling systems, support for direct
manipulation of features is not commonly available. This is partly due to
the strong reliance of such systems on constraints, but also to the lack
of speed of current constraint solvers. In this paper, an approach to the
optimization of geometric constraint solving for direct manipulation of
feature dimensions, orientation, and position is described. Details are
provided on how this approach was successfully implemented in the
Spiff feature modeling system.