Yep it is done by DirectX. The keyword is texture sampler. The texture sampler defines how a texture gets sampled on the GPU. There are different modes of interpolation for each sampling. Common modes are Point (Single pixels, no interpolation), Linear (Linear interpolation between pixels) and Anisoptric (directional depending interpolation).


Not directly, but a correct sampler used in the shader. Gamestudio allows you to swap between linear and point interpolation without shader usage:
http://www.conitec.net/beta/aentity-nofilter.htm