The outer most layer or boundary of an object. In PhotoModeler surfaces can be constructed from a closed loop of objects such as points, lines, and curves (a Path Surface), from a set of curves (a Lofted Surface, a Surface of Revolution, a Boundary Patch Surface, or a Swept Surface), or from a set of points (a Fit NURBS Surface). A Surface looks solid or opaque in the 3D Viewer and can be assigned Materials such as color and photo texture. See NURBS Surface.