  Blocking and shadowing is one of the key effects in designing and evaluating
a thermal central receiver solar tower plant. Therefore it is convenient to
develop efficient algorithms to compute the area of an heliostat blocked or
shadowed by the rest of the field. In this paper we explore the possibility of
using very efficient clipping algorithms developed for the video game and
imaging industry to compute the blocking and shadowing efficiency of a solar
thermal plant layout. We propose an algorithm valid for arbitrary position,
orientation and size of the heliostats. This algorithm turns out to be very
accurate, free of assumptions and fast. We show the feasibility of the use of
this algorithm to the optimization of a solar plant by studying a couple of
examples in detail.
