# An Animated Visualization Method for Large-Scale Unstructured Unsteady Flow
## 4 Experiment
### Mesh Simplification  
Structured simulation data can use its arrangement principles to store the flow field mesh implicitly, whereas unstructured data requires extra space to record complex, unordered, and diverse mesh cells and cell connectivity. The mesh simplification algorithm analyzes the flow field topology structure based on the surface mesh required for surface \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Data** & **Memory Needed** & **Number of Cells** & **Timesteps** & **Variables** \\ \hline Dataset 1 & 38.31 MB & 433,602 & 17 & Velocity, density, pressure, pressure coefficient \\ Dataset 2 & 14,300.5 MB & 120,649,590 & 10 & Velocity \\ Dataset 3 & 42,593.7 MB & 575,859,614 & 38 & Velocity, density, pressure, pressure coefficient \\ Dataset 4 & 42,762.9 MB & 546,400,198 & 40 & Velocity, density, pressure, pressure coefficient \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Information on experimental data. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Data** & **Original Memory** & **Memory of Selective Loading** & **Memory Ratio** \\ \hline Dataset 1 & 38.31 MB & 32.34 MB & 84.42\% \\ Dataset 2 & 14,300.5 MB & 14,300.5 MB & 100\% \\ Dataset 3 & 42,593.7 MB & 39,166.4 MB & 91.95\% \\ Dataset 4 & 42,762.9 MB & 40,690.8 MB & 95.15\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental results of load-on-demand variable-optimized memory. drawing and then replaces the original data with the minimum data required for visualization input, attaining the goal of reducing the data size. Table 3 displays the outcomes of applying the mesh simplification method and combining it with the technique described in Section 3.1 in order to optimize the memory of experimental datasets. The topology structures of dataset 2, dataset 3, and dataset 4 are primarily composed of 3D cells and the memory requirements are drastically reduced after surface extraction and linear surface division. The mesh simplification method has a greater effect when the proportion of 3D cells in the dataset is considerable, as indicated by the data in Table 4. Data preprocessing leads to a significant memory reduction even in dataset 1, which does not contain 3D cells. The combined optimization method makes use of both selective loading and mesh simplification. By employing this method, high memory reductions were achieved for all experimental datasets. It indicates that the method is highly universal for unstructured unsteady data with various composition structures. A personal computer can display larger-scale unsteady flow fields in animated form as a result of data simplification and centralized loading of the entire time step. The data processing methods are based on the VTK rendering pipeline, which also applies to the VTK-based ParaView. A new playback mode can be created by substituting the data read after data I/O with the simplified data at each time step. The outer surface extraction algorithm for 3D cells on unstructured meshes was analyzed and improved. The conventional VTK surface extraction algorithm uses cell intersection to determine whether a 2D surface is an external surface. This requires first querying which cells contain vertices within a 2D surface. The list of points that make up these cells is then intersected. It can only be referred to as an external surface if these points do not appear repeatedly in any cell. VTK reduces the overhead of seeking out cells by constructing a table of connected relations for unstructured mesh cells. However, the time it takes to build a table of connections is also costly. A hash structure was constructed to assist the lookup surfaces and reduce the number of lookups and the time cost of unsteady data processing for surface deduplication. It can significantly decrease the amount of time needed for data preprocessing, which will improve user experience. Table 4 shows the time overhead of the proposed method compared to common surface extraction techniques. Dataset 1 was not tested because it had no 3D cells.