Snap-dragging in three dimensions

A large portion of the user interface in interactive solid modeling systems is devoted to the problem of placing and orienting objects in three dimensions. In particular, many operations must be provided for selecting control points, curves and surfaces, and for translating, rotating and scaling scene components into precise relationships with other scene components. By factoring these operations carefully, it is possible to provide the desired functionality so as to reduce both the size of the user interface and the time that it takes to use it. With snap-dragging, the user takes advantage of three main elements that work together: a general-purpose gravity function, alignment objects that can be created many at a time, and smooth-motion affine transformations. Scene composition is achieved in a single perspective view using a mouse and keyboard. With 19 mouse commands, 15 keyboard commands, 5 menus of numbers, and 1 single-level menu of numerical transformations, this user interface has fewer commands and requires fewer keystrokes than the skitters and jacks technique reported earlier.