What Is Antialiasing?
Antialiasing is normally accomplished by multisampling, which means you use more than one pixel ("sample") from an image to determine the color of a pixel in your final image. The more samples per pixel, the smoother the resulting image.
Both PC and Xbox 360 platforms support Full Screen Antialiasing (FSAA) modes, where extra pixels are rendered to a render target and used as samples to create an antialiased final image. 4x FSAA uses four samples per pixel by rendering the scene to a render target with twice the height and width of the backbuffer. It uses the extra samples in the render target to create an antialiased final image. 2x FSAA is also common on PCs and supported by the Xbox 360.
Use the CheckDeviceMultiSampleType method to query for antialiasing support on your game machine. Also, use the MultiSampleQuality and MultiSampleType properties of the PresentationParameters to select an antialiasing mode for your backbuffer. For more information, see How To: Enable Antialiasing (Multisampling). You can set PreferMultiSampling on the GraphicsDeviceManager to true to let the GraphicsDeviceManager choose the antialiasing mode.