modern games draw the sky last because it's pretty expensive and we want to depth reject as many pixels as possible. however there's a problem when using msaa. Because msaa will give the edge of objects the blended color between the object and its background (the clear color), and the edge also has a depth that's similar to the object. When drawing the sky, it's depth tested against the edge, and hence is not drawn on it since the sky is further than the edge. This leaves a very annoying edge with some component of the clear color around objects. What's the best way to solve this?