各向异性滤波器的硬件实现

在计算机图形学中,通常采用各项同性滤波器逼近异性滤波器以减少纹理映射中发生纹理走样,逼近算法中实现MIP-MAP层级包含计算覆盖区域边长以及求对数等操作,用二次逼近或者Cordic算法等实现时电路较大.为了易于算法的硬件实现,提出用线性逼近计算覆盖区域边长和对数的算法.该算法用一次移位和一次加法实现覆盖区域边长计算,用一次加法实现对数计算,降低了硬件实现成本.在Xilinx的ZC706开发板上实现了文中算法,实验结果表明,该算法所计算MIP-MAP的层级数与原算法的计算误差绝对值为1的概率为7%.

Hardware Implementation of an Anisotropic Texture Filter

In order to decrease the texture aliasing during texture mapping,one of methods is to approximate aniso-tropic filtering by isotropic filtering in computer graphics field.In such an approximation,MIP-MAP layer could be obtained using footprint and logarithm,whose implementations cause larger size of the circuits in Cordic or quadratic approximation.In this paper,a linear approximation to calculate footprint and logarithm is presented to simplify their circuits and footprint calculation with one adder and one shifter and logarithm with one adder were implemented.The absolute value of error of MIP-MAP layers between the approximation and origin is less than 7%.The approximate anisotropic filtering proposed in this paper was validated on Xilinx ZC706 board.