A Scan Conversion Algorithm Using Quad-Tree Representation of dZ Buffer.

This paper proposes an extension of the Z buffer or dZ buffer that stores not only the Z component but also the normal vector of a visible polygon at the sampling point. While the conventional Z buffer algorithm is based on a zeroth-order approximation of a visible polygon, the dZ buffer is considered as a first-order approximation. As a result, the dZ buffer can approximate a surface by fewer sampling points. A quad-tree based internal representation of the dZ buffer and scan conversion algorithm has been proposed using the representation. The proposed algorithm uses memory in proportion to the complexity of the generated image while the Z buffer uses memory in proportion to the image size. While the algorithm allows an incremental update of the dZ buffer as similarly to the Z buffer, anti-alias processing is possible by controlling oversampling on demand. The algorithm can be implemented using recursive procedure calls including simple overlapping detection of triangles and rectangles. The algorithm is implemented and evaluated on a UNIX workstation and the result shows better figures in both conversion time and memory requirement. [ABSTRACT FROM AUTHOR]