Research On Hardware-accelerated CAD Displaying Technique

In the past, CAD developers can't display photo-realistic images while keeping good computer-human interaction, and have to make trade-off between them. With the rapid development of graphics hardware, we can now achieve both and are getting closer to real-time photo-realistic images in CAD rendering.The improvements of computer graphics hardware bring not only faster rendering speed, but also more functions. In this article, the author introduces some new techniques in hardware-accelerated rendering, and applies them in CAD displaying. Those new techniques bring CAD more realistic images, more kinds of objects to display, and more other functions. In the first chapter, the author introduces some hardware-accelerated techniques using OpenGL extensions and hardware programmable shading language which are the foundations of this dissertation.Per-pixel lighting is a major advance to photo-realistic images. It gives more details and more accurate lighting effects than conventional per-vertex lighting. With the help of pixel level programming, we can computer lighting per pixel real-time. In the second chapter, the author explained how to implement per-pixel lighting in graphics hardware. Then, the author purposes an algorithm of generating soft shadows for area light with hardware-acceleration. The algorithm is as follows. Based on an algorithm of soft shadows for linear light, the author purposed an algorithm of soft shadows for area light by area approximation. This new method solved the artifact of linear visibility transition in the algorithm for linear light, and can generate convincing soft shadows for area light.Due to hardware improvements, silhouette and hatch can be generated and displayed real-time. In the first section of chapter 3, the author introduces three different kinds of method for displaying silhouette, and compares the results of the three methods. In the second section, the author purposed a method of generating hatch area. This method use stencil buffer to generate the hatch area, then apply a hatch texture on the area. With this method, we can display hatch real-time. Then the author purposes a method of generating antialiased hatch real-time using eg language.Two Algorithms for collision detection based on z-buffer is purposed next. First, the author purposes an algorithm using single z-buffer to detection collisions between simple objects. Then the author enhances it using multiple z-buffers. The user may use simple single z-buffer to detect collision inaccurate or use multiple z-buffers to detect precisely. Both are suitable for real-time applications.Previous algorithms may result in conflicts in hardware resource. The author discusses how to modify conventional rendering path to accommodate all the effects and functions while keeping maximum performance.And the author concludes with conclusions and future work.