A HIDDEN-LINE ALGORITHM USING PICTURE SUBDIVISION TECHNIQUE

An algorithm is presented for removing hidden lines for isometric or perspective projections of three-dimensional objects. Lines connecting nodal points are first retrieved from the model to be displayed. Instead of testing against the entire population of the projected planes to see if a line is totally or partially hidden, only potential covering planes belonging to a certain neighborhood of the line are considered. Shifting from a global view to a local view, the efficiency of the algorithm is much improved; in fact the CPU time required for a plot increases only linearly with the number of planes present in the model. Improvement can also be found in the hidden-line elimination process (search for intersection and hidden portions) where classifications and case subdivisions are generalized and combined, and calculations for their determinations are also simplified. Examples of various degrees of complexity are given.