1. A method of processing graphic objects intended to form a raster pixel image, said processing comprising a process for determining an intersection order between edges of said graphic objects by evaluating corresponding edge records for a current scan line in rasterised display order and determining an edge intersection value for each said edge for a subsequent scan line, said process comprising, during processing of said edge records, the steps of: retaining a limited number of processed edge records in an unordered first buffer and progressively transferring said processed edge records to a second buffer in order, as orderable processed edge records are added to said first buffer; transferring unorderable processed edge records to a third buffer in order to'order said edge records in said third buffer; and selectively processing edge records from said second and third buffers for determining ordered intersections for a subsequent scan line.