A stereolithographic method for constructing an object from a medium capable of solidification upon exposure to synergistic stimulation (e.g. a laser beam). 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.