针对层次式累进网格模型提出一种动态评估与动态调整的方法,为交互式变形构建最合理的数据信息。分别从细节层次和规范程度两个角度对网格模型进行评估,其中细节层次不仅包括由模型位置决定的全局细节层次,还包括由视锥原则、曲面法向量、屏幕空间几何误差和变形参与度确定的局部细节层次;规范程度衡量分为流形和定向性确定的拓扑结构规范,以及由几何元素确定的几何属性规范。依据评估结果,动态调整模块使用一系列调整操作,对模型的拓扑结构和几何属性进行修正。实验结果证明该方法能够保证良好的渲染效果,很好地保持合理的模型拓扑结构,而且在保证视觉效果和变形需求的情况下具有实时性与自适应性。

For progressive mesh models, a method of dynamic evaluation and dynamic modification is proposed to design a reasonable model structure for deformations. The evaluation specifies the levels of detail and mesh regularity and the modification changes of the topological and geometric mesh structure. The global levels of detail for all nodes of the active vertex tree are decided by the view frustum, the surface normal, the screen-space geometric error, and the deformation contribution. Topological regularity is evaluated by geometric properties. A series of modifying operations are used to correct the topological and the geometric mesh structure, where topological modifications include a global pre-construction of a mesh model and real-time adjustments on the local mesh connectivity and geometric modifications using Laplacian smoothing to change the vertex position and to eliminate deformation distortion. Guided by the evaluation results, proper modification is selected for a specified submesh, which guarantees the real-time efficiency and adaptivity. This proposed approach has been applied on progressive mesh models to prove the performance.