A method for forming a three-dimensional article by powder bed fusion, comprising the steps of: (a) distributing a first layer of a powdered medium over a powder bed; (b) heating the first layer of the powdered medium distributed over said powder bed to a temperature below a melting point of the powdered medium; (c) projecting an image (66, 74) of a first cross-sectional layer of the three-dimensional article on the first layer of the powdered medium distributed over said powder bed, wherein a projected image (72, 78) of the first cross-sectional layer is created by spatial light modulation of a first laser beam and projection of a resulting spatially light modulated laser beam through a first optical path onto the first layer of the powdered medium, said spatially light modulated laser beam having sufficient energy to fuse that portion of the powdered medium in locations in the powder bed corresponding to said image (66, 74) of the first cross-sectional layer of the three-dimensional article so as to form a fused portion of the first layer of said powdered medium having a shape corresponding to said image (66, 74) of the first cross-sectional layer of the three-dimensional article; (d) distributing a second layer of the powdered medium over the first layer of the powdered medium, and repeating steps (b) and (c) for the second layer and an image of a second cross-sectional layer of the three-dimensional article, respectively, so as to form a fused portion of the second layer of said powdered medium having a shape corresponding to said image of the second cross-sectional layer of the three-dimensional article; and (e) further repeating step (d) for additional layers of the powdered medium, each individual one of said additional layers being distributed over an immediately preceding layer of the powdered medium, additional fused portions of respective ones of the additional layers, and additional images of respective additional cross-sectional layer of the three-dimensional article, so as to form the three-dimensional article, wherein during forming of the three-dimensional article, gray levels of portions of the respective images (66, 74) of the cross-sectional layers of the three-dimensional article are adjusted according to measured power or temperature distributions of the respective projected images (72, 78) monitored through one or more imaging devices during the projecting of the respective images (66, 74) and fusing of the powdered medium. (a) distributing a first layer of a powdered medium over a powder bed; (b) heating the first layer of the powdered medium distributed over said powder bed to a temperature below a melting point of the powdered medium; (c) projecting an image (66, 74) of a first cross-sectional layer of the three-dimensional article on the first layer of the powdered medium distributed over said powder bed, wherein a projected image (72, 78) of the first cross-sectional layer is created by spatial light modulation of a first laser beam and projection of a resulting spatially light modulated laser beam through a first optical path onto the first layer of the powdered medium, said spatially light modulated laser beam having sufficient energy to fuse that portion of the powdered medium in locations in the powder bed corresponding to said image (66, 74) of the first cross-sectional layer of the three-dimensional article so as to form a fused portion of the first layer of said powdered medium having a shape corresponding to said image (66, 74) of the first cross-sectional layer of the three-dimensional article; (d) distributing a second layer of the powdered medium over the first layer of the powdered medium, and repeating steps (b) and (c) for the second layer and an image of a second cross-sectional layer of the three-dimensional article, respectively, so as to form a fused portion of the second layer of said powdered medium having a shape corresponding to said image of the second cross-sectional layer of the three-dimensional article; and (e) further repeating step (d) for additional layers of the powdered medium, each individual one of said additional layers being distributed over an immediately preceding layer of the powdered medium, additional fused portions of respective ones of the additional layers, and additional images of respective additional cross-sectional layer of the three-dimensional article, so as to form the three-dimensional article,