# Sino-InSpace: A Digital Simulation Platform for Virtual Space Environments
## 4 Design of Platform Application Modes and Case Study
### Visualization Development  
Compared with the \"Application Directly\" mode, the \"Visualization Development\" mode was proposed to develop the individualized customizable software. Figure 15 presents the core components of Sino-InSpace. The SSimAstroCore component is mainly used to provide mathematical functions and model calculations, e.g., coordinate transformation, matrix operation, orbit prediction, space environment model calculations, and so on, which are the basis of the platform. The SSim2 DView and SSim3 DView components, as the visualization engines, are responsible for the data loading and rendering. The SSimScenario component parses the scenario file and extracts different types of elements for the next step. The SSimMainApp component is the interface between the external program  
Figure 14: Blinking stereoscopic observations with the help of Nvidia 3D vision technology. The synchronous signal transmitters control the switch of two lenses of 3D glasses, while the 3D view window provides a left or right frame.  
and internal components and is the most frequently used component in \"Visualization Development\" mode. It supplies encapsulated User Interface (UI) widgets shown in Figure 11 which can be embedded in the new program conveniently. In addition to the related functions such as environment data and objects adding and time and viewpoint control, local scenario file open was also developed.  
Taking the \"Comprehensive Situation System\" in the China BeiDou Navigation Satellite System (BDS) data center as an example (Figure 16), it was developed based on Sino-InSpace in the \"Visualization Development\" mode. The offline and online location data, location device situation, BeiDou satellite situation, and map service were passed into the platform. The SSimMainApp component provides the interface for the access to these entity objects and updates their trajectory and state changes in real time. For the map service following the Web Map Service (WMS) standard, the component will obtain the image tiles under the control of Data Engine (Section 3.5). In addition, the software style was customized. Some UI widgets (time and viewpoint control tools) were invoked directly. As the platform was developed under Qt languages, a readable and declarative language, the Qt Meta-Object Language (QML) [72] is often adopted to create fluidly animated and visually appealing applications. It allows components to be easily reused and customized within a user interface.  
The entity object usually has a specific and given geometry that can be created or combined in advance. However, some invisible or changing parameters such as sensor range, communication  
Figure 16: Comprehensive situation system based on Sino-InSpace. Qt Meta-Object Language (QML) was used for the interactive operation and information display.  
Figure 15: Core component diagram of Sino-InSpace. Arrows indicate dependencies.  
link, and space environment boundary also need a visible and dynamically generated geometry. It is impossible for any visualization platform to integrate all shapes, including Sino-InSpace. Therefore, it provides the \"BaseGeometry\" class in the SSim3 DView component, which can be inherited for rendering. Any geometry drawn with a standard OpenGL language can be added to the geometric model (Figure 6) of any entity object. This function maximizes the extensibility of the platform. Figure 17 illustrates a visualization result for the Van Allen radiation belt in cooperation with the National Space Science Center (NSSC) and Chinese Academy of Sciences (CAS). The distribution and flux of the radiation belt particles were calculated by the AE8/AP8 model [(73)], which was expressed with boundary lines and colors, respectively.