a stereolithographic method for constructing an object from a medium capable of solidification upon exposure to synergistic stimulation . stacked layers of solidified medium are constructed by exposing the medium to synergistic stimulation in magnitude and pre - selected pattern , such that each layer is formed with external boundaries and up and down facing surfaces as necessary . at least a portion of a layer which is neither upfacing nor downfacing is also skinned , e . g ., provided with a continuous skin formed by overlapping skin vectors or traces of the laser beam . alternatively , all intermediate or internal cross - sectional layers are provided with skin and cross - hatch . upfacing and downfacing features , and intermediate layers may be provided with a skin created by scanning in a first pass using non - consecutive skin vectors followed by scanning in at least one additional pass that completes the exposing process by filling in between the originally drawn vectors . to reduce waffling , regions of intersecting vectors at least in down - facing surfaces are determined . exposure of one or more of the respective intersecting vectors is reduced at the regions of intersection to provide downfacing features with a uniform exposure .