Did you ever hear of mipmapping?
set d3d_mipmapping to 0 and you´ll may see, why it is there, if not have a look at the descrption on wikipedia or another article you can find about it...

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com