title: Massively Parallel Editing and Post-Processing of Unstructured Tetrahedral Meshes for Virtual Prototyping
Creators: name: Ströter, Daniel
Publisher: name: UNSPECIFIED
Year: 2024

description: Today, many tasks in industrial product development rely on virtual prototyping to reduce development time and resource costs.
 Although virtual prototyping provides significant simplification of product development through the use of computer-aided design and computer-aided engineering, it remains a laborious and time consuming process that involves a number of complex steps.
 Typically, product development teams optimize their prototypes for many design goals, e.g., economical use of material and stability under forces, which demands many iterations of virtual prototyping.
 Therefore, methods for the acceleration and shortening of virtual prototyping processes are important technological advances.
 
 This thesis presents massively parallel algorithms that exploit the impressive aggregated processing power of present-day general purpose graphics processing units to accelerate and shorten virtual prototyping.
 As virtual prototyping oftentimes involves the generation, optimization and adaptation of high-resolution volumetric meshes for numerical simulation, this thesis focuses on efficient processing of volumetric meshes.
 Unstructured tetrahedral meshes are a commonly used type of volumetric meshes, because they provide robust meshing and tetrahedra allow for good discretized approximation of surface features.
 Therefore, this thesis narrows its scope to unstructured tetrahedral meshes.
 
 In virtual prototyping, a number of properties of the tetrahedral mesh concerns the success of a numerical simulation.
 Important properties are the resolution of the mesh and the shape quality of the tetrahedral elements.
 Consequently, the optimization and re-meshing of tetrahedral meshes are common tasks in virtual prototyping.
 This thesis investigates parallelization strategies for tetrahedral mesh editing operations that are fundamental for mesh optimization and re-meshing.
 In addition, the robustness of the presented methods is a research objective, because successful acceleration of virtual prototyping is only achieved, if the presented methods function properly and produce meshes that are suitable for downstream numerical simulation.
 
 One of the primary overheads in virtual prototyping is that new prototype designs demand new discretization of boundary representations to a volumetric mesh.
 For this reason, virtual prototyping processes can be significantly shortened by methods for avoiding the repeated modeling of the prototype's boundary representations and subsequent mesh generation.
 In order to extend the facilities of shorter virtual prototyping iterations, this thesis explores user-interactive methods for directly editing the tetrahedral mesh without adjusting the boundary representations in a computer-aided design environment.
 The fast run time performance of massively parallel processing provides promising potential to achieve editing of high-resolution meshes at interactive rates. 
 
 Every virtual prototyping process requires a method that allows the development team the visual analysis of the simulation results. 
 In the visual analysis step, the development team typically applies post-processing to the mesh and its annotated simulation results.
 Since accurate numerical simulations might require high-resolution meshes, the use of graphics processing units is common for post-processing. 
 For post-processing volumetric meshes, it is important to visualize the inner structures of the mesh to enable a complete analysis of the prototype.
 A common method for post-processing volumetric meshes is direct volume rendering.
 The direct volume rendering of high-resolution meshes requires comprehensive acceleration data structures for fast spatial search of mesh elements, which can lead to large memory consumption.
 Therefore, this thesis investigates memory-efficient post-processing of unstructured tetrahedral meshes for better management of the available memory capacity.
 
 This thesis presents a multitude of contributions for faster virtual prototyping.
 It presents conflict detection methods to determine dense sub-meshes for massively parallel edge/face flips and re-meshing.
 In addition, this thesis contributes a robust massively parallel method to relocate mesh vertices for first-order optimization methods. 
 With the use of the presented methods, optimization and re-meshing of unstructured tetrahedral meshes can be accelerated by one or two orders of magnitude.
 For shortening virtual prototyping, this thesis presents user-interactive editing by user-selected face groups as well as deformation control to edit unstructured tetrahedral meshes. 
 Due to massively parallel processing, these methods enable interactive mesh editing.
 The mesh editing includes measures for producing tetrahedral meshes of sufficient quality for downstream numerical simulations. 
 For post-processing of unstructured tetrahedral meshes, this thesis presents a memory-efficient spatial data structure along with a method to coarsen meshes for direct volume rendering.
 The spatial data structure enables control over memory consumption by a tuning parameter.
 The coarsening can reduce high-resolution tetrahedral meshes to a quarter of the initial size while well-preserving most visual features.