A method for defining a color gradient across a region in a display space that includes defining a bi-cubic patch enclosing the region. The bi-cubic patch includes four corners having a color associated therewith and four curves connecting pairs of the corners forming a closed loop. The four curves define...http://www.google.ca/patents/US6313840?utm_source=gb-gplus-sharePatent US6313840 - Smooth shading of objects on display devices
