摘要
三维虚拟场景中,低模网格(三角面数较少的网格)在多细节层次等方面的运用对实时运算效率提升有着重要的作用。然而,给定高精度的建筑模型(高模网格),现有方法所生成的低模网格很难在达到极低简化率的同时依旧与原高模网格保持良好的视觉相似性,仍需人工调整以修正缺陷。为此提出了一个新的方法,用户仅需提供少量鲁棒的参数,就能生成具有良好视觉相似性和满足水密性、流形等良好几何特性的低模建筑网格。首先,为了从高模网格中捕获重要的几何特征,需通过逆渲染的方法对另一个新网格变形,使其与高模网格有相似的外观且仅保留大尺度的外观特征。为保持网格拓扑在变形过程中的一致性,可将高模网格体素化后的外包(The outer hull)作为被变形网格的初始化。之后,为处理变形过程中带来的相交三角形,还设计了参数自适应模型拓扑的alpha wrapping算法。通过保证变形后网格体素化后的外包和结果网格的亏格数一致,该算法能够生成变形后网格的近似网格,且保证近似网格无相交三角形、满足水密性和二流形。最后,部署了一个改进的边收缩算法将alpha wrapping算法生成的网格简化到用户的目标面数,该算法对平面上点对合并过程进行了数值优化。在一个建筑模型的数据集上测试了本文方法并将其与最流行和最先进的方法进行了比较,证明了其稳健性和有效性。
Within the domain of 3D virtual scenes,the usage of low-poly meshes(meshes comprised of few triangles)used in levels of detail play a pivotal role in improving the efficiency of real-time rendering.However,given detailed building models(high-poly meshes),it is difficult for the low-poly meshes generated by the existing methods to maintain good visual similarity with the high-poly meshes while achieving extremely low simplification rates,requiring the manual correction of defects.We proposed a novel method in which the user only needed to provide a few robust parameters to generate low-poly building meshes with good visual similarity and satisfying benign geometric properties such as watertightness and two-manifold.Firstly,new meshes were morphed by inverse rendering,enabling the capture of important geometric features from the high-poly meshes,so that they could have similar appearances to the high-poly meshes and retain only the large-scale appearance features.Additionally,to maintain the consistency of the mesh topology during the morphing process,we leveraged the outer hull of the voxelized high-poly meshes as the initialization of the new meshes.Secondly,to address the intersecting triangles that arose during the morphing process,we designed the alpha wrapping algorithm with topology-adaptive parameters.The algorithm ensured that the genus of the outer hull of the voxelized morphed meshes and the genus of the results remained the same,generating approximate meshes from the morphed meshes with no intersecting triangles,satisfying watertightness and two-manifold.Finally,an improved edge collapse algorithm was applied and generated meshes that were simplified to users’target facet count.The algorithm optimized the contraction of vertex pairs on planes.We evaluated our method’s robustness and effectiveness against a dataset of building models and compared it against popular and state-of-the-art methods.
作者
岳明宇
高希峰
毕重科
YUE Ming-yu;GAO Xi-feng;BI Chong-ke(College of Intelligence and Computing,Tianjin University,Tianjin 300350,China;LightSpeed Studios,Tencent Technology Company Limited,Bellevue WA 98004,USA)
出处
《图学学报》
CSCD
北大核心
2023年第4期764-774,共11页
Journal of Graphics
基金
国家重点研发计划项目(2021YFE0108400)
国家自然科学基金项目(62172294)。
关键词
网格简化
三角形网格
低模网格生成
细节层次
建筑模型
mesh simplification
triangle mesh
low-poly mesh generation
level of detail
building model
