title: Confusion about MSAA
body: <p>I was researching about MSAA and how it works. I understand the concept how it works and what is the idea behind it. Basically, if the center of triangle covers the center of the pixel this is processed ( in case of the non-msaa). However, If msaa is involved. Let's say 4xmsaa then it will sample 4 other point as sub-sample. Pixel shader will execute per-pixel. However, occlusion,and coverage test will be applied for each sub-pixel. The point I'm confused is I imagine the pixel as little squares on the screen and I couldn't understand how sub-sampling points are determined inside the sample rectangle. How computer aware of one pixels sub-sample locations. And if there is only one square how it sub-sampled colors are determined.(If there is one square then there should be only one color). Lastly,How each sub-sample might have different depth value if it was basically same pixel.
  Thank you!</p>