Some simple XNA/HLSL questions

Question

I\'ve been getting into HLSL programming lately and I\'m very curious as to HOW some of the things I\'m doing actually work.

For example, I\'ve got this very simple shad

Answer 1

mySampler is assgined to a sample register, the first is S0.

SpriteBatch uses the same register to draw textures so you have initilized it before for sure.

this register are in relation with GraphicDevice.Textures and GraphicDevice.SamplerStates arrays.

In fact, in your shader you can use this sentence:

 sampler TextureSampler : register(s0);

EDIT:

if you need to use a second texture in your shader you can make this:

 HLSL
      sampler MaskTexture : register(s1);

 C#:
      GraphicsDevice.Textures[1] = MyMaskTexture;
      GraphicsDevice.SamplerStates[1].AddresU = TextureAddresMode....

Color0 is not a registry and does not hold the current pixel color. It's referred to the vertex structure you are using.

When you define a vertex like a VertexPositionColor, the vertex contains a Position, and a Color, but if you want to define a custom vertex with two colors, you need a way to discriminate between the two colors... the channels.

The number suffix means the channel you are referring in the current vertex.