Huamin Qu Feng Qiu Nan Zhang 0011 Arie E. Kaufman Ming Wan Ray Tracing Height Fields. 202-209 2003 conf/cgi/2003 Computer Graphics International http://csdl.computer.org/comp/proceedings/cgi/2003/1946/00/19460202abs.htm db/conf/cgi/cgi2003.html#QuQZKW03