The first image shows an image with no antialiasing
The second image highlights the pixels that have been selected for further sampling.
The third image shows the results of adaptively sampling a 3x3 uniform grid for each highlighted pixel. Rendering time: 1.3s
The fourth image shows the same scene but rendered with non-adaptive 3x3 supersampling. Notice the similar quality level but nearly double the rendering time. Rendering time: 2.6s