The problem was that I wasn't clearing D with Color.Transparent for every sprite. So, when I tried to overlay D onto P, the alpha channel didn't work as expected. Changing the code to this made it work:

for all sprites:
{
    graphicsDevice.SetRenderTarget(D);
    graphicsDevice.Clear(Color.Transparent);
    &lt;draw sprite i&gt;

    graphicsDevice.SetRenderTarget(P);
    &lt;Draw D&gt;
}


RenderTarget2D behavior in XNA
Specifically, I am looking to describe a person whose only purpose is to help others, not caring about what happens to  himself or herself (physically or otherwise), though without actively seeking pain.
