Mobile 3D Graphics SoC

Abstract

A 3D graphics pipeline has geometry operations for computing the attributes of vertices of polygons, and rendering operations for filling colors inside the polygons. The geometry stage generates vertex data from primitive input vertex attributes using transformation, lighting, and perspective projection. The rendering stage draws pixels from the vertex data computed in the geometry stage. First, vertex data are transformed into sets of 2D triangles using interpolation to calculate edge coordinates for each polygon. Then every pixel is rendered by shading and texture mapping. Alpha blending for translucent objects and depth comparison for hidden surface removal are performed during the rendering stage.The geometry operation is computation-intensive, and the rendering operation is data-intensive as well computation-intensive. To relieve bottlenecks, 3D graphics hardware has been evolving using fast, parallel datapaths such as multicore vector processors with 3D graphics-optimized memory systems [1,2].Mobile devices have limitations imposed by their power supply, their computational power, physical dimensions, and input devices. The fundamental problem is that mobile devices are powered by batteries.With regard to the hardware, the key issue to achieve good graphics performance and low power consumption is to reduce the internal data transactions between graphics-processing unit (GPU) and memory. Many researchers have focused on how to reduce or how to compress data transactions. As a result, various mobile graphics hardware approaches have been reported, including tile-based rendering [3], specialized embedded DRAM [4], and compression algorithms. They have employed various low-power techniques such as clock gating [5], power-down schemes, and voltage/ frequency scaling [5].With regard to the software, standard application programming interfaces (APIs) for embedded systems have been released: OpenGL-ES [6] and Microsoft Direct3D-Mobile [7]. The first is a subset of desktop OpenGL and adopts optimizations and Mobile 3D Graphics SoC: From Algorithm to Chip