紋理貼圖之硬體設計

Abstract

在現今的多媒體影像應用中，三維電腦繪圖扮演了相當重要的角色。由於 紋理貼圖技術可以增加電腦合成影像的真實度，因此被廣泛地應用在現今 的三維電腦繪圖中。但是紋理貼圖運作時需要複雜的運算及龐大的記憶體 頻寬，這些因素會明顯地影響到整個繪圖系統的效能。使用專用的硬體加 速單元可以降低其對系統造成的衝擊及提升整個繪圖子系統的效能。本論 文提出了一個位於三維繪圖處理器中的紋理貼圖加速單元。此三維繪圖處 理器支援OpenGL三維繪圖程式庫。以下為此紋理貼圖單元擁有之特性：第 一，支援全部的OpenGL紋理過濾模式及全彩模式下全部的紋理函數。第二 ，使用獨立的512KB靜態隨機存取記憶體存放紋理圖樣以提昇其著色性能 及降低對整個電腦系統的影響。第三，使用者可預先載入至多六組的紋理 圖樣，以降低在切換使用不同的紋理圖樣時因為重新載入紋理而導致的延 遲。此紋理貼圖單元之工作頻率定在66MHz。在此工作頻率下，使用最簡 易之單點紋理過濾模式，每秒最多能夠完成13.2百萬個全彩像素之紋理貼 圖。而在最複雜的三元線性過濾模式下時，每秒則能完成3.47百萬個全彩 像素之紋理貼圖。 Three dimensional computer graphics plays an important role in the modernmultimedia image applications. Since the texture mapping technique canincrease the photorealism of the images synthesized by computers, it iswidely used in the modern 3D computer graphics. However, texture mappingrequires complex computation and large memory bandwidth that will affectthe system performance significantly. A hardware acceleration unit isrequired to minimize the impact on the system and increase the throughputof the graphics subsystem. The thesis proposes a texture mapping hardwarein a 3D graphics processor which supports OpenGLTM 3D graphics API. Thetexture mapping unit has the following features: first, it supports all themipmap texture filtering methods and the true color texture functions definedin OpenGLTM. Second, the hardware unit uses individual 512K SRAM to store thetexture maps in order to increase the rendering performance and minimize thesystem performance degradation. Third, users can pre-load up to six texturepatterns into the texture memory to minimize the latency for texture patternloading while switching among different textures. The operating frequency ofthe texture mapping hardware is targeted at 66MHz. Under the circumstance,it delivers maximum 13.2 million true color texture mapped pixels per secondwith the single-point texture filtering method, and 3.47 million pixels truecolor texture mapped pixels per second with the most complex trilinearfiltering method.