1. A method for designing, on a display device, a geometric shape, comprising the steps of: on a display device, displaying an initial set of similarly structured model exemplars, each exemplar including a first portion and a second portion; selecting a plurality of the model exemplars from the initial set of similarly structured model exemplars to apply to a model mix; mixing the plurality of selected model exemplars to form a morphable model whose shape is defined by an average of the shapes of the selected model exemplars, said morphable model including a first portion and a second portion; on the display device, providing a plurality of selectable feature for manipulating the second portion of the morphable model, wherein a user can select a particular selectable feature to manipulate only that feature of the morphable model by moving a pointer on the feature on the display, and wherein selecting the particular selectable feature causes the display to display a cluster of points on the morphable model that define a space of the selected feature that includes the position of the selected feature for all of the exemplars in the model mix; and applying at least one constraint of the selected selectable feature to the morphable model to update both the first portion and the second portion of the morphable model into a new geometric shape design.