[phunge]

You're probably thinking of https://en.m.wikipedia.org/wiki/Selective_laser_sintering which is pretty widespread -- for example you can order metal parts straight off ShapeWays that are SLS!

[fudged71]

I wonder if a solar sintering machine could be made nearly as precise as an SLS machine. Maybe if you could focus the beam into a fibre optic cable and measure the intensity of light to control the path planning.