周英，牛露佳，王占刚，等.工程地质三维岩性网格模型体绘制的边界平滑方法［J］.河南理工大学学报（自然科学版），2024，43（2）：77-87.

ZHOU Y，NIU L J，WANG Z G，et al.Boundary smoothing for volume rendering of 3D lithology grid model in engineering geology［J］.Journal of Henan Polytechnic University（Natural Science），2024，43（2）：77-87.

工程地质三维岩性网格模型体绘制的边界平滑方法

周英1，牛露佳1，王占刚1，张曦2，许钊上3

1.中国矿业大学（北京） 地球科学与测绘工程学院，北京 100083；2.北京市勘察设计研究院有限公司，北京 100038；3.河北雄安新区管理委员会 规划建设局，河北 保定 072750

摘要:  目的 为了解决工程地质三维岩性网格模型体绘制过程中岩性属性在岩层分界处非连续过渡而产生锯齿的问题，方法 提出一种三维岩性网格模型细分的边界线性平滑方法。基于岩层水平连续和纵向上空间叠置关系下老上新的特点，借鉴相邻钻孔岩层连接地质界面的思路，将岩性网格组织为横向上规则划分、纵向上记录岩层段顶底高程值的形式，类似规则分布的虚拟孔（称为垂直柱Pillar），并基于此种形式在光线投射过程中利用采样点周围4个岩层段形成属性计算单元，再定义相邻柱Pillar上岩层连接规则和16种空间单元细分模板，实现模型空间内任意点的岩性属性线性计算。结果 通过WebGL2.0在GPU中实现与验证，得出可以明显平滑纵向上的岩层分界，解决了体绘制岩性边界的锯齿问题，最终实现采样点岩性属性的计算并得到平滑后的效果。结论 结果表明，将岩层特点与体绘制光线投射算法空间采样过程结合，针对水平连续假设的工程地质岩层具有较好的平滑效果，可为工程地质岩性网格可视化的抗锯齿处理提供一种新思路。但是，因岩层间没有明确清晰的层序关系，因此不能处理含断层的模型，也不能处理大倾角岩层横向不连通的情况。

关键词: 三维岩性网格；光线投射；锯齿；体绘制；平滑

doi:10.16186/j.cnki.1673-9787.2021110123

基金项目:国家自然科学基金资助项目（41672326）

收稿日期: 2022/11/28

修回日期: 2023/02/21

出版日期:2024/03/25

Boundary smoothing for volume rendering of 3D lithology grid model in engineering geology

ZHOU Ying1，NIU Lujia1，WANG Zhangang1，ZHANG Xi2，XU Zhaoshang3

1.College of Geoscience and Surveying Engineering，China University of Mining & Technology （Beijing），Beijing 100083，China；2.BGI Engineering Consultants Ltd.，Beijing 100038，China；3.Planning and Construction Bureau，Hebei Xiongan New Area Management Committee，Baoding 072750，Hebei，China

Abstract: Objectives In order to solve the sawtooth problem caused by the discontinuous transition of lithologic attribute at the boundary of rock strata in the volume rendering process of 3D lithology grid model in engineering geology， Methods a boundary linear smoothing method of 3D lithology grid model subdivision is proposed.According to the characteristics of horizontal continuity of rock strata and the rationality of spatial superposition relationship in vertical direction，and drawing on the idea of connecting adjacent borehole rock formations to the geological interfaces，the lithologic grid is organized into a form of regular division in horizontal direction and vertical recording of top and bottom elevation values of rock segments.Similar to a regularly distributed virtual hole（called a vertical column pillar）.Based on this kind of organization form，in the process of light projection，four strata formation around the sampling point are used to form attribute calculation units，and define the strata connection rules and 16 subdivision templates.Linear calculation of lithological properties at any point in the model space is realized. Results Through the implementation and verification of WebGL2.0 in GPU，it is concluded that the rock vertical boundary on the longitudinal direction can be significantly smoothed，which solves the sawtooth problem in volume drawing of rock boundaries.Finally，the calculation of the lithologic attribute at the sampling point is realized and the effect after smoothing is obtained. Conclusions The results show that the characteristics of the rock strata are combined with the spatial sampling process of the volume drawing ray projection algorithm，and the smoothing effect is good for the engineering geological rock strata with the assumption of horizontal continuity，and provide a new idea for the visualization of lithology grid in engineering geology.However，because there is no clear sequence relationship between rock strata，the belt fault model cannot be processed，nor can the transverse disconnection of large dip rock strata be dealt with.

Key words:3D lithology grid；ray casting；aliasing problem；volume rendering；smooth