Abstract: The invention relates to a method for manufacturing a three-dimensional object, comprising locally raising the temperature of a powder using electromagnetic radiation in a heated chamber, causing the localised melting/coalescing of a layer of a predetermined thickness in order to form, after cooling, a solid polyamide layer, the method being characterised in that the powder comprises, relative to the total weight of the composition: —between 60% and 99% by weight of polyamide; —between 1% and 40% by weight of an optical and/or magnetic detection additive selected from the group formed by: pigments comprising a spinel structure containing a cation of a transition metal, the oxides of a transition metal, the sulphides of a transition metal; —between 0% and 5% by weight of a flow agent and in that the powder has: —a particle size distribution D50 of between 35 ?m and 55 ?m; and —a particle size distribution D10 of more than 15 ?m; and—a particle size distribution D90 of less than 100 ?m.