Multisampling is an antialiasing technique directly supported by DirectX and obviously by XNA. The problem of aliasing occurs when you draw a line on a monitor with low resolution. In that cases you see a stair step when approximating a line by a matrix of pixels. Multisampling use neighbouring pixels (called samples) to calculate the final color of a pixel.
You can enable multisampling in XNA in this simple way:
graphics.PreferMultiSampling = true;
Then you should also specify two options.
The type is an enumerator (MultiSampleType) that represent the number of samples to use in multisampling. The quality is an integer that represent the quality level. This value is always set to zero. Before to set the type of multisampling you should always check if the graphic adapter support it using the method adapter.CheckDeviceMultiSampleType()
graphics.PreparingDeviceSettings += new EventHandler<PreparingDeviceSettingsEventArgs>((sender, e) =>
{
PresentationParameters parameters = e.GraphicsDeviceInformation.PresentationParameters;
parameters.MultiSampleQuality = 0;
#if XBOX
pp.MultiSampleType = MultiSampleType.FourSamples;
return;
#else
int quality;
GraphicsAdapter adapter = e.GraphicsDeviceInformation.Adapter;
SurfaceFormat format = adapter.CurrentDisplayMode.Format;
if (adapter.CheckDeviceMultiSampleType(DeviceType.Hardware, format, false, MultiSampleType.FourSamples, out quality))
{
parameters.MultiSampleType = MultiSampleType.FourSamples;
}
else if (adapter.CheckDeviceMultiSampleType(DeviceType.Hardware, format, false, MultiSampleType.TwoSamples, out quality))
{
parameters.MultiSampleType = MultiSampleType.TwoSamples;
}
});
For more information:
http://en.wikipedia.org/wiki/Multisample_anti-aliasing
http://msdn.microsoft.com/en-us/library/bb975403.aspx