Patent ID: 7425955

Claim:
A method of rendering a scan line of a graphic object image in a scan line renderer for spans of pixels lying between consecutive x-ordered edges intersecting said scan line, said method comprising the steps of: maintaining a set of depths present in the rendering of said scan line, where the set of depths is maintained using a content addressable memory, said set being maintained in depth order, and for each span, said set containing at least those depths that are active in said span, and said set being subject to removal of at least one depth at a subsequent span on said scan line where the corresponding depth is no longer active on said scan line, where said content addressable memory is addressed by at least depth, and references fill information related to graphic objects active in said span; partitioning said set of depths into those that potentially contribute to the raster data output of the current span and those depths that presently do not, said set of depths being maintained in said depth order, where said depth ordering is separately imposed on said contributing partition and said non-contributing partition; forming a combined index for each said depth in said span, each said combined index having a most significant part that indicates a corresponding one of said partitions and a least significant part indicating said separately imposed depth ordering; ordering of said combined indices to provide said partitioning and said depth ordering, said ordering of said combined indices being achieved by means of a map; associating said combined index of each said depth in said set of depths with a corresponding further depth, said further depth indicating both said partitioning by contribution and the relative ordering of depths in each partition on said span; mapping, using said map from each said further depth to said associated combined index of each depth in said set of depths; and reusing said set of depths and said map from said span to span in increasing x order, wherein said set of depths and said map maintaining an ordered state during addition and removal changes in contribution status of a depth in said set of depths.