Method and apparatus for approximating nonlinear functions in a graphics system

摘要

A method and apparatus for approximating exponential and other nonlinear functions in a graphics system is accomplished using a linear interpolator adapted to receive a graphics primitive that includes vertex values for a parameter at each vertex of the graphics primitive. The linear interpolator determines a linear interpolation value for the parameter at a selected pixel within the primitive based on the vertex values. The linear interpolation value is then used to generate a first index and a fractional value, where the fractional value is the difference between the linear interpolation value and the first index. The first index is then incremented to produce a second index. The first and second indexes are then applied to a memory block that stores a discrete sampling of a nonlinear function corresponding to the parameter. The first index and the second index correspond to sample points of the nonlinear function, and the memory block provides a first sample and a second sample of the nonlinear function in response to the first and second indexes. An arithmetic unit then combines the first and second samples using the fractional value to determine a value for the parameter at the selected pixel.