An improved scan-line algorithm for display of CSG models

A scan-line algorithm uses a one-dimensional set operation instead of a depth comparison to find a visible surface of the object shape defined by constructive solid geometry (CSG). Interactive solid modelers employing a scan-line algorithm require considerable computing time in repeated construction and destruction of parts of the CSG object models during the design process. We discuss three steps to improve a scan-line algorithm to display the CSG models on a screen. First, changing the order of application of the partial procedures in the algorithm can improve the performance in the interactive modelers. Secondly, substituting set operations for simple manipulations of the elements in two kinds of lists reduces computing time. Finally, using the connection information at the adjoining facets drastically reduces the number of set operation executions