“…To achieve interactive frame rates, techniques based on determining visible and occluded terrain regions 6,7 , exploiting smart data structures or vertical ray coherence for ray casting 5,23 , and incorporating level-of-detail (LOD) representations 35,36 have been proposed to speed up rendering. To reduce visual discontinuities due to LOD switching, continuous LOD techniques have been developed by several researchers 12,13,25 .…”