Real - Time Continuous Level - of - Detail Terrain Rendering With Nested Splitting Space

Real-time visualization of large-scale terrain models requires complex continuous level-of-detail (LOD) schemes to reduce the prohibitively large geometry complexity of natural terrain to an acceptable level while maintaining high image quality. This paper presents new algorithms and data structures to solve this problem. Our solution centers on computing independent per-vertex error bounds, which we call nested splitting space, for vertices in the height field according to screen-space error metrics and vertex dependence hierarchy. Based on this, a framework for circular array based, frame-coherent mesh refinement and reduction is devised. A simple mechanism to support vertex morphing requiring zero storage overhead is proposed, and methods for procedural generation of error bounds are given, providing support for real-time on-demand procedural details generation. The algorithm accomplishes LOD updates in time proportional to the number of LOD changes needed for each frame. In our sample implementation, updating the mesh takes less than onetenth of the time spent on processing and rendering the mesh by the graphics hardware. The contributions of this paper are twofold: First, the idea of computing independent per-vertex error bounds, which can also be utilized by other LOD algorithms, is presented; Secondly, accompanying schemes of frame-coherence optimization, vertex morphing support, and procedural error bounds generation for continuous LOD rendering of terrain, which outperform existing methods in terms of efficiency, storage requirement, supported features and ease of implementation, are proposed.