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

Solid modelling systems, which have been introduced during the last few years, provide unambiguous and informationally complete representation of rigid solid objects. A constructive-solid-geometry (CSG) scheme combined with a primitive-instancing scheme to represent primitive objects is a very elegant and efficient combination for representing solid objects. Ray casting, also called ray tracing, is a general technique for rendering shaded images on a raster display. The ray-casting procedure in its original form is straightforward but very inefficient. The present investigation is concerned with two methods for improving the efficiency of the procedure. In the given modification corresponding to the first method, a 'ray intersects box' test is reduced to a 'point in scan-line interval' test. The second method is based on the notion of coherence in the intensities of neighboring pixels in the image.