Voxel-Based Level-of-Detail Visualization of Isogeometric Volumes

Abstract

3D models created in Computer Aided Design (CAD) software are ubiquitous in the manufacturing industry. Preparing for analysis on them has typically been a very time-consuming process, and isogeometric analysis was therefore proposed as an alternative approach. It is desirable to be able to visualize the models during isogeometric analysis, but this is not a straightforward process due to how the CAD models are defined. A recently developed approach allows interactive visualization of these models as volumes by ray-casting. This approach ensures highly accurate renderings, but at the cost of being computationally expensive. This thesis explores ways of achieving improved performance while rendering these models, by looking at combining the isogeometric models with simplified voxelized representations. A 2D prototype was developed to experiment and test different ray-casting methods, before moving to a 3D implementation. To determine the visual accuracy of the different methods the CIEDE2000 algorithm for color difference was used to compare the results from rendering to a reference solution. Several methods have been proposed in this thesis that significantly improves the rendering performance with the results also having good visual accuracy. This includes hybrid methods that dynamically switch between isogeometric models and their voxelized representations while ensuring that samples are pixel accurate. The methods have been compared against each other in different examples, and the generated results show that some of the proposed methods are very good candidates for visualizing isogeometric volumes with increased performance.