Two methods for improving the efficiency of ray casting in solid modelling

In solid modelling based on constructive solid geometry and primitive instancing, ray casting is a very suitable technique for visualization of models on a raster display. In its present form, it is, however, too inefficient for interactive use. Two methods for improving the efficiency are given here. The first uses scan-line interval enclosures instead of box enclosures, and also bypasses non-contributing nodes during each traversal of the CSG (constructive solid geometry) tree. The second refines the image step by step by subdivision, thereby avoiding explicit computation of the intensities of many pixels of the image. The second method reduces computing time more than the first, but has the disadvantage that slivers may occasionally be lost from the image.