The invention is a method and device for producing three-dimensional objects, having a gradient of properties and multi-material objects, from powders. A method involves the selection of powders of various materials according to diameter, the successive application of layers of powder of a given thickness during the vertical displacement of a piston of a device build chamber with an object to be sintered, and the programmed selective sintering/melting of a given area in the plane of each layer. After sintering, piston is raised, unsintered powder is removed from a layer. The piston is then returned, and a layer of powder having a different diameter and being of a dissimilar material is applied and selectively sintered. When the object-sintering process is finished, the unsintered powder is removed from the build chamber, and the powders are separated according to diameter. The separated powders are returned to feed containers of device for re-use.