Key Technologies Of Three-Dimensional Visualization For Eletronic Sand Table

As an important stereoscopic display device, electronic sand table is widely used in military simulation, architectural display, engineering transforrmation, agricultural planning and many other fields. In this dissertation, the auto-stereoscopic display and super multi-view light field display is used as electronic sand table display device, and the application of ray tracing technology and rasterization graphics technology is used to realize scientific visualization simulation and visualization of three-dimensional electronic sand table display effect. Key technologies of 3D visualization of electronic sand table include three parts: terrain and vector line single-viewpoint high speed rendering technology, super multi-view stereo visual rendering technology and electronic sand visualization simulation based on ray tracing technology.The main research contents and innovations of this dissertation are as follows:(1) Large terrain and vector line single-viewpoint high speed rendering technology of electronic sand tableKey point 1: The real-time display of large terrain is the main content of electronic sand table display. We propose a high-speed raster rendering algorithm based on GPU and a large terrain rendering algorithm based on ray tracing. In the first method,elevation images are compressed, encoded, decompressed in GPU, and visualized in large terrain based on viewpoint positions. At 1920×1080 resolution, the average rendering frame rate is 800 frames per second. This method is suitable for the terrain display of stereoscopic display below eight viewpoints. In the second approach, ray tracing algorithm is applied for performing efficient collision detection for large terrain,by use of the acceleration structure of Mipmap.The average rendering frame rate is around 50 frames at high resolution.Key point 2: Vector line is an important geographical information symbol, which is used to show roads, rivers and so on. The real-time display of vector lines in 3D scenes always shows such problems as disconnection, aliasing and dangling. The RBSC algorithm solves these problems. The RBSC algorithm uses the rasterization algorithm provides depth information and ray tracing algorithm combined, which greatly reduces the computational complexity of collision detection in the light, to ensure no distortion and to achieve efficient real-time rendering.(2) Super multi-view stereo visual rendering technologyKey point 3: The view frustum of electronic sand table is different from the ordinary stereoscopic display. An ordinary stereoscopic display is placed perpendicular to the ground, and people stand in front of it to observe, so the shear of view frustum is only on horizontal. The view frustum shear of electronic sand table is not only in the horizontal direction, but also in the vertical direction. We deduce the model view matrix and the shear projection matrix of each view point frustum of the electronic sand table.This will ensure that the virtual space and reality meet the proportion of 1:1 relationship.Key point 4: Scene graph in the 3D engine generally is used for scene organization.To be compatible with the original 3D engine, we design a general scene graph parallel computing framework, and implemented it by using of OSG and OpenCL. The 2D+D image can be acquired from the OSG engine, and the parallel computation of DIBR is implemented in the OSG-OpenCL framework. DIBR parallel computing technology can generate any view point image in real time, without the influence of view point number. Due to the limited amount of information provided by 2D+D, DIBR technology can not render stereoscopic images with large viewing angle.Key point 5: The viewpoints of multi-view integrated imaging electronic sand table can reach 90x 90, and the original technology is difficult to achieve real-time rendering.DIBR technology is difficult to achieve large perspective stereo rendering. By using ray tracing technology to change the starting position and direction of rays, and with the acceleration technology of SBVH ray-object collision, the real-time rendering of the multi-view integrated imaging system has been achieved.(3) Visual simulation technology of display effect of electronic sand table based on ray tracing techniqueKey point 6: Ray tracing technology not only can realize electronic sand table content production, but also can use for display quality visualization simulation of electronic sand table stereoscopic display equipment. We make a visual simulation of auto-stereoscopic displays, and light field stereoscopic displays. In this dissertation, the intensity distribution of the parallax barrier stereoscopic display is analyzed, and the crosstalk of each viewpoint is studied. We have realized the real-time visualization simulation of the light field electronic sand table and stereoscopic display, and the researchers have seen the results of imaging. Optical field visualization simulation can not only provide visual display effect, but also can be combined with SSIM index. It can provide objective evaluation index for display quality of light field stereoscopic display.