To avoid aliasing caused by a 2D bump map, go to the bump map's Coordinates rollout. Set Blur to be in the range 0.3 to 0.6, and increase Blur Offset to be greater than 0.0. The default Blur and Blur Offset values work well for mapping other material components, but for bump mapping, lower Blur and higher Blur Offset values give better results
If you render a bump-mapped material and notice aliasing in the highlights, try turning on supersampling and rendering again
Filtering group
Filtering options let you select the method of pixel averaging used in antialiasing the bitmap.
Pyramidal: Requires less memory and is adequate for most purposes.
Summed Area: Requires much more memory, but yields generally superior results.
None: Turns off filtering.