MoonWorks-docs/content/Graphics/Resources/Sampler.md

title	date	weight
Sampler	2021-01-25T20:48:35-08:00	3

You might be familiar with the concept of "sampling" in music, where artists take a small segment of recorded music and recontextualize it in another work. Similarly, in graphics applications, sampling refers to the process of looking up segments of texture information in a shader so the data can be used.

Samplers tell the renderer how upscaling or downscaling scenarios should be filtered. They can also cause the texture to repeat or mirror itself, among other possibilities.

To create a sampler, define a SamplerState struct:

var mySamplerState = new SamplerState
{
    MinFilter = Filter.Linear,
    MagFilter = Filter.Linear,
    MipmapMode = SamplerMipmapMode.Linear,
    AddressModeU = SamplerAddressMode.Repeat,
    AddressModeV = SamplerAddressMode.Repeat,
    AddressModeW = SamplerAddressMode.Repeat,
    CompareEnable = false,
    AnisotropyEnable = false,
    MipLodBias = 0f,
    MinLod = 0,
    MaxLod = 1000
};

var mySampler = new Sampler(GraphicsDevice, mySamplerState);

There are three kinds of sample filters: Nearest, Linear, and Cubic. Nearest is the cheapest and doesn't do any kind of filtering. This filter is ideal for upscaling pixel games - Linear will make your pixel art look terrible. Cubic is the most expensive filter but upscales and downscales in decent quality.

MinFilter describes which filter to use when the result image is smaller than the sampled image - MagFilter, likewise, is used when the result image is larger.

Anisotropic filtering can be used in conjunction with mipmaps to reduce aliasing and blur on obliquely-rendered textures. Explaning this is beyond the scope of this tutorial but I encourage you to look into the technique if you are planning to make 3D games.

When you look up pixels using a sampler, you generally look them up using coordinates in the range of [0, 1]. This coordinate space is often referred to as "texture coordinate space" or "UV space". SamplerAddressMode refers to the behavior that will occur if the texture is sampled outside of [0, 1] coordinates. ClampToEdge will just take the pixel at the nearest edge. Repeat will loop the image, and MirroredRepeat will mirror the image.

U-coordinates are horizontal, V-coordinates are vertical, and W-coordinates correspond to depth. You can use different address spaces for each of these directions.

The same sampler can be used in conjunction with as many different textures as you like. We will discuss this more when we get into "binding" resources using command buffers.

There are some common SamplerStates that are provided for you, for example SamplerState.PointClamp. Have a look at the SamplerState definition to see them all.