I want a texture with 4 8bit channels so i define it as DXGI_FORMAT_R8G8B8A8_UINT. Is this the correct format i should be using? And how do i sample it in a shader because what i'm doing is not working:
float3 tID = Alphamap.Sample(Sampler, input.uv).rgb;
I'm assuming it's because floats are 32 bit, but i couldn't find an HLSL scalar type that's 8 bit...
Your code is absolutely correct. The sampling hardware converts the 4 * 8-bit texture into 4 * 32-bit float (or what is the float precision hardware is using).
However, the texture format DXGI_FORMAT_R8G8B8A8_UINT isn't correct. the ending should be _UNORM.
Cheers!
Worth noting is that the 8-bit RGBA values can be normalized (i.e. 0 to 255 => 0.0 to 1.0) when presented to the shader by the sampler for different format modifiers.
See the formatting table at the bottom of this page: http://msdn.microsoft.com/en-us/library/windows/desktop/bb173059%28v=vs.85%29.aspx
