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太让人无语了
PowerVR的KYRO/KYRO II居然敢无视？？
给LZ说说PowerVR吧--
那是一个极为重大的3D流派，并将影响今后好几年显卡的发展趋势。
larrabee吸取了PowerVR的Tile-Based分块渲染风格。
而nv与ati将可能开始进入先进的Deferred Rendering时代。尤其是fragment shader开销越来越高的时代，Deferred Rendering可以在PS之前，干掉一切不该被fragment shader处理的像素，几乎是必然的发展趋势。而且还有很有其他优势。
PowerVR known as Tile-Based Deferred Rendering (often abbreviated as TBDR). As the polygon generating program feeds triangles to the PowerVR driver it stores them in memory in triangle strip format. Unlike other architectures, polygon rendering is not performed until all polygon information has been collated for the current frame – hence rendering is deferred.
In order to render, the display is split into rectangular sections in a grid pattern. Each section is known as a tile. With each tile is associated a list of the triangles that visibly overlap that tile. Each tile is rendered in turn to produce the final image.
Tiles are rendered using a process similar to ray-casting. Rays are cast onto the triangles associated with the tile and a pixel is rendered from the triangle closest to the camera. The PowerVR hardware typically calculates the depths associated with each polygon for one tile row in 1 cycle.
The advantage of this method is that, unlike with a more traditional z-buffered rendering pipeline, work is never done determining what a polygon looks like in an area where it is obscured by other geometry. It also allows for correct rendering of partially transparent polygons independent of the order in which they are processed by the polygon producing application. (This capability was only implemented in Series 1 and 2. It has been removed since for lack of API support and cost reasons.) More importantly, as the rendering is circumscribed to a tile at a time, the whole tile can be in fast onchip memory, which is flushed to video memory before passing on to render the next tile. Under normal circumstances, each tile is visited just once per frame.
PowerVR is not the only pioneer of tile based deferred rendering, but the only one to successfully bring a TBDR solution to market. Microsoft also conceptualised the idea with their abandoned "Talisman" project. Gigapixel, a company that developed IP for tile-based deferred 3D graphics, were bought by 3Dfx, who were subsequently bought by Nvidia. Nvidia has no official plans to pursue tile-based rendering at present. |
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发表于 2008-9-23 11:19
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