The first Rapid Prototyping technique and still the most widely used. Inexpensive compared to other techniques. Uses a light-sensitive liquid polymer. Requires post-curing since laser is not of high enough power to completely cure. Long-term curing can lead to warping.
Parts are quite brittle and have a tacky surface.
Support structures are typically required. Uncured material can be toxic. Ventilation is a must. A vat of photosensitive resin contains a vertically-moving platform. A laser beam traces out the shape of each layer and hardens the photosensitive resin .