title: 2D Pixel Shader removing alpha channel from color
body: <p>So, I'm trying to make a game in XNA, and I'm applying a pixel shader to my level so I can add effects to the gameplay screen. The shader itself is working nicely, but it has one flaw that really pushes back performance. As long as the shader is active, anything I draw to the screen acts as though it was drawn with it's alpha channel at the maximum. I'm drawing a lot of things using XNA's built in <code>Color</code> class, and much of it has varying alpha. However, the shader seems to ignore all of this. This occurs even if I just return the source from the shader.</p>
  
  <p>I've seen a few possible solutions. The first of these was to draw to a RenderTarget2D and, while this did solve this issue, it caused more serious problems with alpha that I don't even want to go into.</p>
  
  <p>I have seen a few people claim that multiplying the colours by the alpha value in the shader seems to help, but that made absolutely no difference, which suggests to me that the alpha value input is always being read as 1.</p>
  
  <p>Here are some images to illustrate my problem:</p>
  
  <p><img src="https://i.stack.imgur.com/sgZqy.png" alt="This is the result with the shader active"><img src="https://i.stack.imgur.com/UCkKD.png" alt="This is what it&#39;s supposed to look like"></p>
  
  <p>Hopefully, someone knows how to resolve this.</p>