A direct manipulation user interface provides a user with a means to interact with control points associated with smart objects to create and modify complex 3D graphic objects. The direct manipulation user interface includes a precision control mechanism that enables a user to specify precise measurements for a transformation through the user's interaction with a control point. The direct manipulation user interface also includes a history bar that enables a user to scroll back to a previous stage in the design process and to undo a sequence of transformations through the user's interaction with the history bar.