Coarse-Z Filter:降低深度带宽的图形流水单元

Coarse-Z Filter:a Graphics Pipeline Unit to Reduce Depth Bandwidth

提出Coarse-Z Filter（CZF）图形流水单元,在像素级深度测试前进行Tile级深度测试,以减少读Z-Buffer的次数,从而有效地降低图形流水线的带宽.CZF提供单缓存和双缓存2种模式,前者由一个低分辨率过滤缓存组成,存储扫描转换后Tile内所有采样点的最大深度值;后者增加了一个辅助缓存和掩码位平面,以获得更高的剔除效率.测试结果表明,在当前渐趋复杂的场景中,使用CZF可降低30%～40%的带宽.

We proposed a graphics pipeline unit, namely Coarse-Z filter （CZF）, for tile-level depth culling prior to per-pixel test, to reduce depth reading and thus reduce the pipeline bandwidth. CZF provides two modes, namely Single CZF, which employs a low-resolution Filter Buffer storing the maximum depth of a scan-converted tile; and Double CZF, which adds an auxiliary buffer and a bit mask plane to gain a higher culling ratio. Test results shows that CZF can reduce up to 30% -40% pipeline bandwidth in today＇s scenes being more complex.