1. A computer-implemented method of generating slices of a three-dimensional (3D) body in a 3D solid modeling application, comprising: acquiring, in a computer, the 3D body in the 3D solid modeling application, wherein the 3D body comprises a modeling assembly having multiple 3D parts; specifying whether each of the multiple 3D parts in the assembly participates in a single slice model representation and is included in a slice operation or does not participate in the simple slice model representation and is hidden in the single slice model representation; generating, in the computer in the 3D solid modeling application on the 3D body, one or more slice geometries, wherein each of the one or more slice geometries defines a respective slice cutting surface; based on, and for each of the one or more slice geometries, slicing, in the computer in the 3D solid modeling application, the 3D body through the surface of the 3D body, to create one or more respective zero-depth slices, wherein each zero-depth slice comprises an outline of the 3D body where it intersects with the respective slice cutting surface; and generating, in the computer, the single slice model representation that comprises a simultaneous representation of all of the one or more respective zero-depth slices; wherein: if a first 3D part of the multiple 3D parts does not participate in the single slice model representation, the first 3D part is displayed in an original form of the first 3D part in the 3D solid modeling application and is hidden from display in the single slice model representation; and if the first 3D part participates in the single slice model representation, a zero-depth representation of the first 3D part is displayed in the single slice model representation of the 3D body.